III|e §. p. ^tU pbrarg ^ortli ffiarolina ^tate College QK4T C75 Date Due uOJl^ TBec^pl TTnT\ HEERiMG J qV£J^ 17525 A^Dli^d^-^conomlc. 17523 LIPPINCOTT'S FARM LIFE TEXT SERIES EDITED BY KARY C. DAVIS, Ph.D. (Cornell) Applied Economic Botany LIPPINCOTT'S FARM MANUALS Edited by K. C. DAVIS. Ph.D. SECOND EDITION REVISED PRODUCTIVE SWINE HUSBANDRY By GEORGE E. DAY, B.S.A. $1.75 net. THIRD EDITION REVISED AND ENLARGED PRODUCTIVE POULTRY HUSBANDRY By harry R. lewis, B.S. $2.00 net. SECOND EDITION REVISED PRODUCTIVE HORSE HUSBANDRY By carl W. gay, B.S.A. $1.75 net. . PRODUCTIVE ORCHARDING By FRED C. SEARS, M.S. $1.75 net. THIRD EDITION REVISED PRODUCTIVE VEGETABLE GROWING By JOHN W. LLOYD, M.S.A. $1.75 net. SECOND EDITION REVISED AND ENLARGED PRODUCTIVE FEEDING OF FARM ANIMALS By F. W. WOLL, Ph.D. $1.75 net. SECOND EDITION COMMON DISEASES OF FARM ANIMALS By R. a. CRAIG, D.V.M. $1.75 net. SECOND EDITION PRODUCTIVE FARM CROPS By E. G. MONTGOMERY, M.A. $1.75 net. SFCOND EDITION REVISED PRODUCTIVE BEE KEEPING By frank C. PELLETT $1.75 net. PRODUCTIVE DAIRYING By R. M. WASHBURN $1.75 net. INJURIOUS INSECTS AND USEFUL BIRDS By F. L. WASHBURN, M.A. $2.00 net. PRODUCTIVE SHEEP HUSBANDRY By WALTER C. COFFEY $2.50 net. 2 I ffl "3 Farm Life Text Series EDITED BY K. C. DAVIS, Ph.D. (Cornkll) APPLIED ECONOMIC BOTANY BASED UPON ACTUAL AGRICULTURAL AND GARDENING PROJECTS BY MELVILLE THURSTON COOK, Ph.D. RUTGERS COLLEGE, NEW BRUNSWICK, N. J. 14s ILLUSTRATIONS PHILADELPHIA AND LONDON J. B. LIPPINCOTT COMPANY COPYRIGHT, I919, BY J, B. LIPPINCOTT COMPANY Electrotyped and printed by J. B. LippincoU Company The Washington Square Press, Philadelphia, U.S.A. PREFACE There are already so many text-books on botany that the anthor has long hesitated to present another to the educational public. The study of botany has developed very rapidly in the past quarter of a century and as a result we have a gi-eat variety of text-books representing an almost equally great variety of methods of presenting the subject. Yet, we meet with a con- tinuous series of complaints against the poorly adapted sec- ondary text-books for teaching in secondary schools, technical schools and colleges. The teacher in the secondary school says that text-books are written by college professors who do not understand the problems involved in secondary education ; the teacher in the technical school complains because the students from the secondary schools cannot correlate the botany with related subjects; the college professors complain because of the mechanical methods used in the secondary schools which dis- courage rather than encourage further study of the subject by those who enter college. Having sei-ved for a time as a high-school teacher, the author has some realization of the difficulties of the secondary schools. As a college professor he has some appreciation of the keen dis- appointment felt by those who conduct the Freshman entrance examinations, and who try to teach botany to the college students that come to college with ideas of botany obtained from their training in the secondary schools. By experience, he has learned that the results of the entrance examinations are fully as un- satisfactory when the questions are prepared by the high-school teachers as when prepared by himself. The placing of the responsibility for this condition is a c vi PREFACE problem not easily solved. But the writer is inclined to believe that the secondary school is trying to do too much, trying to do work beyond the pupils, trying to do work that should be left for the college. We give the pupils compound microscopes, which is much like giving them a complete set of surveying instruments for use in the study of elementary arithmetic. We try to teach facts when we should teach fundamental principles, close observation and accuracy. We try to teach scientific names when we should teach simple methods of experimental work. In this little work the autlior has aimed at three things, viz.: (1) A brief statement of the recognized facts and prin- ciples concerning jjlants and plant growth usually given in text- books for secondary schools. (2) A list of simple exercises and suggestions for observations which the pupil can conduct with- out great difficulty and which will demonstrate many of the statements given in the book. ( 3 ) A list of questions which are intended to be suggestive to the pupils and to encourage further studies. The title, " Applied Economic Botany," implies first, that it is intended as a guide to experimental work in the study of plants, such as should be carried on in any high school, and second, that it is intended as a preliminary work to the agricultural studies which are now recognized in many high schools. The author has endeavored to make the work so flexible that it may be used in schools regardless of the amount of time devoted to the subject, the available laboratory space and equip- ment. The author has also been mindful of the fact that the course in botany in the secondary school should meet the needs of very different classes of pupils — those who study it as one of the requirements of the curriculum and to whom it must be primarily a cultural subject, those who study it as a prepara- tion to agriculture and horticulture, and those who may use it PREFACE vii to fiillill one of the college entrance requirements. The same course can and should serve all of these purposes in the same manner that the courses in mathematics and Eng-lish literature serve those who go direct from the secondary schools into the trades, or business houses, or professions, or to college. The manuscript has been submitted to both high-school teachers and college professors for criticisms and suggestions and manj changes have been made in an effort to meet the requirements of both classes of teachers, although the general plan of the work has not been changed. Many of the illustrations in this book are purely diagram- matic and are intended as guides and not completed work to be copied by the pupil ; many others are from drawings made by the author's students and are such as can be readily made by most high-school pupils. A text-book in botany is a guide, and it is neither neces- sary nor desirable that the class should follow it in all details. The teacher should select such exercises in this or other books as may suit the purpose and should make such variations and additions as may be desirable. Supplementary reading along the lines of plant geography, and economic botany, observations in field, forest and stream, and home studies in the growing of plants should be encouraged. The success or failure of the course in botany is more dependent on the teacher than on the books, laboratories and equipment. A good teacher is more necessari/ than hooJcs, lahoratories ayid equipment. The acquire- ment of industry, enthusiasm, methods of work, self-reliance, close ^.observation and accuracy on the part of the pupils are much more desirable than much of the so-called knowledge that consists of disconnected or questionable facts. Mel. T. Cook. Rutgers College, New TJRtTNswicK, N. J. CONTENTS Preface v Introduction ix Equipment and Methods xiii PART I.— PLANT LIFE CHAPTER I. Seeds and Seedlings 3 II. Roots 18 III. Stems and Buds 31 IV. Leaves 45 V. The Flower 54 VI. Reproduction 74 VII. Fruits and Seeds 83 VIII. Anatomy op Stems, Roots, and Leaves 93 IX. Chemical Composition of the Plant 105 X. Plant Foods and Plant Growth Ill XI. The Gymnosperms 121 XII. Ecological Relations 126 XIII. Forestry 134 XIV. Plant Diseases 139 XV. Plant Breeding 147 XVI. Weeds 150 XVII. Pteridophytes 158 XVIII. Bryophytbs 164 XIX. THALLOPHYTiES 169 XX. Bacteria 177 PART II.— MOST IMPORTANT FAMILIES OF ECONOMIC PLANTS, WITH SPECIAL EXERCISES XXI. Important Families of Plants 183 Mustard — Crucifer^e 185 Violet— VioLACE^ 189 Mallow — Malvaceae .• 191 Sterculia — Sterculiace^ 193 Flax — Linace.e 193 Rue — RuTACEiE 195 ix X CONTENTS Vine — Vitace^ 196 Soap Berry — Acerace^ 198 Pea — Legdminose^ 199 Rose — Rosacea 204 Saxifrage — Saxifragace^ 211 Gourd — Cucurbitace.e 211 Parsley — Umbellifer.e 215 Madder — Rubiace.e 215 Sunflower — Composit.^ 216 Heath — ^Vacciniace^ 217 Convolvulus — Contolvulace.'g 218 Nightshade — Solanace^ 219 Goosefoot — Chenopodiace^ 221 Buckwheat — Polygon ace^ 222 Nettle — Urticace^ 223 Walnut — Juglandace^ 225 Oak — Cupulifer^ 226 Willow — Salicace^ 227 Banana — Zingibreace^ 227 Lily — ^LiLiACEiE 228 Grass — Gramine^ 228 XXII. Special Exercises with Plant Families 234 Appendix — References 243 INTRODUCTION ^ 6 7- Botany is a science of the very greatest importance but one which is frequently misunderstood and neglected in our educational system. To many people, it means the learning of scientific names of plants, but this is an incorrect idea. Botany is neither the study of flowers nor the learning of scientific names. Botany is the study of plants and plant life. It is of great importance because plant life is absolutely necessary for the existence of all animal life, including mankind. We are dependent either directly or indirectly upon the plants for food, clothing, building materials, fuel and many other necessaries. We use plants, or animals which have fed on plants, for food. Every article of food on the table, except the salt and water, is derived from plants or from animals which are dependent on plants for food. We use cotton and linen, and many other vegetable fibres, for clothing and many other purjxtses; and we also use wool and silk which are derived from animals that have fed on plants. We use wood for building purposes, for making furniture and parts of tools and implements, and for the making of paper pulp. We use wood and coal and oil, which are derived from plants, for fuel. And finally, we go to the plants for about 90 per cent of the dl1^gs to relie\'e our aches and pains and restore us to health. ^ When we once realize our absolute dependence on plant life, we also begin to think something about the number of industries that are dependent on plants. The farmers, the horticulturists, the gardeners, the florists and the foresters are not the only people who are dependent on plaaits for a livelihood. Practically all manufacturing industries are dependent on plants in some form; for fuel if for nothing else. Even the electric establish- ments must use fuel to> run the niachiiierv for t]m u'eneration of XU INTRODUCTION _eLaetarrcrty. When we think of these things we wonder why it is that man has not given more attention to this jjrimarv source of life, health, wealth and happiness; why he has not given more attention to increasing it. The answer lies in the fact that nature is good to us ; nature has supplied man with the neces- saries and more, and man has been satisfied. But with the in- creasing population it will become more and more necessary for man to study plants and plant life and to learn the secrets of nature which \nll enable him to increase the production of val- uable plants. Plants have influenced the migTation of man. In the account of his journeys of discovery and exploration he has always given much attention to the character of the plant^life. And most of the permanent settlements of importance have depended on the character of the plant life and the possibilities for agriculture. Big factories may have been located where the water power was good, but they must also be accessible to the raw materials to be used ; or they may have been located near the gTeat beds of coal, oil or natural gas and in that case they were dependent upon the plant products of past ages. How- ever, the great migrations of the world have always been along the lines of great plant growths, and the early settlements in America and the rapid progTess of the American people, with which you are familiar, are ample proofs of these statements. But this is not all ; the great joy of life is in life itself. To fully enjoy the life within us we must take pleasure in the life around us. The joy of the country, of the forests and plains, the mountains and valleys, of the parks and gardens, }i^not only in their beauty but in the appreciation of the value of the plant life which makes them beautiful. Botany cannot be studied like most subjects ; it does not con- sist in committing facts. It cannot be learned from books, for there is no botany in books. Books contain a feiv plans and methods for studv ; a fev records of observations and studies /V INTRODUCTION xiii already made; a few facts already learned. The plans and studies may be changed to-morrow ; the records of observations and studies will be increased ; and many of the supposed facts may prove to be errors and be supplanted by other statements. ^Q,_5ve must not study books ; we can use the books as guides, but we must study the plants themselves. Louis Agassiz said, ''' Study Nature, not Books" ; and in studying botany, we should stud^^ t4ieaiati«'©-int or cap downwards. Note that it is covered with a tliin horny coat which can be removed. Within the groove is the young plant or embryo with the root pointing downward. Tlie stem is partly surrounded by a single leaf or cotyledon The entire embryo is surrounded by starch. The remainder of the grain consists primarily of two other forms of starch varying in amount in the ditierent varieties. Cut some of the grains lengthwise and some in cross section, and examine the relationsJiip of the various parts. Make a series of drawings or diagrams to show the preceding {wints. 4. Write a comparative description of these three types of seeds. 5. Examine a number of other seeds and group them with some of the above groups or types. C. Absorption of Water. — Weigh a small quantity of dry seeds, place in water for a few hours and weigh again. What is the percentage of loss or gain in weight? 7. Fill a tall bottle or tube with dry seeds and add enough water to cover them. Mark the level of the water at the end of one, two, three, four and five hours respectively. Explain. 8. Fill a test tube or a bottle or a glass fruit jar with dry beans, tie a strong cloth over the top and immerse in water over night What is the result? Why? 9. Eemove the seed coats from a quantity of dry beans and weigh without the coats; weigh out an equal amount of dry beans without removing the seed coats. Put the two lots in water for on© hour. Compute changes in weight. Put in water for an additional hour and again com- pute changes in weight Explain. 10. Take two lots of dry bean» of equal weight. Cover the micropyles of one lot with varnish or sliellae and put both lots in wet sand for two hours. Weigh each lot and compute) changes in weight. Explain. 11. Germination. — Plant a quantity of corn, beans, peas, melon, squash, cucumber and such other seeds as may be desirable, in clean sand. Remove a few seeds at intervals of three or four days. Make drawings, label the parts and write descriptions and comparisons. (Or, plant the seeds at intervals of three or four days for two or three weeks and then study the seedlings at various stages of growth at the same time. ) 12'. Cut a small slice off one side of several grains of corn. Ger- minate these with an equal number of uninjured grains between sheets of blotting paper. Is tliere any difference in time of germination? Why? 1.3. Influence of Moisture, Heat and Light. — (a) Plant two or three kinds of seeds in wet sand in a flower pot and keep in a warm, well-liglited place. 16 SEEDS AND SEEDLINGS (b) Plant as in (a) but keep in a warm, dark closet. (c) Plant as in (c) but keep in . Compare the cotyledons of the common bean and the castor oil plant. 27. Describe the opening of the seed coats of the bean, castor oil plant and other seeds. CHAPTER II ROOTS We all know that plants have roots, bnt they are usnally buried in the ground and thus hidden from sight and are not especially attractive. Therefore, most persons prefer to study the more prominent and pleasing parts of the plant. How- ever, no part is of greater importance to the plant as a whole than the root system. When the seed sprouts, the root is the first organ of the embryo to break through the seed coats. (Figs. 2 d, 4, 6 and 7 a.) It grows downward, away from the light, but into the soil which contains the food and water. This ten- dency to go downward is called geotropism. The soil should contain the necessary supply of food and moisture, and should be of such character that the roots can penetrate it readily if the plant is to make its normal growth. But we shall learn later that all plants do not require the same amounts of moisture, nor the same amounts and kinds of food. The farmer cultivates the soil for his crop plants and thus aids the plants in the work necessary for their growth. Extent of Roots. — The root usually grows very rapidly, and when the entire root system is compared with the parts of the plant above ground, it is found to be much more extensive than we have ever imagined. When we pull a plant from the soil a very large number of the roots are broken off and left be- hind. Therefore, we get a very imperfect idea of the root system and its ramifications in the soil. But if a plant is grown in a pot of loose soil, and this soil carefully washed from the roots we begin to have some slight idea of the very great value of this part of the growing plant. It has numerous branches, 18 GATHERING FOOD AND MOISTURE 19 many of which have a delicate hair-like growth. The total length of all the roots of some plants may be many times the total of the stem and branches. The total length of all the roots of a mature oat plant are said to aggregate 154 feet, and those of a mature corn plant 1320 feet. Of course, no one root is likely to be more than a few feet in length. However, some plants are known to produce individual roots of considerable length. The alfalfa is said to produce single roots as much as 31 feet in length and the mesquites of the dry western plains are said to produce individual roots of as much as GO feet in length. The greater the root surface, the greater the amount of food and water that can be secured by the plant. Of course, an increase of the root system is usually necessary to an in- crease of the part above ground. The roots serve many purposes in the life of the plants, but these duties are somewhat variable for different plants. The most important functions are as follows : anchorage, gathering of water and food, storage of water and food, and in some cases for climbing. The roots serve as an anchor by which the plant is held in place. When we try to uproot a plant or think of the terrific wind storms to which our trees are frequently exposed, we can appreciate the importance of a secure anchorage. Some of the large trees of California are said to be thousands of yeaxs old and, after battling with the stonns of ages, are still standing, objects of great admiration. Gathering Food and Moisture. — We know that the roots are organs through which water and much of the food materials enter the plant, but we have very little idea of the amount of water and food necessary for plant growth. Our land plants require enormous quantities of water (Page 105), which must enter through the roots. Therefore, it is necessary for the roots to spread through the soil in such a manner as to reach 20 ROOTS both water and food. The soil food is dissolved in the water, and the two usnally enter the plant at the same time. The thick, lieshj roots which are characteristic of some plants, such as the turnip, beet and radish, serve for the storage of food and water. Roots of this kind are used extensively for food by man and animals. The roots of some plants, such as the poison ivy, servo for climbing. Forms and Arrangements of Root Systems. — The roots of a plant are not as irregular as many persons suppose ; they assume forms and arrangements which are nearly as definite as the parts above ground. These forms and arrangements are just as characteristic of many plants as the stems, leaves, flowers and fruits. The roots of some kinds of plants go deep into the soil, while the roots of other kinds spread out, forming a mat just below the surface. However, the arrangement of the roots of plants of the same kinds will vary somewhat, with the character of the soil. The most important soil characters which influence the arrange- ment of roots are texture, depth, fertility and amount of mois- ture content. In general, it may be said that in shallow soil the roots will spread near the surface of the ground, while in deep soil they will tend to lie deeper; in rich, moist soil they will be short and branching, while in poor, dry soil they will be long and with few branches. However, some plants by nature tend to spread their roots near the surface, while others, like alfalfa, tend to go deep into the earth and are, therefore, espe- cially well suited for certain soil conditions. Some crops require much deeper and richer soil and much more thorough cultiva- tion than others. The potato and other plants with large, fleshy, underground structures require loose, deep, rich soil to thrive and give the best results. A knowledge of this relationship between root systems of plants and soil conditions is of very great value in selecting crops for difl"erent localities. FORMS AND ARRANGEMENTS OF ROOT SYSTEMS 21 The roots of some plants are fibrous (Figs. 9, 10 and 13), and in large plants very woody and hard, while the roots of other plants are thick and fleshy. (Figs. 11 and 12.) The fibrous roots branch irregularly and serve for anchorage and also for the entrance of water and dissolved food materials. Fig. 9. — A grass plant showing the fibrous root system. Fig. 10. — A bean seedling showing the bac- terial nodules on the roots. The fleshy roots, in addition to this work, also serve as places for storage of large quantities of foods. Man and animals take advantage of these stored products and use the roots of many plants for food. However, this food is stored in the roots for the future use of the plants themselves and is usually an import- ant factor in their production of flowers and seeds. (Page 52.) Some plants use this stored food the same season that it is accumulated, while others hold it in reserve for one or more 22 ROOTS years. The radish is a plant in which the food is used for seed production the same season that it is stored. The turnip develops the fleshy root one year and uses it for seed production the second year. Food for Man. — The supply of stored food in the roots of many plants makes them valuable for food of man and other Fig. 11. — Carrot showing fleshy root. Fig. 12. -Sweet potato showing cluster of fleshy roots. animals if used before they start to form the shoot for flower and seed production. But if we wait until this shoot is well advanced, we find the root becoming dry and pithy, owing to the loss of moisture and food which has been passed on into this new growth. In some plants, this storage for future use is performed by the stems or leaves. (Page 51.) The sweet potato (Fig. 12) is a plant which seldom produces seeds in our northern latitude, but uses the accumulated food of the large AERIAL ROOTS 23 fleshy roots for the inimediate production of new plants or slips. Sometimes, new plants are also produced directly from fibrous roots, as in the case of the poplar, plum, etc., but as a rule new plants are not produced from the roots. Length of Life.- Plants which live but one year, as in the case of the radish are known as annuals; those that live for tw^o Fig. 13. — Corn plants sliowing the aerial roots. years, as in the case of the turnip, are known as biennials; while those that normally live for several years, as in the case of trees, are known as perennials. Aerial Roots. — Eoots are frequently borne on parts of the stem above the ground, and are known as aerial roots. (Fig. 13.) These roots tend to reach the soil and serve as prop roots and help to support the plant against wind storms. They are well developed on the lower part of the corn, and are especially prominent on those plants which have not been tilled properly. 24 ROOTS The Banyan tree of the tropical East Indies produces roots from its branches which tend to reach the soil and finally assume the character of tree trunks. Some plants, kno%vn. as epiphytes, especially abimdant in warm, moist climates, often produce aerial roots which never reach the soil but spread out into the moist air and serve for the absorption of water. The orchids of tropical countries, and the so-called Florida moss of our own Southern States are striking examples of epiphytic Fig. 14. — Cross-section of stem showing dodder attached by haustoria or parasitic root. plants. The orchids in the colder climates are rooted in the soil. The aerial roots may also serve for climbing on trees, fences or buildings, stone walls and other firm objects. Climbing plants are frequently injurious to trees, not only because their roots penetrate the minute crevices, but also because they retain the moisture and make favorable co-nditions for organisms which cause decay. They are also injurious to wooden structures on which they are allowed to grow, in that they retain moisture and cause decay. Parasitic Roots. — Some plants feed upon other plants by means of roots which penetrate them. They are called parasites, and their roots parasitic roots or haustoria. The mistletoe of the South and the common dodder (Fig. 14) which is much fHOfERTT UBKARY Ji. C. State Colkgi STRUCTURES 25 more widely distributed throughout the country are good illustra- tions of this type of roots. Aquatic Roots. — Some floating plants produce roots which never penetrate the soil. They are known as aquatic roots and absorb water and the yarious food substances in solution which are necessary for plant growth. The very small but widely distributed duck weeds and the much larger water hyacinth of the South are excellent examples of floating plants. However, many aquatic plants, such as the pond lily, cat-tails, etc., have roots which penetrate the mud, while the plant either floats or stands upright. Structures. — Roots are made up of three parts, a central cylinder composed pri- marily of woody tissue and surrounded by a sheath or cellular cortex, and covered with a very thin epidermis or skin-like coating. (Fig. 15.) They grow in length much more rapidly than in thickness and the very delicate tip is protected by a mass of cells known as the root cap. All parts of the root do not elongate with equal ra- pidity. There is a zone just back of the tip in which the growth is most rapid.' The tips of roots are soft and delicate and easily broken, yet they must exert an enor- mous force which we cannot appre- ciate. The surface of the young roots, just back of the tip, is covered with numerous very delicate root-hairs or trichomes. (Figs. 4, 16 and 19.) These root-hairs are very numerous and should be studied on very young plants that have been grown in Fig. 15. — Diagramm- atic longitudinal sec- tion of a root tip; a, central cylinder; c, cortex; e, epidermis; r. c, root cap. 26 ROOTS a germiuator, and also on plants that have been grown in loose soils. They grow between the very fine particles of soil. If the plant is pulled from hard soil they are torn olf, but if pulled from loose, wet soil, they are retained and the soil clings to them. In order to understand them it will be necessary to study them with a microscope. Fig. 16. — .Seedling showing Fiu. 17. — Cross-section of rootlet showing root-hairs, soil held by root-hairs. Work of Root-Hairs. — Each root-hair is a thin-walled cell containing living protoplasm and cell sap. This living proto- plasm has the power of absorbing water by osmosis, causing the cells to become very much expanded or turgid. The excess of certain substances in the soil may cause an exosmosis or with- drawal of water from the roots and thus injure or even kill the plant. This explains one reason why certain soils may be AIDED BY OTHER ORGANISMS 27 unsuited for certain plants and also how the farmer may injure his crops by using too much of certain fertilizers or by the im- proper mixtures of the fertilizers with the soil. The root-hairs persist for a very short time and then perish, but new ones are produced near the growing tips. The number of root-hairs varies with the amount of water in the soil. They are more numerous in dry than in wet soils. (Figs. 17, 18 and 19.) Fig. 18. — Showing attachment of root- hair to epidermis. FlQ. 19. — Showing relation of root-hair to soil particle. Aided by Other Organisms. — Plants are frequently facil- itated in securing their food by other organisms. Dead plants, dead animals and manures must undergo a decay before they are sources of available food for most plants. This decay is caused by bacteria and fungi. (Page 172.) Certain bacteria also aid the plant by taking the nitrogen from the air and fixing it in such a manner as to make it available for plant food. (Page 117.) 28 ROOTS Roots of Plants Require More or Less Air. — The securing of this air is facilitated in many of our cultivated plants by drainage and by cultivation of the soil, thereby keeping it loose so that the air penetrates it readily. But plants growing in a state of nature have various parts and organs through which the necessary air is secured. Many aquatic plants, such as pond lilies and cat-tails, have air passages by which the air passes from the parts exposed to the air to the submerged parts. The swamp cypress has peculiar upward root growths known as " knees," which project above the surface of the water and serve for the absorption of oxygen. Many forest trees have root growths extending above the surface of the soil which serve for the same purpose. The filling in around trees which is frequently necessary in making grades is injurious because it prevents the air from reaching the roots. EXERCISES WITH ROOTS 1. Direction of Growth of Roots. — Sprout a nvimber of seeds and suspend in a moist chamber on lon^- ])ins or by means of threads so that the root tips will point in different directions. Examine from day to day and note the direction of growth. Small moist chaml>ers can be made by putting a small amount of water in a wide bottle or! glass jar; run a hat pin through tlie cork for supporting seeds. 2. Direction of Growth in Soil. — Sprout a number of seeds and plant in wet sand in such a manner that the root tips point in different direc- tions. Examine one a few days later and note the direction of growth of roots and stems. 3. Growth Against Resistance. — Partly fill a small cup with mer- cury. Pour a little water on the surface. Fasten a germinated seed in such a manner that the root tip rests on the mercury. Inclose in a moist cham- ber for 24 hours. Has the root ti]) penetrated the mercury? Does this require force? 4. Geotropism or Direction of Root Growth. — Sprout a number of beans in sphagnum moss or other loose material that will insure the forma- tion of straiglit roots. Mark the roots into short, equal sections, using India ink. pin them to corks and place in large moist chambers * in such * Moist chambers can be made by lining large Ijattery or other glass jars with wet filter paper and covering so as to prevent excessive evaporation. EXERCISES WITH ROOTS 29 a manner that tlicy will point in various directions. Examine at tlu- end of 24 hours and again at the end of 48 houra Note the direction of growth, the point at which curving begins and where the curvature is greatest as indicated by the marks and the point at which the greatest growth occurs. 5. Examine the root system of a growing bean, castqr bean, or sun- Hower. Note the tap root, the mode of branching, the location of oldest and youngest branches, size and shape of tap root and branches. Make drawings or diagrams. 6. Examine the root system of growing corn, wheat or oats. Com- pare the root system with tliat in Ex. 5. Make drawings or diagrams. 7. Examine the root system of a growing beet, turnip or radish. Note the tap root and its branches Compare with that in Ex. 5. Make drawings or diagrams. 8. Examine the root system of tlie dahlia or sweet potato. Compare with that in Ex. 7. Make drawings or diagrams. 9. Examine the root system of English ivy or some other plant or plants in which the roots serve for climbing. Note their location, branch- ings and general character. Make drawings or diagrams. 10. Region for Root-hairs. — Sprout a niunber of grains of corn, okra, radisli seed, clover seed, or white mustard, between wet blotting paper until the roots are abouti one and one-half inches in length. Note the region on which the root-hairs occur. Examine the root-hairs under a compound microscope, or strong hand lens. 11. Soil Held by Root-hairs. — Plant seeds in fine, sandy soil. After two weeks wet the soil thoroughly and very gently remove the plants. Note the manner in which the soil is held by the root hairs. 12. Roots from Willow Twigs. — Ctit a niunber of willow twigs about twelve inches in length and put in a jar of water so that about half the length will be covered. Put part of them' upside-down. Use an earthen jar or a glass jar covered with black paper so as to exclude the light. Examine from time to time and note the formation of roots. Where are they located and what is the direction of growth? 13. Osmosis with a Thistle Tube. — Make an artificial root-hair by covering the large end of a thistle tube with an animal or plant mem- brane, piece of intestine (sausage covering) or bladder, fill the bulb with a thick syrup (mola.^ses) and invert in a jar of water so that the two fluids stand at the same level. Examine after a few* hours^ and note the rise of the fluid in the tube. This passing of a fluid of less density through an animal membrane into a fluid of greater density is called osmosis. (Pages 112 and 11.3.) 14. Osmosis with an Egg. — Remove the shell without breaking the skin from the large end of an egg over an area about the size of a dime. In the same manner remove a small bit of shell from the small end over 30 ROOTS an area about one-eighth of an inch in diameter. Run a glass tube through a small section of a wax candle and directly over the small openin};. Now push the wire down the tube and puncture the membrane at the small end of the egg. Fill a wide-mouthed bottle level full of water and set the egg in the top. (Fig. 80.) Note and explain the rise of water in the tube. 15. Osmosis with a Fleshy Root- — Cut a slice from the upper part of a carrot or other fleshy root; hollow out the centre of the root and fill with sugar. Let stand for twenty-four hours. What has occurred? Explain. IG. Cut thin strips, about one-eighth inch thick, of a fleshy root and place in salt water for a few hours. Examine and then place in distilled water for a few hours. Examine and explain. QUESTIONS 1. VVliere do we find the root system of the plant? 2. What do you understand by geotropism ? 3. What are the characters of the soil that make it suitable for plant growth ? 4. What can you say about the different types of root systems of plants ? 5. What are the functions of the roots? 6. Is there any difference in the arrangement of the root systems of plants ? Explain. 7. Upon what is the variation of the root system dependent? 8. What is the difference between the root system of the radish and that of the turnip? What functions do they serve? 9. Give a list of plants whose roots are used for food by man and livestock. 10. Define and give examples of annuals, biennials, and perennials^ 11. What is the difference between aerial and epiphytic roots. 12. Name some plants with parasitic roots. 13. Name some plants with aquatic roots. 14. Name and locate the three parts of a root. 15. Explain osmosis. 16. Why are some fertilizers injurious to plants? 17. How does air reach the roots of plants? How can the farmer aid plants to secure air? 18. What is the general direction of root growth? Of stem growth? CHAPTER III STEMS AND BUDS The stem is that part of the plant which connects the root with the leaves. The most common types of stems of seed- bearing plants are above ground and serve to support the foliage and flowers. They usually show more or less well-defined divi- sions into nodes (joints), and internodes as indicated by branches, leaves and leaf scars, buds and bud scars. (Figs. 20 and 21.) They produce branches at the nodes more or less regularly. At the points where the new season's growth begins we find a number of scars very close together. (Fig. 20.) By examining the scars we can usually determine the amount of growth of the twigs for several years past. There are two well-defined types of stems, the exogenous (Fig. 22 a), or the outside growing, and the endogenous (Fig. 23 a) or inside growing. The former is much more abundant than the latter, and the two can be readily distinguished by cut- ting them in cross sections. In both cases the stems are com- posed of hard, woody bundles surrounded by a softer substance which is covered by the bark or protective covering. The ar- rangement of these bundles is quite difl^erent in the two classes. In the exogenous stems (Fig. 22) the bundles are almost always arranged in a circle and the strength of the stem depends, in a large measure, on their compactness. Such stems will in- crease in diameter as long as the plant is alive and gi'owing. This increase in diameter is due to the formation of a layer of wood just outside the last year's growth of wood. This very thin layer of cells in which the new growth is occurring is known as the cambium. These annual layers are so distinct that 31 32 STEMS AND BUDS they can be readily seen on the cut ends of tree trunks, with the naked eye, and are known as annual rings. (Fig. 24.) All the dicotyledonous and coniferous jjlants have stems of this type. If you cut a cross-section of a soft, rapidly growing stem (be- gonia or geranium), you can see these bun- dles more or less well defined. If you cut a cross-section of a woody stem, you will readily recognize these bundles which are sep- arated by radiating lines. We find two types of endogenous stems. One which consists of a mass of soft, pithy tissue surrounded by a hard rind and con- taining scattered, woody strings known as fibro-vascular bundles (Fig. 23), and an- other which is of the same general character, but is hollow, and therefore the fibro-vascular bundles are forced into the form of a cyl- inder. All of the grass stems are endogen- ous; the corn which is a coarse grass, is a good example of the first type and the various grains and most common grasses are exam- ples of the second type. These fibro-vascu- lar bundles or woody strings can be readily recognized in the corn stalk. Stems in which the fibrous bundles are small as compared witH the surrounding ma- terials are soft and juicy, and are called herbaceous^ while those in which the bundles constitute the gi-eater part of the substance are called ivondy. Most of the strictly woody plants have exogenous stems and show rings. (Chapter VIII.) Stems Above Ground. — The aerial, or above-ground, stems; may be very short as in the case of the turnip or radish, in which FiQ. 20.— a, maple twig showing buds, leaf scar and annual growth ; b, horse chestnut twig showing same. STEMS ABOVE GROUND 33 it supports a mass of leaves very close to the root and is knowu as a crown or acaulescent stem, or it may be more or less elong- ated, as in the case of many herbaceous plants and trees. The elongated stems may ba erect, as in the case of trees, but extremely variable in size and form. Two well-defined types of Z:£:::^bi.'''>^,.,. ^^ri > .^'<^ Fig. 21. — Twig showing alternate buds. "^^^^^ the stems are the excurrent (Fig. 25), in which we find a tree with a central axis or trunk giving off numerous small branches, like the pine, and the deliquescent (Fig. 26), in which the main trunk sub-divides by branching and loses its identity as in the oak and elm. Stems belonging to either of these types vary Fig. 22. — a, cross-section of dicotyledonous Fig. 23. — a, cross-section of monocoty- steni ; b, fibrovascular bundle from same, ledonous stem ; b, cross-section of fibro- vascular bundle of same. greatly in the method of arrangement of the branches. Persons who have given some attention to this subject can recognize many trees by their style of branching. However, many elongated aerial stems cannot stand erect, but are decumheiit, or leaning, as in the case of many berry plants ; or prostrate, as in the case of those plants which trail 3 34 STEMS AND BUDS -YneA. fo-^ -arv-rvuVcvY Fig. 24. — Diagrammatic cross-eeotion of a trep stem showing the medullary ray and annular ring. Fig. 25.^Trees showing the excurrent type of stems. along the ground (ground ivy) ; or climbers, as in the case of many vines which cling to other plants, walls or buildings for support. Climbing may be accomplished by twining or by means of specially modified branches or stems (tendrils of UNDERGROUND STEMS 35 Fk;. 2(;.-Treo showiiiK It type of stem. grape), or by rootlets (poison ivy), or by modified leaves (clematis). Underground Stems. — Tlie stems of many plants are under- gronnd and are freqnently mistaken for roots. However, they 36 STEMS AND BUDS can be readily recognized by the fact that, like all stems, they are divided into more or less regular nodes and internodes, and the branching is ahvayni from these nodes and is, therefore, regular, while the roots are without nodes and branch irregularly. Fig. 28. — a, tulip bulb; b, same cut longitudinally to show short basal stem and fleshy leaf overlapping the single terminal bud. Numerous roots are frequently formed at the nodes of these underground stems. Underground stems may be divided into two general types, the elongated and the short. The elongated stems, which are so well illustrated by the Solomon's seal and May-apple (Fig. 27), UNDERGROUND STEMS 37 bear roots at regular intervals and show well-defined leaf scars at the nodes. Some grasses, such as the witch grass, have similar underground stems bearing buds at the nodes. When such grass stems are torn to pieces by the farm implements each ^J \^ <'io. 29. — Potato showing the tulier type of ste Fig. 30. — Stem or trunk of the birch showing the pecuHar markings of the bark. bud is capable of growing into a new plant. Such stems are called root stocls or rhizomes. Shortened stems have very short internodes and are generally designated as bulbs (Pig. 28) and tubers (Fig. 29). The bulbs are very short stems covered with scales which are reallv modified leaves. These scales may be 38 STEMS AND BUDS very prominent^ as in the easo of the liyacintli or onion, or they may be small and on a very short, thick, fleshy stem, as in the case of the Indian turnip. This last type is known as a conn. Bulbs or bulblets are sometimes borne on the stem above ground; they are nothing more nor less than modified buds. Sometimes the underground stems become very thick and fleshy and are known as tubers. The common white or Irish potato is an excellent example of the tuber. The so-called " eyes " are buds and indicate the nodes of the stem. True tubers, such as the Irish potato, are fleshy stems and are entirely different from the fleshy roots of such plants as the s\veet potato and the dahlia. Two Chief Uses of Stems. — As previously stated, stems con- nect the roots with the leaves and support the latter in the air and light, but some plants, such as the cactus, have leaves that are poorly developed and of little importance. The stems of these so-called " leafless " plants are green and serve the same function as leaves. (Page 47.) The stems of many other plants are also green and perform the duties of lea^'es for a part or for the entire life of the plants. The young twigs are usually green and have stomata (Chapter IV), the same as leaves. How- ever, these stomata soon lose their original character, and de- velop into lenticles. (Chapter VIII. ) The lenticles are the little specks which are so readily recognized on the smaller twigs. (Figs. 20, 21 and 30.) They will be referred to again. Stems also serve for the passage of the water and food sub- stances from one part of the plant to another. (Chapter VIII.) These are the primary functions of stems, but they also serve many other purposes. In the cacti and other plants living in very dry regions they serve for the accumulation of considerable quantities of water. Floating plants frequently have large chambers filled with air which increases their buoyancy. Many stems, such as tubers, serve for the accumulation of food sub- THE ART OF BUDDING AND GRAFTING 39 stances for future use. Mau has taken advantage of this fact and uses potatoes, onions and many other fleshy stems for food. But one of the most important of the secondary functions of the stem is reproduction This is accomplished by under- ground stems, by the branching and the breaking-up of the root stocks, and by the budding or formation of bulblets in the bulb types. Many plants, lilies and hyacinths, have practically lost their pov^^er to produce seeds and depend entirely upon this method of reproduction. Irish potatoes are very generally grown from tubers, but they ^vill occasionally produce seeds, and the vv^ild potatoes of South America produce seeds very freely. The growing of bulbs of ornamental plants is a leading industry in many parts of the world. Holland is one of the greatest of the bulb-producing countries of the world. Many aerial stems reproduce by runners and offsets and we depend largely upon this method of reproduction to secure plants for agricultural purposes. This is the regular method of propagating strawberry plants. Branches of many plants when set in the soil will produce roots and grow rapidly, and in nature broken branches of willows and many other plants catch in the soil or become partially covered and grow. We have taken advantage of this tendency and propagate many useful plants from cuttings. The art of budding and grafting is based on this tendency of cuttings to grow under favorable conditions. Budding consists in setting the buds of one plant within the bark of another plant, and is generally used in propagating peaches, clierries and sim- ilar fruits. Grafting consists in setting a part of a living twig with its buds from one tree into the branch of another and is very generally used in propagating apples and similar fruits. The structure of stems, their methods of gi-owth and the movements of the plant juices through them will be taken up in a later chapter. In the first chapter we learned that plants are made up of 40 STEMS AND BUDS but three primary organs, roots, stems aud leaves, and that the other so-called organs with which we are so familiar are moditi- catious of these three. We have already studied the roots and the stems, but before taking up the study of the leaves let us con- sider the buds which are undeveloped shoots or stems. Fig. 31. — A newly opened leaf bud of the maple and the same bud dissected to show graduation from scale to leaf. A leaf bud consists of a very short, undeveloped stem bearing a compact mass of minute leaves. (Figs. 20, 21 and 31.) This stem will elongate and the leaves grow to full size. It is then known as a stem or shoot with its leaves. Flower buds are those which develop into flowers, but we will learn later that flowers are made up of modified leaves on short stems and therefore, it is not necessary to change our definition of a bud. (Chapter V.) Location and Structure of Buds. — Buds are borne in the axils, that is just above the point of union of the leaf to the stem. In our northern climates they are produced a year in advance of their development into shoots or fiowers and remain over winter in a dormant or resting condition. In temperate climates the buds are frequently spoken of as scaly buds becanse the lower or outside leaves are modified as scales and serve to LOCATION AND STRUCTURE OF BUDS 41 protect the true leaves and flowers within. These scales never develop into true leaves. The examination of the buds of many of our plants in the spring will show a gradual graduation from scales on the outside to well-formed leaves on the inside. (Fig. 13.) These outside scales are frequently covered with masses of plant hairs (trichomes) or with wax or have the appearance of being varnished. These structures serve as a protection against the entrance of water which would cause great damage, espe- cially during the winter season. Many of the plants of warm climates and some of the plants of temperate climates have naked or nearly naked buds ; that is, buds that have very little or no protection from the climatic conditions. Buds are also classified with reference to their location on the stem. Those at the tip are apical or terminal, while those on the sides are lateral. Lateral buds may be opposite or alter- nate. When lateral buds are directly in the angle formed by the stem and leaf they are axillary, but when to one side or above they are called accessory. Buds borne on other parts of the stem, on the roots and on the leaves are known as adventitious ; they are of the greatest importance in the propagation of plants by cuttings. A plant cannot produce food for the growth of all of its leaf buds into shoots and, therefore, many buds perish, but some of them remain dormant and many later develop into the well- known sucker or water shoots. Such growths are very common on trees that have been over-pruned, or broken by storms. If it were possible for all the buds to grow, all our trees would as- sume the characters of very dense hedge plants. The tendency of some plants, such as the privet and osage-orange, to produce a very large number of shoots increases their value as hedge plants and ornamentals. The growth of shoots from the buds may be definite or in- definite. The definite annual growths are those in which the 42 STEMS AND BUDS shoots increase in length for a few weeks only and the remainder of the season is used for matnring the wood and bnds. Such growths are not likely to winter-kill, and the growths of succes- sive years can be readily traced by the bud scars on the stem. The shoots of other plants grow throughout the entire season and until checked by the cold weather ; they are known as iridefinite growths, and are likely to suffer from winter injury. The roses, lilacs, sumac and ailanthus or tree-of-heaven are excellent ex- amples of this type of gTowi;h. Underground stems produce buds at the nodes in the same manner as the stems above ground. The so-called " eyes " of the potatoes are buds which give rise to shoots. The bulbs of many plants, although usually described as stems, are, in reality, buds. EXERCISES WITH STEMS AND BUDS 1. Study of Woody Twigs. — Cut a branch from a maple, linden, horse chestnut or other dicotyledonous tree and note the nodes and internodes of the newest growth as marked by buds and scales ; trace as many seasons of growth as possible, beginning with the tip of the twig. Examine the bark with a hand lens and note leaf scars, lenticles and other peculiarities. 2. Monocotyledonous Stems. — Examine a corn stalk, grass stem, grain straw and other monocotyledonous stems and compare with a woody stem studied in previous exercise. ■'>. Cross-section of Herbaceous Stem. — Cut through a Begonia stem (dicotyledonous), examine with a hand lens and note (a) the central mass or pith surroiuided by (b) a circle of wedge-shaped areas which are fibro- vascular bundles of wood, and which are separated from each other by material like the pith and known as medulkiry rays. Outside the fibro- vascular bundles is another zone which is in turn surrounded by the epidermis or harJ: covering. 4. Layers of Bark. — ^Take the last season's growth of a lilac, horse- chestnut or maple. Gently scrape oil the outer brown bark, the inner green bark and the fibrous bark and examine with a hand lens and note, (a) the outer bro\\TX baik layer, (b) the second or dark green layer of new bark and (c) the third layer of tough fibrous bark or bast. .'>. Cross-section of Woody Twigs. — Cut through a woody twig of oak or basswoful and note (a) tlie central pith surrounded bj^ (b) the EXERCISES WITH STEMS AND BUDS 43 wedge-sliaped fibro- vascular huiulles separated l)y {(■) the radiating medullary rays and {d) the concentric circles or annular rings. 0. The Parts in Large Timber. — Examijie the cut end of a large stem or tree trunk and note the same points as in the preceding exercise. Examine the enda of sawed timber and determine the above parts. Trace them in the long section of the timber. 7. Rise of Sap in Stems. — Stand tlie freshly cut stems of Begonia, liorse-chestnut and other plants in water colored with eosin or red ink for 30 minutes, one hour, and for 24 hours. Cut off small pieces, beginning at the base and examine with a hand lens. Note the part through whicii the colored fluid rises and tlie height to which it has risen. 8. Persistent Upward Tendency of Stems. — Take an upright, pot- ted plant and place in a horizontal position (pot and all). Make a dia- gram to denote the relative position of the parts and examine again at the end of 24 and 4S hours. 9. Datndelion Stem and Buds. — Examine the short stem of the dan- delion or similar plant. Count the number of Imds you can find near tlie surface of the soil. Does the number vary with the size and age of the plant? Split the entire plant lengthwise and try to determine point of union between stem and root. 10. Examine the under-ground stem of Solomon's seal, May-apple, Johnson grass or similar plants and compare with an aerial stem. 11. Examine the bulbs of crocus, tulip, gladiolus, Indian turnip, onion, etc., and note their general character. Cut them open lengthwise and note the short stems and scale-like leaves. 12. Examine a potato tuber and note its general character. Note the arrangement of the eyes or buds. Compare with the fleshy root of a sweet potato. Cut through it and note the fibro-vascular bundles just beneath the epidermis or peeling. 13. Buds of Twigs. — Examine the stems of lilac, horse-chestnut, hickory and maple. Note number, arrangement and relative sizes of the buds on the different stems and on the same stem. 14. Structure of Buds. — Take the large buds of the lilac, horse- chestnut, hickory, etc., and carefully dissect by successively removing the scales and inner parts. Note the gradual transition from scales to leaves. Note the short, conical, undevelo[)ed stem to which tliey are attached. Compare the bud to a scaly bulb. (This study is most satisfactory if conducted in the early spring when the buds are swollen. In winter the stems should stand in water a few days before the study.) 15. Opening of Buds. — Cut a few of tlie newest and most vigorous shoots from a lilac in winter or early in the spring before tlie buds open and place in water in a warm room. Examine from day to day and note the opening of the buds and growth of new shoots. 44 STEMS AND BUDS QUESTIONS 1. What is the stem? 2. What are nodes? Internodes? 3. Name and explain the types of stems. 4. Describe a cross-section of each. 5. Describe the outside coverings of a stem. 6. What are tlie annual rings ? 7. What are the differences between herbaceous and woody stems? 8. What do you understand by acaulescent? Excurrent? Decumbent? Prostrate ? 9. Explain the methods by which plants climb. 10. How can you distinguisli underground stems from roots? 11. Describe a rhizome. A bulb. A tuber. Give examples of each. 12 What are len tides? 13. What are the various functions of] stems? 14. Read and give a report of the flower industry of Holland. 15. Read and give a report of the history of the potato. 10. Explain the natural methods of plant propagation by means of stems. 17. What are the artificial methods of plant reproduction by stems? 18. Compare a corn stalk with the stem of a woody plant. 19. What are medullary rays? 20. Through what part of the stem does water rise? How demonstrated? 21. When you examine the cut end of a large woody stem what do you see ? 22. What occurs when planta are exposed so as to receive the sun on one side only? 23. What is the general direction of stem growth as compared with root growth ? 24. \Miere do you find the fibro-vascular bundles in the tuber of the Irish potato? 25. Compare the tuber of the Irish potato with the root of the sweet potato. 2G. What is a bud? 27. What is a flower bud? 28. Where are buds borne? 29. When are buds produced ? 30. What do you understand by apical, lateral, opposite, alternate, axillary, accessory and adventitious buds? 31. Do all the leaf buds grow into shoots? Whyl 32. What do you mean by definite and indefinite growths? 33. What are the eyes of the potato tuber? CHAPTER IV LEAVES The leaves of a plant are always borne on the stem and have the same relative position as the buds. (Figs. 20 and 21. ) They are the expanded parts of the plant and have a definite rela- tionship to the air and simlight. Green plants must have an expanded surface (usually the foliage) into which the gaseous elements (Chapter X) of the air may pass. These gaseous elements are as necessary for the growth of the plant as are the raw food materials of the soil. These expanded parts contain chlorophyll or the green coloring material which is necessary for the formation of true food sub- stances from the elements and compounds obtained from the water, soil and air. Relation to Light. — If you stand under a tree and look upwards, you will note that the leaves are on or near the tips of the twigs and thus form a canopy or tent with the trunk and branches as the supporting framework. If you place yourself in such a position as to look down upon a small tree or other plant or at a vine (Fig. 32), climbing over a wall you will be surprised to note how very little the leaves shade one another, and that all have very nearly the same light and air exposure. The leaves of many plants, especially the legumes, are also raised and lowered to some extent throughout the day in such a manner as to receive the sunlight to the best advantage. The leaves are the factories in which the raw food sub- stances are transformed into true food substances for the growth of the plant. The water and these various raw or crude food substances which may be dissolved in it are taken from the soil 45 46 LEAVES and carried to the leaves where the most of the water is trans- pired into the air. (Page 114.) The leaves take carbon dioxide gas (CO2) from the air and as a result of the action of the sun- light on the green coloring matter (chlorophyll) these sub- stances are transformed into starch. This process is known as Fig. 32. — Ivy leaves on a wall showing the arrangement with very little overlapping. photosynthesis (Page 11 T)), which is the most remarkable process in all nature. It is the most important process in plant gi'owth, and without plant life there could be no animal life. Sunlight and Chlorophyll. — The formation of the complex food substances or compounds from the crude materials of the soil and air is accomplished in green plants only and, there- SUNLIGHT AND CHLOROPHYLL 47 fore, all animals and all plants that do not contain chlorophyll are dependent either directly or indirectly upon these green plants for their food supply. Different kinds of plants require varying amounts of light and, therefore, we find some plants growing in the direct sunlight, while others are usually found in the shade and will not thrive in the intense sunlight. We also notice that the arrangement of tlie foliage on the plant, and its Fig. 33.— Self-pruned twigs of the poplar showing the cleavage planes. position during different hours of the day and on cloudy and clear days, are such as to relieve the sunlight in proportions more or less suitable for its own work. Plants gTowing in the desert, or other dry places, may be " leafless " or have the leaves greatly reduced, but the stems of such plants contain the chlorophyll and serve as foliage. Plants may produce more foliage than is necessary for their normal growth. Rueh plants may drop in- dividual leaves or even large shoots during the growing season by a process of self-pruning. These leaves and shoots are not 48 LEAVES broken off but " grow off " by the formation of definite cleav- age planes as in the shedding of leaves for winter. This self- pruning process is very common among willows, poplars, cotton- woods and many other trees. (Fig. 33.) Parts of Leaves. — A simple, typical leaf (Fig. 34) has a blade or lamella supported by a framework composed of libs Fig. 34. — Simple net-veined leaf. Fig. 35. — Simple parallel-veined leaf. and veins. The principal rib is known as the midrib and is a continuation of the leaf stem or petiole. Leaves which do not have petioles are sessile. These ribs and veins are continuations of the woody bundles found in the stems and serve not only to support the leaf but as channels through which the water and raw food materials pass to the leaf, and through which more com- plex food substances' pass to other parts of the plant. Minute structures, known as stipules, frequently are found at the bases of the petioles. They are extremely variable in form and character. Sometimes they are leaf-like and may fall soon after the unfolding of the leaves as in the willows ; sometimes they are TYPES OF LEAVES 49 attached aloi;g the margin of the petioles as in the clovers; sometimes they are developed as sheaths enclosing the stem as in the grasses and grains ; and sometimesi they enclose the young leaves as in the tulip tree. Types of Leaves, — Leaves which have one prominent mid- 1. — Palniately veined leaf Fig. 37. — Palmately veined leaf. rib running from base to apex, and giving rise to numerous side branches with smaller veinations between them are said to be net-veined (Fig. 34), while leaves which have a number of equally prominent veins running from base to tip are said to be parallel-veined. (Fig. 35.) Most dicotyledonous plants have net-veined leaves, while most monocotyledonous plants have parallel-veined leaves. Leaves which have three, five or more prominent ribs or veins arising from a common point are said to be palmate-net-veined or radiate-net-veined (Figs. 36 and 37), while those that have numerous veins arising from a main mid-rib are said to be pinnate-net-veined or feather-net- veined. (Fig. 34.) 50 LEAVES Compound Leaves. — Leaves which are composed of two or more leatiets arising from a single petiole are said to be com- pound and are described as iMlmale- or radiate-compound (Fig, 38), or as pinnate- or feather-compound. (Fig. 39.) The size, form, arrangement and various other modifications of the leaves of plants are largely dependent upon the environmental factoi'S, Fig. 38. — Palmately compound leaf. Fig. 39. — Pinnately compound leaf. especially light and moisture. Land plants, growing in very wet surroundings tend to have larger leaves than those growing in dry or arid surroundings. Aquatic plants in running water tend to have long, narrow leaves as compared with plants living in still water. The Leaf Blade. — The veination of the leaves supports a delicate structure (Page 102), within which are numerous air USES OF LEAVES 51 passages with openings (stoniata) to the outside, usually on the lower surface. These passages and openings facilitate the trans- piration of water (Page H-i), and the absorption of gases. (Page 115.) The texture of leaves varies largely with the en- vironment in which they live. The surfaces of leaves are also frequently covered with spines, hairs (trichomes), gland hairs, wax, etc., which serve to protect the plant, prevent excessive transpiration and otherwise facilitate its work. Uses of Leaves. — Leaves are so abundant, and come with such great regularity that we are likely to fail to appreciate their importance in the life of the plant. But these very common- place facts should convince us that they are invaluable to the plant, that they are something more than elements of beauty in the individual plant or in the landscape. We have already learned that the primary function of leaves is to serve as foliage through which the living, growing plant receives gases from the air and energy from the sun and in which the raw food substances are transformed into true foods (photosyn- thesis, Page 115). But the leaves serve many other useful pur- poses which are important in the life history of the plant: (a) they are the organs of transpiration (Page ll-l), by which are given off quantities of water previously absorbed through the roots; (h) they are organs of respiration, although this func- tion is not confined to the leaves; (c) they may serve as bud scales for the protection of the more typical foliage leaves and flowers (Page 40) ; (d) they may develop a bitter gnim and thus serve as a protection against birds and other small animals which feed on the new growths in the early spring; (e) or they may develop as briars or thorns which, no doubt, serve to some extent as a protection against larger animals. Thistles and other plants which are armed with these protective structures will stand unmolested in the stock pasture, even though the food 62 LEAVES supply for the cattle may be very limited. Every good farmer knows the advantage of using sheep or goats for the cleaning of neglected lands of these anued weed pests which most live-- stock will not touch. Leaves also serve for the storage of food and water as in the case of the so-called " century plant," which grows for a number of years and then develops its flowers and seeds at the expense of the food stored in the large fleshy leaves. This is no more wonderful than the common cabbage in which exactly the same thing occurs in a cycle of two years ; the accumula- tion of the food is during the first, and producing the flower and seed during the second year. Man has taken advantage of this tendency of the plant to store its food in the leaves and makes \ise of many such plants as food for himself. Leaves may also serve for the storage of air as in the case of the floating- plants which contain large air-chambers. In some few plants the leaves have undergone modifications, enabling them to serve as insect traps for the capture of insects which die, decay, and furnish a supply of nitrogenous food for the growing plant. The most interesting insect catchers are the sun-dew, Ven\is fly-trap, and the pitcher plants, which you will find described in an encyclopedia, and in many works on botany. Probably the most important function of leaves after photo- synthesis is the formation of flowers and fruits, for as we shall learn later, the flowers are modified leaves. (Page 54.) EXERCISES 1. Collect the followin» forms of leaves: simple net- veined, simple par- allel-veined, simple palmate-veined, compound palmate-veined and com- pound pinnate-veined. Make drawings and label the parts. 2. Collect and make drawings of leaves with and without petioles. 3. Collect leaves showing different types of stipules. QUESTIONS 53 QUESTIONS 1. On wliat part of the plant are tlie leaves boine? 2. Why is it necessary that the leaves should be exj)osed to the air? 3. What are the sources of plant food? 4. Why is it necessary that the plant receive sunlight? 5. Why are animals dependent on plants for food? 6. Are there any other sources from which animals can secure food? 7. What parts of the plant other than the leaves may possess chlor- ophyll? Give examples. 8. Name the parts of a simple leaf. 9. What are the differences between net- and parallel-veined leaves? 10. Wliat are the differences between simple and compound leaves? Give examples of each. 11. What are the functions of the leaves? CHAPTER V THE FLOWER Having studied the three primary parts of the pUant, the root, stem and leaves, we now turn our attention to the most important secondary organ, the flower. The flowers of many plants are objects of beauty, but the great majority of plants bear flowers which are very small and inconspicuous, or which are of such character that they do not attract the attention of the casual observer. Many people are so accustomed to think- ing of flowers as mere objects of beauty that they fail to realize the very great importance of these organs in the life history of the plant. The flowers contain the sexual organs of the plant and are necessary for the production of seeds and fruits. Parts of the Flower. — The flower does not present any new structures, but is a shortened stem bearing circles of leaves, which have been greatly modified in shape and color into parts constituting the flower. Instead of being borne on a long stem, they are now brought together in circles and the shortened stem is known as the receptacle, or torus; the first or outer circle, composed of parts which are usually green and resembling ordinary leaves, is known as the calyx, and each leaf-like part is called a sepal; tlio second circle or series of circles composed of parts which also have some resemblance to leaves but which are usually colored is known as the corolla, and each part is called a petal; the third set of organs consisting of one or more circles is composed of stamens which bear very little resemblance to leaves; the last or central group consist- ing of one or more organs which may be distinct or united is the pistil which also bears very little resemblance to leaves. (Figs. 54 PARTS OF THE FLOWER 55 40 to 44.) The calyx and corolla constitute the floral envelope or perianth while the filamois and pistils are the sexual or essen- tial organs of the phmt. The arrangement of the organs in circles permits the making of diagrams which represent the general plan of a Hower as clearly as a map shows the physical FiQ. 40. — a, cherry blossom; b and c, diagrams showing the arrangement of the parts. FiQ. 41. — a, diagrammatic longitudinal section of apple blossom; b and c, peach bloBSom. and political divisions of the earth. If this diagram is accom- panied by a second diagram made at right angles to the first, the general architecture of the flower is well shown. The sepals and petals being leaf-like in character sometimes grade imperceptibly the one into the other. In some flowers, of which many lilies are examples, the parts of these outer circles 56 THE FLOWER are practically alike in both shape and color; while in other flowers there is no corolla. When the corolla is missing, the calyx may be green, but it is usually of some other color which deceives many observers into believing it to be the corolla. The common hepatica and the wind flower are good examples of flowers with colored calyx and no corolla. When the corolla alone is absent, the flower is described as apetalous {i.e., without petals). Some plants have flowers Fig. 42. — Diagrammatic drawing and cross-section of a lily. Fig. 43. — Diagrammatic longitudinal and cross-sections of a pea blossom. with neither calyx nor corolla, but these incomplete flowers are just as important in the life history of the plant as the very complicated and highly colored flowers of other species. The stamens in most flowers are distinct and have no external resemblance to leaves, but in some flowers the gradual transi- tion from petals to stamens is so apparent as to leave no doubt whatever as to origin, even in the mind of the most casual observer. This is especially well illustrated in the white water lilies. In a state of nature, we sometimes find flowers in which the petals assume stamen character or the stamens tend to FLOWER TYPES 57 become petal-like in ciiaracter. This teiideucy in plants makes it possible for the Horist to develop double flowers from the natural single ones ; the wild rose has but five petals, and numerous stamens, but the double rose has many petals and few or no stamens, they having been transformed into petals, more or less like the other petals. The pistils are more distinct than the stamens but will sometimes assume petal-like characters. The organs of some — S Fig. 44. — a, twig and two clusters of elm blossoms; b and c, diagrammatic longitudinal and cross-sections of a single blossom. flowers are imperfect and of no use to the plant. If all of the stamens or all of the pistils are imperfect the plant cannot produce seeds and, therefore, must be propagated by some method other than by seeds. This will be explained later. (Chapter VI.) Flower Types. — A flower which is composed of the four sets of organs is said to be compleie (Fig. 40), and a flower pos- sessing both stamens and pistils, regardless of the presence or absence of calyx and corolla, is said to be perfect. (Fig. 40.) A flower in which the number of organs in each set is the same or a multiple of the same is symmetrical. (Figs. 42 and 43.) 58 THE FLOWER If all of the organs of each set are the same sizel and shape it is regular, (i'ig. 40.) The opposites of the ahove are: incom- plete, imperfect, unsymmetrical and irregular. The, apple, peach and cherry (Figs. 40 and 41) are complete and perfect; the lily (Figs. 42 and 51) is symmetrical and regular ; the com (Figs. 46 and 48) and castor oil plant are both incomplete and imperfect ; the apple and j)each nnsym- metrical ; the violet and bean (Fig. 47) irregular. Imperfect Flowers. — Some plants bear two kinds of imperfect flowers, those with stamens which are known as staminate flowers, and those with pistils which are known as pistillate flow- ers. In some cases the two sets of flowers are so different in general appearance as to Fig. 45.— Single blossom of rye; a, stamen; o, be rcadilv distinguished while pistil. . "^ m other cases they are very much alike and cannot be distingiiished except by a more care- ful examination. Plants which bear these two kinds of imperfect flowers are said to be monoecious (Figs. 46 and 48), i.e., of one household. The common corn is a good example of a mon- oecious plant, the tassel being composed of staminate flowers while each grain with a single thread of silk is a pistil. Each mature grain of corn is a fniit produced from a single pistil- late flower. Other plants bear the staminate and pistillate flowers on difl"erent individuals and are knovra as dia'cious (i.e., of separate IMPERFECT FLOWERS 59 ? Fig. 46. — Two ears of Indian corn; i.e. the pistillate flower. households). The mulberry, willow and poplar are excellent examples of dioecious plants. The fruits of these plants are always borne on the pistillate plants. 60 THE FLOWER lu the examination of a largo number of plants we will find many interesting modifications of strictly monoecious and di- oecious types. The Indian turnip or Jack-in-the-pulpit (Fig. 49) is usually dioecious, but many plants will be found which are monoecious. Some species of plants, of which the maples are good examples, both bear perfect and imperfect flowers, while individuals are frequently found which do not bear flowers of any kind. 4^^000^ Fig. 47. — LpRume blossom; a and I), the hlossoiu; c, the blossom dissected showing the petals; d, the sepal, stamen and pistil; e, the mature seed pod. Modified Calyx and Corolla — Both the calyx and the cor- olla are frequently modified. The simplest modification is the union or partial union of the sepals or petals or both to form tubes. Flowers in which these unions occur are described as gamo-sepalous and gamo-petaJous (Fig. 50), while those in which there is no union are described as poly-petalous and poly- sepalous. (Figs. 40, 42, 43 and 51.) The petals and sepals may also be modified to form spurs, as in the violet, or in many other ways. The calyx and corolla are borne on the receptacle, but in some cases the corolla appears to be attached to the calyx. We will find these numerous modifications of very great inter- est, and they are of very great importance in the life history of PARTS OF THE STAMENS 61 Fig. 48. — The tassel ur staininate flowers of the Indian corn. the plant. This question will l)o taken u]) more fully on page 80. Parts of the Stamens.— An ordinary stamen (Fig. 40) con- sists of two very distinct parts, the filament or stem, which corresponds to the petiole and midrib of a leaf, and the anther, at the tip, which corresponds to the blade rolled or modified so 62 THE FLOWER as to form small sacs containing- a delicate powder, known as pollen. The stamens also present different forms in the various plants. They are usually borne on the receptacles, but some- times appear to be attached to other parts. They are fre- quently united into groups and in some plants in such a manner as to form a tube enclosing the pistil. The little pollen sacs have differ- ent methods of opening which may be readily seen with the hand lens and which will prove very interesting to the close observer. The pol- len is very important, No two plants have exactly the same kind of pollen. It var- ies in size, shape and struc- ture. The study of the pollen of various flowers under the microscope is very interest- ing. It is carried by wind and water, and sometimes by other means to the pistil, where it undergoes a growth which will be described later. (Chapter VI,) The Pistil.- — There may be one or more pistils. (Fig. 40.) If one, it may represent one or it may represent many united leaves. Where there are two or more pistils, they may be en- tirely separate or they may be partly united. The pistil is com- posed of an ovary or basal part containing the ovules, which are to become seeds; a style, which varies in length in different plants; and a stigma, which is the only part of the plant not Fig. 49. — Indian turnip or Jack-in-t he- pulpit; a, bulb; b, leaf and spathe; c, spathe open to show spadrix and flower near the THE PISTIL 63 covered with an epidermis or skin. The pistils are also subject to many moditications, but are always borne on the receptacle. However, if the other organs originate below the ovary, it is said/ to be superior (as in the peach flower), but if they origin- ate above it, it is said to be inferior (as in the apple blossom). The arrangement of the organs in the flower can be described by three tei-ms: liypogynous (Fig. 4-i), the simplest form, in which the sepals, petals, and stamens arise from below Fig. 50. — Squash blossoms. A gamopetalous flower. the carpels; perigynous (Fig. 40), in which the receptacle is extended into a cup-like structure about the carpels and bearing the sepals, petals and stamens on its rim and frequently more or less united at their bases ; and epigynous, in which this cup envelops the ovary, thus giving the true inferior ovary. The modified leaves of which the pistil is composed are frequently called the carpels, and the point of attachment of the ovules is called the placentae. The placentse may be either central or parietal {i.e., on the sides of the ovary). The num- ber of carpels can usually be determined by cutting a cross sec- tion of the ovary and examining with a hand lens ; the number of carpels being represented by the number of fibrous bundles which correspond to the midribs of the leaves of which the 64 THE FLOWER pistil is composed. The number of carpels does not necessarily correspond with the number of chambers in the ovary. Of course, it will be readily recognized that the ovary eventually becomes the seed case of a dry fruit and that it is also an im- portant factor in the formation of fleshy fruits. Fig. 51. — Lily blossom. A polypetalous flower. Flower Clusters. — The arrangement of flowers on the stem is called the inflorescence. A few of the most common types of inflorescence are as follows: (1) The raceme (Fig. 52) in which a number of flowers are borne along a stem, the lower blooming first. The minute leaf which is usually at the base of each flower is called a bract. (2) The corymb is a raceme in which the pedicels, or little stems, of the lower flowers are elongated so that the flowers are practically on the same level. FLOWER TYPES 65 (3) The umhel (Fig, 5.']) in which the pedicels arise from the same point and are practically the same length. (4) The spike (Figs. 54, 55 and 50) in which flowers are nnmerous, compact and sessile. (5) The head (Figs. 57 and 58), in which the main stem is shortened, giving rise to a cluster of flowers form- ing a more or. less definite sphere. (6) The spadix (Fig. 49) in which the main stem is fleshy and the cluster of flowers en- veloped in a leaf-like structure called a spathe. (7) The catkin in which the minute flowers are more or less compact, and the Fig. 52. — Toad flax blossoms, showing the open development of the blossoms. entire raceme pendant. (8) The cijme which is similar to the raceme, but which difl'ers from all of the preceding by having the apical flowers bloom before the lateral flowers. Finally, there are many special terms which are used for describing other forms of inflorescence, but which we will omit for the present. CLASSIFICATION Flower Types — "Wlien we stop to think about, or try to count and record the many plants with which we are familiar, although we may not know their names, we find that we have a task which is extremely difiicult. But when we realize that we know only a few of the many hundreds of thousands of plants of difi^erent kinds which are distributed over the face of the earth, we understand that we must have some very definite system of classification or grouping by which we will 6 66 THE FLOWER be euabled to locate aud record them and designate those in which we are most interested. This system must be the same throughout the world and for people of all civilized languages. Several systems have been suggested, used and discontinued at various times during the centuries that mankind has studied plants. The one that we now use is known as the natural system and is, no doubt, better than any of the preceding. By this system, we try to group or classify plants by their blood relationships and not upon the superficial resemblances. We readily recognize that apples, pears and quinces are very much alike. The foliage on the trees is almost identical, the flowers have corresponding parts in the same general ar- rangements, and if we cut the fruits we find that they have the same general characters. Peaches, plums and cherries form another well-defined group ; they also have flowers and fruits of the same character. l^ow if we compare one of the two groups with the members of the other we find that the flowers of all are very similar except that in the ovaries and fruits of the two groups they are quite difi'erent. In the first group the ovaries are inferior and the fruit with a five-parted, papery seed chamber, while in the second group, the ovaries are superior and have the one stony seed chamber. If we take the blackberries and the raspberries as repre- senting a third group, we find flowers similar to the preceding but with masses of superior ovaries; and if we take the wild Fig. 53. — Wild carrot blossoms. The umbel type of inflorescence. FLOWER TYPES 67 rose as representing a fourth group, we again find flowers strikingly similar to these groups but with inferior ovaries that never have the development represented by the apple. Fig. 54. — Sedge or spike type of inflorescence. Fio. 55. — Blue grass inflorescence. Now, the very great resemblance in all these gi'oups leads us to place them all in the one family, Rosacece. But in the study of these characters we must make sure that the resemblances are real and not superficial. The fruits of the blackberry and mulberry are very similar in general appear- 68 THE FLOWER aiice, but when we go back to the flower and study them botan- ically, we find that they are qnite different ; the fruit of the former is composed of the many ripened ovaries of a single ^ "^ "^ %""' ii^r V\ ^ '%. m\ \*> ^%^ ^ m 1 Fig. 56. — Rye inflorescence. flower, while the fruit of the latter is composed of the ripened ovaries of a number of small flowers. On the other hand, the potato, tomato, pepper and tobacco FLOWER TYPES 69 may appear quite ditfereut, but an examination of the flowers shows them to be very similar and belonging to one family {Solenacew). The flowers of the potato, tomato and pepper are very similar ; the flower of the tobacco is somewhat difi^erent, Fig. 57.— Sunflower head. Composite type of inflorescence. but has the same general characters ; the cultivated potato has almost the power of producing fruit, but when the fruit is pro- duced it is very similar to a small tomato ; the fruit of the tomato is fleshy; the fruit of the pepper very similar but tending to become leathery; the fruit of the tobacco is of the same char- acter but tending to become papery in character. 70 THE FLOWER The Natural Classification endeavors to grmip plants in accordance with trne botanical resemblances, and these groups are combined into larger, nntil we have the entire plant king- dom in four large groups. Thus far we have studied flowering plants only, but the plant kingdom includes many plants which do not produce flowers or seeds. The principal groups of the plant kingdom may be represented by the followig outline : A. Cryptogams (Seedless plants) 1. Thallophytes 2. Bryophyte 3. Pteridophytt a. Alg« — mostly water plants. h. Fungi — plants witliout clilorophyll; moulds, muslirooms, etc. a. HepaticfE — ■ Liver - worts. b. Musci — ^INIosses. a. Ferns and related plants. B. Phanerogams (Seed plants) 4. Spermatophytes a. Gymnosperms — cone- bearing plants ; pines, cedars, etc. 6. Angiosperms — true flowering plants. For the present we will not study the Cryptogams or the Gymnosperms, but will continue our studies on the Angiosperms or true flowering plants. We have already learned that this last group is sub-divided into monocotyledonous and dicotyledon- ous plants, and that in the former the embryo has but one cotyledon, while in the latter it has two. When we do not have the seed, or when it is too small for the determination of this point with ease, the classification may be determined by the following characteristics of the mature plant : The monocotyle- donous plants usually have leaves with parallel veins and stems EXERCISES WITH FLOWERS 71 with irregular arrangement of fibro-vascular bundles {endogen- ous) ; the dicotyledonous plants usually have leaves with net veins, and stems with the fibro-vascular bundles definitely ar- ranged to form a circle {exogenous). Both groups are sub-divided into orders, and these orders into families, these families into genera, and these genera into species. The generic and specific names constitute the scientific or Latin name of the plant. The classification and naming is the same in all civilized languages. The committing to memory of classifications and scientific names is wasted time and useless, unless we understand the relationship of plants and the basis for their groupings. However, a careful study of plants will enable the thorough and closely observing pupil to classify many plants to their families and even to their genera with- out the use of a manual. Students who are interested in the classification of plants should secure and use a manual suited to the locality in which they live. Fio. 58. — Dandelion head. Composite type of inflorescence. EXERCISES WITH FLOWERS 1. Plant Studies. — The study should be associated witli the plant as a whole, provided time and material will permit. The following points should be determined if possible: (1) Is the plant monocotyledonous or dicotyledonous? (2) Is it an herb, shrub, or tree? (3) Under what conditions did it grow? (4) Describe in brief the root, stem and leaf. (5) Is the flower perfect or imperfect? Is the flower complete or incomplete? Is the flower regular or irregular? Is the flower symmetrical or unsymmetrical ? 72 THE FLOWER (6) If imperfect, is it monoecious or difficious? (7) What is the type of inflorescence? (8) Is the flower apetalous or complete? (9) Is the flower poly- or gamo-sepalous? ( 10 ) Is the flower poly- or gamo-petalous ? (11) Is the ovary superior or inferior? ( 12 ) How many sepals, petals, stamens and pistils ? (13) To what are the different sets of organs attached? (14) If unsymmetrical, describe the parts. (15) Describe the stamens. How do they open? (IC) Describe the pistil or pistils. What type of placenta? How many ovules (estimated by cross and long sections) ? (17) If a single pistil, how many carpels and cliambers? 2. Plant Description. — Having determined the preceding points a com- plete description of the plant and flower should be written. The pupil is now ready to use a manual for the determination of the family, genus and species. The family characters should be carefully noted and when an- other plant of the same family is studied, the pupil should try to determine the family without the use of a manual. 3. Careful dravi^ings and diagrams should be made of all plants and flowers studied. The following types are suggested for these exercises: Monocofyledonous Lily Tulip Lily of the Valley Amarillus Indian turnip Wheat Oats Com Rose Apple or pear Peach, plum, cherry Blackberry Pea or bean Bloodroot Mustard Buttercup Dicotyledonous Potato or tomato Sunflower or daisy Dandelion Morning glory Melon or gourd Maple Elm Oak Willow QUESTIONS 1. What are the parts of the flower? 2. What constitutes the floral envelope? 3. Wliat constitutes the essential organs? QUESTIONS 73 4. What do you understand by complete, perfect, symmetrical and regular flowers? Give examples of each. 5. What is meant by apetalous, gamo-petalous and poly-petalous? 6. What is meant by monoecious and dioecious"? 7. What is tiie difference between superior and inferior ovaries? Give examples of each. 8. Define carpel, placenta. 9. Give the different forms of inflorescence and examples of each. CHAPTER VI REPRODUCTION Reproduction Without Seed. — We have already referred to some of the methods of reproduction in plants. We have learned that a bud is an undeveloped stem with its undeveloped leaves ; and that the cuttings of many plants when placed in moist soil or in water will grow readily ; that is, the buds expand, a root system is developed and a new plant possessing a complete set of organs like the parent is formed. In nature many plants, such as the willow, shed twigs which catch in the soil and grow. This growing of twigs explains the rapidity with which willows come into existence along water courses. Many grasses and other troublesome plants increase in number as a result of having the underground stems torn in pieces by farming tools, thus per- mitting each bud to form a new plant. We know that this power of buds to grow makes it possible to perpetuate many valuable varieties by cuttings, budding, and grafting. These methods are the common practices of florists, nurserymen, orchardists and others who wish to produce large numbers of plants of def- inite varieties. Many plants are grown almost exclusively from the tubers or bulbs which we now recognize as forms of stems (Chapter IV), and many of these plants have partly or entirely lost their power to produce seeds. Plants which have lost this power to produce seeds must be grown entirely from bulbs, or cuttings, or by budding or grafting. We know that, although roots do not generally produce buds, many plants are propagated by shoots developed from adventitious buds formed on the roots. The sweet potato 74 THE TRANSFER OF THE POLLEN 75 is a notable example of a root producing buds and young plants. And linally we know that even the leaves of some plants have the power to produce buds which will grow into plants. But this is not so strange as it may first appear, when we stop to consider that the ovules which develop into seeds are a part of the pistil which is a modified leaf. It is very evident that the preceding methods of reproduction by buds is very rapid and that a large number of new individuals like the parents can be produced in a very short time. It is known as the asexual or non-sexual method. By Flowers and Seeds. — However, the most important, the most complicated, and the highest method of reproduction is by means of seeds which are the result of the sexual activ- ities of the plant. In all the preceding methods of reproduction, each young plant has but one parent. But in reproduction by means of seeds each plant, with a few exceptions (Chapter V), has two parents. The stamens may be considered the male organs and the pistils the female organs, and the process of seed production may be briefly described as follows : Within the anthers are borne great numbers of pollen (Fig. 59) grains which are readily recognized as the powder which is so abun- dant in the large lilies and many other flowers. This pollen must be transferred to the stigma of the pistil of the same or another flower. (Fig. 60.) You will recall that the stigma is the only part of the plant that is without an epidermal cov- ering. (Page 62.) The transfer of the pollen is sometimes accomplished by some of the many insect visitors that are attracted by the honey or odor of the flower, or by humming birds, or in some cases by the wind. The transfer of the pollen is called pollination, and should not be confused with fertilization. Each pollen grain is a single cell which undergoes a growth resulting in the foiTnation of a long, ddicate tube which grows downward 76 REPRODUCTION through the style and eventually reaches the ovule. Tlie tube enters the ovule usually through the micropylo (Chapter 1), which persists and is plainly visible in many mature seeds. In the meantime, interesting changes are going on within the small ovule, which results in the formation of a minute chamber knowai as the embryo sac. (Fig. 01 a.) This sac contains eight minute cells, one of which is known as the ovum or ccjg. Fig. 59. — Types of pollen grain. The tip of the pollen tube finally reaches this egg cell and a certain nucleus from the tube unites with the nucleus of the egg. This is the process of true fertilization, and this fer- tilized Ggg now develops into an embryo or young plant (Fig. 01 h) surrounded by a supply of rich food for its future nour- ishment. This embryo, together with its food supply and cover- ings, constitutes the seed. (Chapter V.) The parts involved in this process are so small that it is impossible to see them without using a compound microscope, and the study of this delicate and complicated process must necessarily be reserved for the more advanced students of botany. 1^0 two plants in nature are ever exactly alike and, there- fore, if the) pollen of one plant falls on the pistil of a slightly DIFFERENCES IN STRUCTURES OF SEEDS 77 different plant of the same or a closely related species or variety, the new plants shonld possess some characters of both parents, This gives a basis for work in the production of new varieties of plants. (Chapter XV.) Differences in Structures of Seeds. — There are some facts concerning the structure of the seed which we have already learned, but which we should now recall in the light of these new facts. (Chapter VIL) The young plant or embryo consists of a very short. stem on one end of which is a root tip ; and on the other end a plumule, or bud, and one or two cotyledons or primary leaves. It is a com- plete plant possessing the three essential parts: root, stem, and leaf. We will recall that the seeds of corn and castor oil plants contained embryos surrounded by an abund- ant food supply for their nourishment dur- ing the period of germination and before they had become firmly established as inde- pendent plants. We will also recall that in the bean we found a much larger embryo without the surrounding food supply. In this case the food for the early growth of the young plant was in the cotyledons. The seeds of corn and castor oil plant matured very early when the embryos were small, but with a good supply of stored food for the growth of the embryo during germination. The seed of the bean matured much later, the embryo having ab- sorbed the surrounding food supply and stored it in the coty- ledons previous to maturity. In the corn, the single cotyledon is an organ which serves for the absorption of the food supply; in the castor oil plant the cotyledons serve first as organs of absorption and later as the primary leaves; in the bean they serve for the storage of the food supply and as primary leaves. Fig. 60. — Diagram- matic longitudinal sec- tion of ovary showing developing ovules. 78 REPRODUCTION The examination of the seed of a large number of differ- ent kinds of plants will show great variation in the relative sizes of the embryos and the amount of the food supply, and will suggest manv germination tests and growth experiments. Fio. 61. — a, diagrammatic drawing of stamen and pistil showing longitudinal section of ovule. The pollen tube is entering through the micropyle; b, longitudinal diasrammatic sec- tion of ovule showing the formation of the embryo. Advantages of the Seed Method. — It is very evident that sexual reproduction is higher an i more complicated than non- sexual reproduction, but let us see if it is of any advantage. It is necessarily much slower than reprod.uction by buds, but the INSECT POLLINATION 79 dry seeds of a plant can undoubtedly resist greater extremes and longer duration of heat, cold and drouth than buds and can be carried to much greater distances by natural means and by man. Many believe that sexual reproduction gives the plants much more vigor than non-sexual reproduction. This belief seems to be supported by tlie fact that when some varieties of plants are grown continuously from cuttings, tubers or bulbs, they tend to lose their original varietal characters and vital- ity. Sexual reproduction, owing to the fact that the two parents are never exactly the same, tends to cause variations in plants, and results in new varieties. This tendency to pro- duce variations is greatly increased by cross breeding different varieties and has given rise to some of our most valuable fruits, vegetables and oraajnentals. (Page 148.) The transfer of the pollen from the stamens to the stigma is knoAvn as pollination and should not be confused with fertilization. (Page 76.). Pollen may be carried by the wind, and some of our most valuable plants depend entirely upon the wind for pollination. The corn and other grains and grasses belong to this class. The tassel of the corn is a mass of small staminate flowers, while each thread of the silk represents a pistil with a single grain of corn for its ovary. During the blooming season there is a rain of pollen grains, some of which fall upon the silk. Of course, this is in a sense very wasteful for the number of pollen grains which are lost is infinitely greater than the number which fall upon the silk {i. e., pistils). Insect Pollination. — The great majority of our flowering plants are pollinated through the agency of insects, which visit the flower primarily to collect the nectar and pollen. Many insects use the nectar immediately for food, but the bees take it into their bodies where it undergoes chemical changes by which it is transformed into honey and then stored up for future use. Many insects are doubtless attracted by the odors of flowers and some few may be attracted by the color, although 80 REPRODUCTION we should remember that it is extremely doubtful if insects cah distinguish shape, size or color for any considerable distance. Interesting modifications of their parts are found in many flowers. These facilitate pollination by means of insects, and some flowers are so specialized that certain insects are neces- sary for this work. Among the simplest of these modifications is the long tubular corolla of the morning glories and honey- suckles which make it necessary that their visitors have long beaks or mouth parts by which they can reach the nectar glands at the bottom. The tubular corolla of the red clover is such that it is imperfectly pollinated except by the bumble bee and, therefore, it is practically impossible to grow red clover seed without these insects. The barberry, and some other plants, have stamens of such character that when touched by the in- sect they serve as springs, striking the anthers against its body. The milkweed and other plants are so constructed that masses of pollen may cling to the body of the insect and be carried from flower to flower, losing some pollen with each visit. Beans, peas, and similar flowers have peculiarly shaped corollas which conceal the essential organs, but when the insect settles upon them these parts are exposed and the lower surface of the body brought in direct contact with them. A thorough discussion of the devices for facilitating the pollination by means of insect visitors would require a large volume and then be incomplete, but it is a subject in which any close observer can learn some- thing previously unknown, something not in the books. Cross Pollination. — It will be readily seen that sexual pollination is usually accomplished by the pollen of one flower on the stigma of another flower of the same or a different plant. This is known as cross pollitiation and, of course, results in cross fertilization which, as previously stated, is believed, in many cases, to give increased vigor to the new generation of plants. If this is true, we are certainly justified in expecting to find some modifications in nature which prevent self-pollifir DICECIOUS PLANTS 81 ation. If we examine Hewers carefully we will find some in whicli the stamens and pistils mature at different times and, therefore, it is impossible for the flower to be pollinated by its own pollen. Of course, the flowers do not open at the same time and pollen of some flowers will mature at just the right time to be transferred to, and grown on, the stigma of others. Sometimes the flowers will be pollinated from other flowers of the same plant and sometimes by flowers of different plants. In some plants we can see the effects of this cross pollination in the seeds, as in the case where corn of one color has been pollinated by com of another, resulting in the speckled or mixed ears. But in most plants we do not see the results of cross pollination until we grow the new plants. Cross pollination is accomplished in various ways. Some plants have two kinds of tubular flowers, some with short stamens and long pistils, and others long stamens and short pistils. The insect visiting the first flower gets pollen on the front part of its body; visiting the latter it leaves some of the pollen on the short pistil and gets a load of pollen on the back part of its body. Therefore, it is practically impossible for the flower to be pollinated with its own pollen. Some plants, especially cultivated varieties, have impotent pollen and, therefore, cannot be pollinated with their own pollen or with pollen from plants of the same variety. Many apple, pear and plum growers mix their varietiesi in the orchard so as to insure pollination and thus get the stimulating effect of fertilization and secure a richer harvest. In some cases, growers may even set a few trees of an inferior variety in order to secure satisfactory cross pollination of the desirable varieties. In some plants, such as the common banana, the pollen is useless and the plants no longer produce seeds. Dioecious plants (Chapter V) are necessarily cross pollin- ated, and many savage and half-civilized races learned, many centuries ago, the necessity of growing the staminate as well 6 82 REPRODUCTION as the pistillate trees, although they had no explanation for this phenomenon of nature. Self-Pollination, — However, the flowers of some plants are very generally self-pollinated. Wheat belongs to this group or class. Buds That Never Open. — The buds of some flowers never open, making cross pollination impossible. Such flowers are called cleistogamous. Some species of violets produce incon- spicuous cleistogamous buds under the leaf -mold, these buds pro- ducing abundant seeds, while the showy^ flowers of these species are usually sterile. EXERCISES IN POLLINATION 1. Carriers of Pollen. — Observe flowers and note the insects which visit them. Are the different species of flowers visited by the same species of insects? Do the insects exercise a choice in visiting flowers? 2. Examine pollen of a number of flowers under the microscope. Make drawings. .3. Pollen Grovi^th in Sugar Solution.— ^lake a solution by boiling one part of sugar in, ten of water. Put a spoonful into each of several watch glasses. Mix the pollen of several flowers into them and keep cov- ered. Examine a drop of the fluid with pollen under the miscroscope from time to time and note the germination. QUESTIONS 1. How* do you account for the rapid increase in numbers of willows and similar plants along water courses? 2. Can other plants be produced in a similar manner? 3. How do w^e make! use of this power of reproduction in the grow- ing plant? 4. How are many grasses and other pests frequently propagated? 5. Give a list of plants that grow from bulbs. 6. Give a list of plants that grow from tubers. 7. Give a list of plants that are seldom or never grown from seeds. How are they grown ? 8. Do roots produce buda? Give some exceptions. 9. Explain pollination. 10. Explain fertilization. 11. Explain cross pollination. 12. Explain self-pollination. 13. Explain cleistogamous seed production. CHAPTER VII FRUITS AND SEEDS We make use of plants in a great many ways, but tlie most important way is as food for the sustenance of life of man and beast. Among the most important parts of the plants used for this purpose are the seeds and fruits. However, these terms {fruit and seed) are very indefinite and should be used with care. Fruits and vegetables are frequently confused; the to- mato is usually spoken of as a vegetable, although the edible part does not differ materially from many true berry fruits. Botanically, a fruit is the ripened ovary, or the ripened ovary ivith such other parts as may he united to it. However, some fruits, such as the banana and the navel orange, have lost the power to produce seeds and the fruit consists of only the ovary. They are known as seedless fruits, and these plants must be propagated by some of the non-sexual methods previously re- ferred to. (Chapter VI.) Although we usually think of fruits as being fleshy structures, the cotton boll, a gourd, a pepper pod, or a bean pod are fruits as truly as is the peach or apple. The seed is the mature ovule with its enclosed embryo, or as wo may have learned, the embryo ivith food supply and coverings. The final result of plant energy is the production of its kind and the distributing of its offsprings as far as possible. Each species of plant, if uncontrolled by climate, water, soil, animals and other plants would eventually tend to occupy the entire earth. But many plants cannot spread beyond a certain limit, because of the extremes of the climate; others are checked for want of suitable soil ; others by bodies of water or desert plains ; and still others by c(miing into competition with other plants which are stronger and crowd them out. Man has taken advan- 83 84 FRUITS AND SEEDS tagc of this tendency of plants to reproduce themselves and to vary their characters, and has selected those which are the best suited to his purposes, and has protected and cultivated them. By his intelligent management he has increased their value to himself. (Chapter XV.) For convenience we will classify fruits as follows : Fleshy. Dry. Drupe . . . . Pome Berry Accessory Dehiscent . Indehiscent. f Simple drupe Aggregate Multiple I Pod or capsule I Leffiinie f Achens I C'aryopsisi I Samara or key Nut The drupe or stone fruit has the seed surrounded by a strong, or hard, stony growth (endocarp) which is, in turn, surrounded by a fleshy growth (exocarp). The stony and fleshy growths constitute the ovary. The peach (Fig. ()2), plum and cherry are of this type, and each fiiiit is a single or simple ovary derivoKl from a single flower. (Page 55.) There are several modifications of the simple drupe which are given special names, but the differences are superficial. They are: (a) The aggregate fruit which consists of a number of ripened, fleshy pistils derived from a single flower. The black- berry and raspberry are excellent types. (h) The multiple fruit which consists of a number of small single pistils each derived from a single flower. The mulberry is a type. Although the blackberry and mulberry fruits show THE POME 85 a very striking superficial resemblance, they are radically differ- ent; the former representing a single, rather large flower with many pistils, and the latter a number of very small flowers, each having a single pistil. None of the above are true berries from the botanical viewpoint, but the name is so closely asso- riie peach, the drupe type of iiuit. ciated with them that it is practically impossible to make a change. The pome is a fruit in which the ovary, or ot^aries, the calyx and receptacle are united, both becoming fleshy. The tips of the sepals persist at the blossom end of the fruit and the 86 FRUITS AND SEEDS enclocarp develops as a papery core. The apple (Fig. 03), pear and qiiiiico are typical of this group. The true berry is a more or less leathery structure enclosing a mass of seeds. It may consist of the ovary only, or of the ovary enclosed in the cal^'x. Many plants belonging to a great diversity of families produce fruits of this type. Among the Fio. 63. — The apple, the pome type of fruit. most important are the gooseberry, huckleberry, cranberry, grape, orange, melon and cucumber. However, melons, cucum- bers and gourds and other fruits belonging to the family Cucur- hitacecp are frequently given a special name of " pepo." The accessory fruit is the fleshy receptacle of a single flower covered wuth achenes which are usually called seeds ; the straw- berry belongs to this t)'pe. The dry fruits are those in which the ovaries develop into dry pods. If this pod opens and releases the seeds it is dehiscent THE NUT 87 (Fig. 64, a), but if it does not open until burst by the germi- nating seed, it is indeliiscent. (Fig. 64, b.) The term pod or capsule will apply to any of the dehiscent fruits, regardless of the number of caiiDels involved in its formation. The term legume applies to those peculiar elongated pods (Fig. 64, a) of the legwriinoseoe or pea family, each of which represents a single capsule of two valves and a single placenta3. The indehiscent fruits are : (a) The achene, a small, dry, one-seeded pod representing one or more carpels. (Fig. 64, b.) Fig. 64. — ^a, legume or dehiscent pod ; b, an achene or indehiscent pod cut so as to show the enclosed seed; c, caryopsis or grain showing the pericarp or ovary, the integument or seed coat, the aleurone cells and the starch area; d, samara or key fruit; e, acorn or nut type. (b) The caryopsis or grain in which the pod or ovary is united to the seed. (Fig. 64, c.) (c) The samara or key in which the pod is developed into a thin flat wing. (Fig. 04, d.) (d) The nut is a single seed in which the ovary is developed into a hard, bone-like or horn-like covering. There are several types of nuts, such as the acorn (Fig. 64, e) which is a cup formed of involucral leaves ; the hazelnut, chest- nut, and beechnut, in which the nuts are enclosed in a pod also formed of involucral leaves ; the hichory nut inclosed in a shuck, probably composed partly of calyx and partly of involucral loaves, which tend to split when dry. The ivalnut is of the same type as the hickory nut, but does not tend to split; it is some- 88 FRUITS AND SEEDS what fleshy and resembles the drupes, ])iit the fleshy part is of an entirely diflerent origin from that of the trne drupes, F^g Type. — There are some fruits which are diflicult to classify in any of the preceding groups and must be distin- guished by special names. Among the most important is the synconium or fig fruit which is derived from an enlarged, soft, hollow stem enclosing a hirge number of very small flowers which are never exposed. Many people believe the fig produces fruit without blooming, but this is not true. Seed Distribution. — If seeds are to fulfill their place in nature they must be distributed over a considerable range of country. If they are all dropped within the immediate vicin- ity of the parent plant, the new plants will be too crowded, the weaker cannot survive, and the vigor of both parent and off- spring will be impaired. Seeds are mostly carried by wind and water, by animals and by man. It is very evident to the most casual observer that of the enormous quantities of seeds produced by a single plant, very few can ever serve their primary purpose in nature, that of producing new plants. The majority will be eaten by animals, or will fall in unfavorable places where they cannot germinate, while many of those that do germinate will never grow to maturity. (Fig. (55.) Carried by Water. — It is very easy to understand how seeds can be carried from place to place by water. Those that are buoyant will be carried along by streams, or float over the surfaces of lakes. Those that will not float may be carried along in the mud and debris. Heavy rainfall will carry many seeds for considerable distances and will frequently cover them with earth. Seeds that float are frequently propelled by wind and carried for long distances over lakes and other large bodies of water. Seeds from plants growing near the salt water will frequently be carried for long distances by means of water and wind and find a resting place on other shores. Of course, it is RESISTANCE TO HEAT, COLD AND DRYNESS 89 importaut that seeds, wliicli are carried in tliis manner, shall be of such character as not to be easily injured by long sub- mergence in water, and this is especially true of those seeds which are carried by salt water. The cocoanut is a striking example of a large floating seed which frequently is carried on the salt water. The vegetation of the volcanic and coral Fig. 65. — Devices for seed distribution. islands of the sea frequently owes its origin to seeds of this type. Resistance to Heat, Cold and Dryness. — The seeds of many plants are also, resistant to exti'cme drying and to extreme heat and cold. The seeds of some plants will lie in the soil for years waiting nntil the conditions are favorable for their germin- ation, while the seeds of other plants will perish in a few weeks or months, even when kept under the most favorable conditions. 90 FRUITS AND SEEDS Carried by Wind. — We have all observed the dispersal of seeds by means of the wind. Of course, strong air currents will carry light seeds for great distances, but many seeds have special structures which are very important in this work. The maple, ash and elm have membranous wings, or outgrowths by which the wind carries them. These outgrowths are a part of the ovary. The dandelion, lettuce, thistle and many other plants have seeds which are enclosed in the ovary {achenes), on which is developed a downy outgrowth serving as an air float, a sort of balloon or parachute. The seeds of the milkweed bear a superficial resemblance to those of the dandelion, but are quite different. You will recall that the dandelion is an inde- hiscent fruit, w^hile the milkweed is dehiscent. The outgrowth on the former is from the ovary ; on the latter from the seed coat. Some plants, especially weeds, of which the tumble w^eed is the most striking example, will break loose and be carried by the Avind for great distances, distributing their seeds as they travel. Carried by Man and Animals. — The lower animals are the involuntary carriers of many seeds, and man, the highest of the animals, is both an involuntary and a voluntary carrier. The seeds of many fruits will pass through the alimentary canal of animals unharmed and will grow if dropped in suitable places. Squirrels and other animals bury nuts and other seeds w^iich grow ; while birds accidentally drop the seeds of cherries, berries and other fruits, here and there. Burs and many other seeds have spines or hooks by which they cling to animals. Man carries many seeds in feed and bedding for himself and live stock, in packing materials, and in grain for various agricultural and commercial purposes. The shipping of grain and grass seeds from country to country has been the means of introduc- ing many of our most troublesome weeds. Seeds Thrown. — IMany plants have peculiar devices by which seeds are thrown for considerable distances. The touch- EXERCISES CONCERNING FRUITS AND SEEDS 91 me-iiot is an excellent illustration of this last method. The pod splits suddenly and the parts curl with such force as to throw the seeds out. EXERCISES CONCERNING FRUITS AND SEEDS 1- The Peach, — Examine the fruit of the peach. Wliat part of the flower is involved in its make-up? How many carpels does it represent? Note the fleshy exocarp, the hard endocarp and the seed. 2. Blackberry. — Examine the fruits of the blackberry or dewberry. What part of the flower? How many carpels? Where are the exo- and endocarps ? 3. Compare the fruits and tell how the blackberry diff"ers from the raspberry. 4. Compare the fruits and state liow the strawberry differs from the blackberry. 5. Compare the fruits and state how the mulberry differs from the blackberry. C. Apple. — Examine the fruit of the apple or pear. What parts of the flower are involved in its make-up? How many pistils and carpels does it represent? How does the endocarp differ from that of the peach? 7. Gooseberry. — Examine the fruit of the gooseberry. What parts of the flower ai-e involved in its make-up? How many pistils and carpels? What is the dry part on the tip? 8. Melon, Orange and Tomato. — Cut a melon or cucumber, an orange and a tomato in cross-section. Study in the same manner as the gooseberry. 9. Seedless Fruits. — Cut a navel orange and a luaiiana in cross-sec- tion and study in tlie same manner. How do they difi'er? 10. True Pods. — Examine the pod of a bean or pea or similar dry fruit. How many pistils? How many carpels? Where are the seeds attached ? 11. Examine as many other forms of pods as possil)le and answer the same questions. 12. Winged Fruits. — Study the seeils of tlic maple, dandidion, etc., for methods of distribution. 1.'5. Study the seeds of Uie milkweed and compare with tli(> dande- lion. 14. Burs. — Study burs, stick-tigiits and other seeds for special devices for distribution. 92 FRUITS AND SEEDS 15. Explosive pods such as the touch-me-not and witch luizcl slioulcl be collected. Note their explosive power. 10. Examine bladdery seeds and ovaries of such plants as may be available. QUESTIONS 1. What is a fruit? 2. What is a seed? 3. Give the different types of fruits. 4. Define each. 5. Give examples of each. 6. Give difi'erent methods of seed distribution and examples of each. CHAPTER VIII ANATOMY OF STEMS, ROOTS, AND LEAVES We have learned that stems are composed of strands of woody, fibrous material embedded in a softer substance or pith, and that this entire structure is enclosed in a water-proof sheath of epidermis or bark. We have also learned that the arrange- ment of these strands of fibrous material, which are known as fibro-vascular bundles, is different in the monocotyledonous and dicotyledonous stems. In the former (Fig. 66) they are dis- tributed throughout the stem except in those plants in which the stem is hollow, while in the latter they are arranged in a circle. (Fig. 67.) This difference in the arrangement of the mono- and dicotyledonous stems enables us readily to recognize these two groups of plants. (Chapter III.) Cellular Structure. — If we can examine cross and longitud- inal sections of a monocotyledonous stem with a microscope, we will find that the pithy part of the stem is composed of large, thin-walled cells. (Fig, 68.) We have previously referred to cells, but have not given an explanation of them. All parts of all plants are made up of cells of which this is the simplest type. The cell is the unit of the plant structure, the same as a brick or a stone may be the unit of a building. The name '' cell " was given by the students of botany, soon after the invention of the microscope, who saw the plant as a structure composed of many minute, apparently empty boxes or cells. Later students learned that these cells when young and active con- tained a substance which we now call protoplasm (Fig, 69), and still later students learned tliat protoplasm might exist with- out being enclosed in a cell-wall. Therefore, the definition of 93 94 ANATOMY OF STEMS, ROOTS, AND LEAVES a cell was protoplasm which may he either naked or enclosed in a cell-wall, or a small microscopic chamher from which the protoplasm has been withdrawal. The protoplasm is an albuminous substance more nearly like the white of an egg than any other substance with which we can compare it. It is that part of the plant in which the life is said to exist, and, so far as we know, is not different from the protoplasm of the animal cell. In its active condition, it is 66. — Cross-section of monocotyledonous stem showing arrangement of the fibro- vascular bundles. Fig. 67. — Cross-section of dicotyledonous stem showing arrangement of fibro-vascular bundle. Fig. 68. — Parenchyma cells. very sensitive to change of humidity, temperature, and to poison- ous substances. The active growing cells of the plant are rich in protoplasm, but many cells which persist throughout the entire life of the plant die and lose their protoplasm. In fact, the great bulk of the cells of most of our higher plants is dead. The cell can be studied to the best advantage in some of the water plants, especially the algae, which will be studied later. If we examine a very small amount of one of these plants known as Spirogyra under the microscope, we find that it is made up of a single row of elongated cells placed end to end. These cells appear to be rectangular, but they are cylindrical tubes closed at both ends. We very readily recognize the cell-wall and the chlorophyll, which is in a body known as the chromatophore. CELLULAR STRUCTURE 95 If we examine the cells of other plants, we find that these chrom- atophores vary greatly in size and shape. The other parts of the cell are not so easily recognized. But if we will keep some of the algae in alcohol for a few hours the chlorophyll will be partly or entirely removed so that we can recognize the very delicate layer of protoplasm lying next to the cell- wall and also delicate strands extending across the cell. This will be greatly aided by treating the algse with eosin or some other coloring matter which will stain the protoplasm. In this plant, the protoplasm does not completely fill the cell, but there are large spaces which are filled with water or air and known as vacuoles. We will also be able to recog- nize the nucleus which is a very import- ant part of the cell. The nucleus is protoplasmic in char- acter and very complicated in structure. It is present in nearly all living cells, and when the cell divides the nucleus also divides, one part going into each new^ cell. In a few plants, the cells are multinuclear, and when they divide some nuclei are found in each new cell. Cells also contain many compounds. The most prominent is the starch, which can be readily recognized by examining a very thin section of potato or apple under the microscope. If we treat this section with iodine, the starch grain. will turn blue. The starch grains of different plants differ in size and form ; this fact enables the microscopist to decide on amount and character of many adulterations of foods and drugs. The cells also contain sugar, fats, oils and other compounds which will be discussed later. (Chapter IX.) As the plant grows the cells undergo many changes and modi- fications. These variations are much more pronounced in the Fig. G9. — A typical plant cell showing protoplasm. 96 ANATOMY OF STEMS, ROOTS, AND LEAVES higher or flowering plants than in the lower forms. Some cells have thin walls and contain a great deal of food materials which make them valuable foods for man and other animals. Some are fibrous in character and have thick walls which make them Fig. 70. — Cross-section of fibro-vascular bundle from corn stem, Liscussion of useful in many industries. We will give a brief d these different types of cells. Parenchyma. — The cells of pith are large, somewhat vari- able in size, thin-walled, more or less spherical in shape and usually show irregular spaces between them. They are known as parenchyma or soft cells. (Fig. OS.) The great majority of the cells of fruits, grains and other edible parts of plants are made up of parench\Tua cells. Their EACH FIBRO-VASCULAR BUNDLE 97 value as food depends on the size of the cells, the thinness of the cell-walls, the amount and digestible character of the food (carbohydrates, hydrocarbons, proteids ; Chapter IX) which they contain, and the absence of poisonous or injurious compounds. Each fibro-vascular bundle is made up of a variety of cells. In the young bundle of the monocotyledonous stem (Fig. 70) is a small group of cells known as the cambium. They have the mmm Fig. 71. — Tracheary tissue. power of rapid growth and division and are primarily respon- sible for the increase in diameter of the monocotyledon stem. After a comparatively short time they lose the power of division and this checks the increase in diameter of the stem. On one side of the bundle will be a mixture of large and small cells constituting the woody part. Some of these cells have peculiar thickenings of the cell-walls forming rings, spirals, pits, etc. They are known as tracheids and tracheary cells. (Fig. 71.) On the opposite side of the bundle is a group of small, thick- vralled cells constituting the fibre or bast. (Fig. 72.) There are other types of cells which will be described later. A mono- cotyledonous stem increases in diameter for a limited time only, partly by the increase in the size of the fibro-vascular bundles 7 98 ANATOMY OF STEMS, ROOTS, AND LEAVES and partly by the increase in number of bundles. The hard outer covering of the corn and similar plants is composed of these fibro-vascular bundles. The dicotyledonous stem has bundles made up of the same kind of cells which are arranged very diti'erently. The outer part of the bundle contains the bast ; the inner, the woody cells ; and between the two groups lies the cambium which persists throughout the entire life of the plant. The cells of the cam- FiQ. 72. — Fibrous tissue; bast and wood cells. bium form a continuous layer of living, growing cells. These cells divide repeatedly cutting off innei* layers which go to form layers of wood and outer layers which eventually help to form the outer parts of the stem. All the other types of cells are derived from these cambium cells. Among the bast cells are the peculiar sieve cells (Fig. 73) or tubes, so called because of the peculiarly perforated cross walls. On the opposite side of the cambium are a number of cells and tubes which have peculiar thickenings on the inside of the walls. If the cells are short, more or less tapering at the ends and with numerous pits in the walls, they are known as traclieids, but if they are elongated into tubes in which the wall thickenings take the form of spirals, rings, pits, etc., they are known as tracheary tissue. (Fig. 71.) This term is also used to include the tracheids. This tracheary tissue is surrounded by long fihrous or irood cells. (Fig. 72.) The outer part of the bundle containing the sieve and bast cells is called the phloem region ; the inner part containing the trach- eary and wood fibre is called the Tylem region. THE DICOTYLEDONOUS STEM 99 111 the centre of the stem is the pithy stele composed of parenchyma cells. The libro-vascular bundles are also separated by masses of thin-walled cells called the medullary rays (Fig. 74), and the entire structure is enclosed in an epidermal mass of cells known as the bark. In soft stems of the herbaceous plants, geranium, etc., the bundles are separated by thick medul- lary rays while in hard, woody stems of the tree, the rays are very thin. In the stems or trunks of young trees, the bundles are Fig. 73. — Sieve tissue. '4. — Cross section of dicotyledonous woody stem, showing annular rings, medullary rays and bark. few and the rays thick, but the number of bundles increases and the rays become thinner and thinner with age. If we cut across a large stem, i.e., the trunk of a tree, we can readily recognize the small point in the centre which we call the pith or stele, the colored heart-wood, the sap-wood, and the bark. We will also note the great number of circles known as the annular rings. (Fig. 74.) In many trees, each ring represents one year's growth. We will also observe a large number of lines which radiate from the centre and are known as medullary rays. (Fig. 74.) In young stems these rays are composed of pareii- 100 ANATOMY OF STEMS, ROOTS, AND LEAVES cbjma cells aud are a coutiiiuation of the pith cells ; but in older stems they are frequently compressed into extremely thin, flat layers of cells separating the fibro-vascular bundles. The bundles increase in mnnber with the age of the plant. In young stems the bark is soft and greenish in color and can be readily separated from the underlying woody parts. In the older stems the outer bark is dead and frequently cracked and conceals the soft or true bark. In peeling the stem the separa- tion sometimes occurs in the cambium. The increase in the number of cells in the dicotyledonous stems is confined almost entirely to the cambium layer of cells which produces new cells for both the xylem and the phloem. Therefore, it will be readily seen that the formation of the new layers of xylem cells results in increasing the diameter of the stem without increasing the inner diameter of the cylinder of bark. This increase of the size of the stem must necessarily exert a considerable strain on the bark covering, which results in the very slow splitting and peel- ing of the outer bark. This explains the roughness of the bark of most of our trees and the characteristic natural peeling of many others. As the old, outer bark is gradually shed, the newly formed inner bark becomes the outer and new layers are formed from below. Cause of Annular Rings. — Tke formation of the cells of the xylem is not uniform throughout the season. In our northern climate, the cells formed in the first part of the growing season are larger and have thinner walls than those formed later. This difference causes the so-called annular rings. Sap-Wood.- — The light-colored sap-wood is composed of cells in which there is little or no growth, but which contain more or less protoplasm. Heart-Wood. — The dark-colored heart-wood is composed of cells from which the protoplasm has disappeared. They are THE ROOT 101 dead cells but are sound and give support to the trees. Souie- tiines the heart-wood decays aud the tree becomes hollow but continues to live and grow so long as the cambium is uninjured. The root (I'igs. 75 and 76) is composed of the same tissues as the stem^ but they are arranged in an entirely different man- ner. In the centre is the central cylinder or axis made up of iibro-vascular bundles which are separated by thin .layers of parenchyma. Immediately surrounding this axis is a compar- atively thick zone of parenchyma cells known as the cortex. This Fig. 75 Fig. 75. — Diagrammatic longitudinal section of root tip shewing: a, axis cylinder; c, cortex; e, epidermis; x, root cap. Fig. 76. — Cross-section of root tip showing cellular structure and root-hairs. is surrounded by a very thin layer of cells known as the epi- dermis. The epidermis of the very young roots gives rise to a great number of extremely delicate root hairs which penetrate the soil and take the water and necessary substances which may be in solution. (Page 26.) 102 ANATOMY OF STEMS. ROOTS. AND LEAVES The structure of the leaves varies somewhat in the different plants. Probably the most conmion form is that which we will describe. The typical leaf may be said to be composed of four layers of parenchyma cells supported by delicate frame work of fibro-vascular bundles. The upper layer of cells is the upper epidermis and consists of thick-walled, transparent cells ; below this is the layer of columnar or palisade cells which are elon- FiQ. 77 Fig. 77. — Cross-section of leaf showing: u, upper epidermis; p, palisade cell ophyll cells; 1, lower epidermis; s, stomata. Fig. 78. — Lower surface of leaf showing stomata. s; ni, mes- gated, more or less cylindrical and placed at right angles to the epidermal layer; just below the palisade layer is a thick layer of loose, irregularly shaped parenchyma cells known as the mesophyll; just below the mesophyll is the last layer or lower epidermis which is very similar to the upper epidermis. The palisadq cells are rich in protoplasm and in the green coloring matter which is known as the chlorophyll. The chlorophyll is usually confined to very definite small bodies known as chloro- plasts and is essential for the photosynthesis work of the plant. (Page 115.) EXERCISES SHOWING MINUTE STRUCTURES 103 In the lower epidermis will be found a considerable number of small openings or stomata (singular stoma) (Figs. 77 and 78), leading into the irregular tunnels or intercellular spaces found between the cells of the mcsophyll. Each stoma or open- ing is between two crescent-shaped cells called guard cells. The func- tion of these parts will be consid- ered in Chapter X. Hair-like Growth on Leaves. — The leaves of some plants are very smooth while others have more or less delicate hair-like growths known as trichomes, (Fig. 79.) (Chapter IV.) These trichomes are so numerous on the leaves of some plants as to give them the appearance of velvet. These structures are also found on the young stems of many plants. They are outgrowths of the epidermal cells and present numerous very interesting forms. Some of them are glandular in character, and cause the plant to feel sticky to the touch. They are, no doubt, protective in many ways. Fig. 79. — Trichomes or plant hair from leaf surface. EXERCISES SHOWING MINUT'E STRUCTURES 1. Pith. — Cut a vpry thin section of a pitli, mount in a drop of alcohol and glycerine and examine under the microscope. Note the large, tliin-walled parenchyma cells and the intercellular spaces between them. Tliey resemble a large number of thin hollow balls thrown together and slightly pressed out of shape where they come in contact. 2. Examine a small piece of algae (preferably Spirogyra) iinder the microscope. Note the size and form of the cells and the chromato- phore. 104 ANATOMY OF STEMS, ROOTS, AND LEAVES 3. Examine a small piece of algse that has been kept in alcohol and stained with eosin. Note the protoplasm and nucleus. 4. Examine a very thin section of potato under the microscope and note the starch grains. Stain with dilute iodine and examine again. 5. Cut a very thin crossi-section from the pith of corn stalk. Note the parenchyma cells and the fibro-vascular bundles. Study out the parts as indicated in the figures. l>. Geranium Stem. — Cut a very thin cross-section of the stem of a geranium. Note tlie parts as indicated in Figs. G7, 70. 7. Woody Stem.- — Cut a very thin cross-section of a twig from a tree. Note tlie, ])artii as indicated in Fig. 74. 8. Many Forms of Cells.— Make longitudinal sections of all of the above stems and find as many kinds of cells as possible. !•• Leaf Structure. — Hold a bit of a leaf between two pieces of pith and cut very thin cross-sections. Examine under the miscroscope and note tlie parts as indicated in Fig. 77. 10. Peel small fragments of epidermis from both lower and upper surfaces of a leaf and examine under the microscope. 11. Root Structure. — Hold a young root from corn or bean between two pieces of pith and cut very thin cross-sections. Examine under the microscope and note the i^arts as indicated in Figs. 75 and 76. QUESTIONS L Wliat do you understand by fibro-vascular bundles? 2. How are tliey arranged in the plant? 3. What do you understand by plant cell? 4. What are some of the difl'erent kinds of plant cells? 5. What do you understand by protoplasm? 6. What else do you find in plant cells? 7. Wliat is the cambium? Where is it located? 8. Explain the difference between mono- and dicotyledonous stems. 9. What is meant by phloem and xylem? Where are they located? 10. What are the medullary rays? , 11. What are annular rays? 12'. What is meant by epidermis? 13. In what parts of the plant do you find chlorophyll? 14. What is meant by mesophyll ? 15. What and where are the trichomes? CHAPTER IX CHEMICAL COMPOSITION OF THE PLANT We have examined both young and mature plants and have studied the various organs of which they are composed. We have also learned something of the structure of these plant organs. Let us learn something of their chemical composition ; something about the qualities that make them useful or unfit for food and other purposes. Of course, we have reason to believe that the different parts of the plant are unlike in chemical com- position, for we know that they are difi'erent in structure and texture, and that we use them for radically diiferent purposes. Water, Avhich is so essential for plant growth (Chapter I) is the most abundant and one of the most important compounds in the plant. We know that fruits and vegetables are juicy and we have seen the bleeding of trees when pruned too late in the season, and, therefore, it is not necessaiy to demonstrate that plants contain water. The quantity of water in the diiferent parts of the plant varies from the very large amounts in juicy fruits to the very small amounts in dry grains. The following table shows some of the extremes : Percentage of mater content Plant hy weight Cucumber ( fruit) 96 Cabbage ( leaves ) 90 Beets, red (roots) 88.5 Apples (fruit) 83.2 Potato (Irish) 78.9 Potato (sweet) ' 71.1 Corn (green fodder) 79.8 Corn ( dry grain ) 10.9 We also know that plants contain carbon, for we have seen the charcoal which is fonued as a result of burning a piece of 105 106 CHEMICAL COMPOSITION OF THE PLANT wood. But when the fragment of charcoal is burned we have a few ashes remaining. The chemist tells that this ash contains small quantities of phosphorus, potassium, calcium, mag- nesium, sulphur, sodium, chlorine, manganese, aluminum, etc. The water, carbon and nitrogen which we know make up a con- siderable part of the plant have been carried oti" as vapor and gas during the process of burning. The Avater is composed of two gaseous elements, hydrogen and oxygen. When wood burns or decays, the carbon (C ) unites with the oxygen (O) of the air forming a gaseous compound known as carbon dioxide (COo), which is available for new plant growth. (Page 115.) Starch. — We also know that plants contain starch W'hich is composed of three elements, carbon, hydrogen and oxygen, com- bined as C^HioOg. Starch is one of the most abundant plant substances and is one of the valuable plant products of com- merce. It constitutes a considerable part of the dry substance of seeds, green fruits, fleshy roots, tubers, bulbs, fleshy leaves, etc., in which it can be readily detected by very simple experi- ments. Starch is one of the important food substances for both man and beast. Potatoes, sweet potatoes and other tubers and fleshy roots contain large quantities of starch. Grains, peas, beans and other seeds contain an abundance of starch. The starch not only makes these plants valuable for food but also for other purposes. Tapioca, some forms of paste and other ar- ticles of commerce are made from starch. The following table shows the relative amount of starch found in some common food plants, as estimated in percentage of dry weight. Plant products Percentage of starch Seeds of navy beans 45 Seeds of i>eas 52 Seeds of corn fiO Seeds of wheat GS Seeds of rice 68 Thibers of potatoes 80 FAT8 107 The starch is found in definite bodies known as starch grains within the cells of the plant, and can be seen readily with the aid of the microscope. The size and form of the starch grains vary in different plants. Sugar is another plant product very similar to starch, but it occurs in a much greater variety of forms. The most com- mon type is the cane sugar (CoHioOg) which is abundant in many plants and forms a valuable food product. It is found in the cell-sap and can be readily detected by simple experiments. It is especially abundant in sugar beets, sugar maple, sugar cane and ripened fruits. We all recognize the value of sugar for food and as an article of commerce. One of the great prob- lems of the plant breeders is to increase the percentage of sugar in the sugar-producing plants. (Chapter XV.) The amount of sugar in the sugar beet has been increased from 7 to 15 per cent by scientific methods of plant breeding. Carbohydrates, — The cell-walls are composed of cellulose which is made up of the same elements as starch and sugar, but they are also infiltrated with various other substances. Cellu- lose is the most important plant compound in the manufacture of paper. Cellulose is also used extensively in the manufacture of the many celluloid articles on the market, and it is also used in the making of gun cotton and other high explosives. Many plants also produce gums which are composed of these same elements and some of which are important articles of com- merce. The starch, sugar, gums, and cellulose are known as carbohydrates ; that is, their hydrogen and oxygen is always in the ratio of two to one. Fats. — Many plants also contain fats and oils which are composed of the same elements as the carbohydrates (i.e., hydro- gen and oxygen), but the hydrogen and oxygen ratio is never two to one. The fats and oils are known as hjjdrocarhons and are usually most abundant in the seeds, especially nuts. They 108 CHEMICAL COMPOSITION OF THE PLANT are used for food, medicine, soap making and many other pur- poses and are among the most important articles of commerce. Proteins. — Plants also contain a third group of foods, known as proteins or proteid foods which are composed of carbon, hydrogen, oxygen and nitrogen, and are among our most im- portant food substances. They are especially abundant in seeds and the food value of many plants over others depends almost entirely on their percentage of protein. They may be associated with the carbohydrates, but in some cases are borne in separate cells. The great value of clover, cowpeas, soybeans and related plants for stock feed, and of beans and peas as food for man depends primarily on their protein content. Plants contain many other compounds, some of which are referred to as waste products. Among the most important of these compounds are the following: (a) The essential (or volatile) oils, w^hich are entirely different from the true oils previously referred to. They may occur in any part of the plant, but are especially abundant in the foliage and flowers. Most of the odors of plants are due to these essential oils, many of which are extracted and used in the manufacture of medicines, perfumes, soap and other articles of commerce. (b) Gums and resins of various kinds are familiar articles of commerce. Among the most important are turpentine, resin, balsams, gum-camphor, gum-arabic and gum-tragacanth. (c) Organic acids are very numerous and are especially abundant in certain fruits. Among the most common organic acids of commerce are oxalic, malic, tartaric and citric acids. (d) Tannins are abundant and are found in the great ma- jority of the higher plants. They are used for the making of hides into leather, in medicines and for other purposes. (e) Alkaloids are abundant plant products from which we obtain many valuable medicines and some of our most danger- EXERCISES, COMPOSITION OF PLANT TISSUES 109 ous poisons. Among the most familiar are quinine, strychnine, cocaine and morphine. In this connection, it is well to remem- ber that about 90 per cent of our medicines are of plant origin and that much of the early work in botany was for the discovery of new drug plants with which to relieve the sufferings of mankind. EXERCISES SHOWING THE COMPOSITION OF PLANT TISSUES 1. Ash in Leaves. — Weigli a bunch of green cabbage or lettuce leaves. Dry tliem in an oven. Weigli again and compute percentage of water. Burn tlie leaves, weigli and compute the percentage of ash. 2. Water in Seeds. — Ptit a few seeds in a test tube, plug with cotton and heat gently so as not to scorch the seeds. Hold the tube as nearly horizontal as possible while heating. Do you see signs of water on the glass? 3. Ash in Wood. — Put a piece of wood in a test tube and heat until a piece of charcoal (carbon) is formed. Burn the charcoal to ashes. Shake tha ashes in water. Do they dissolve? 4. Tests for Starch and Sugar. — Put a little commercial starch and a little sugar in separate test tubes of water, and shake. Do they both dis- solve? Add a few drops of iodine to the starch and note the change in color. This is the test for starch. Add a small amount! of Fehling's fluid, a few drops at a time; a brick red color indicates the presence of sugar. This test will not work with cane sugar unless the solution has been boiled with dilute acid before adding the Fehling's fluid. Fehling's solution can be made in the laboratory. It consists of two solutions: (A) 30.04 grams of pure powdered copper sulpliate in 200 c.c. of water. {B) 150 grams of Rochelle salt and 50 grams caustic soda in 500 c.c. of water. Keep the two solutions separate and mix before using as follows: 2 parts of solution A. 5 parts of solution B,. 10 parts of water. 5. Carbon in Sugar. — Put a little sugar in a test tube and heat slowly until you have a black mass of carbon. Note what occurs during the process and explain. 6. Testing Seeds and Fruits. — Test fruits, tubers, fleshy roots and various other parts of plants by applying the starch and sugar tests to freshly cut surfaces. 7. Examining Potatoes and Apples. — Cut very small, thin slices of no CHEMICAL COMPOSITION OF THE PLANT potato and apple, mount in water and examine under the microscope. Add a drop of iodine and not*» the effect. 8. Starch and Sugar after Germination.— Crush a few well ger- minated seeds and put in two test tubes, fill about one-third full of water and shake thoroufilily. l?oil and test for starch and sugar. 0. Changing Starch to Sugar. — Make a thin paste by boiling starch in two test tuljes of water. Allow to cool and add a small amount of diastase or saliva to one. Keep in a warm place for 24 hours and te^ both for sugar. 10. Oil in Seeds. — Crush a seed of castor bean or the kernel of some nut between tlie fingers and thumb and note the oily character. Rub the seed or nut on a piece of paper for the same purpose. Tie a small amount of cruailied seeds or other plant material in a bit) of cheese-cloth and soak in a small dish of benzine; squeeze and remove and allow the benzine to evaporate. Any oil that may be present will be found in the dish. Make a list of vegetable oils of commercial importance and give their sources. 11. Protein in Flour. — Tie a small quantity of wheat flour in a bag and knead under a stream of water. Tlie sticky dough that remains is largely protein. Tlie starch was mostly washed out by the stream of water. 12. Starch and Protein in Wheat.— Cut very thin slices of wheat grain and examine under the microscope. Test for starch. Note that tlie starch is in the center and in very thin-walled cells. Also note that the proteid (aleuronc) is in cells surrounding the starch. Also note the hull is made up of the union of seed and ovary coats. QUESTIONS 1. \\']iat compound is found in greatest amount in the jilant? How does it get into the plant? Is the total amount entering the plant retained? If not, how does it pass out? 2. Explain the results obtained in the drying and burning of a piece of wood. How do these elements and compounds become a |»art of the wood? 3. What substances found in plants are useful as foods for animals? In what parts of the plant are they found? 4. Give a list of commercial products of plants. Tell where found and their uses. 5. Mention several plants or products rich in sugar, fi. From what plants is starch obtained commercially? 7. What plants yield oil for commerce? 8. ]\Iention several stock feeds rich in protein. i CHAPTER X PLANT FOODS AND PLANT GROWTH We have learned something about the important substances found in phmts, the starches, sugar, oils and proteids which make them valuable for food. We have also learned that they con- tain many other substances of more or less value in commerce. We also know that many plants are gi-own for their fibre which is used in many manufacturing industries, and we also use the wood of many of the larger plants for many purposes. There- fore, it is very evident that the plant kingdom produces a very large number of useful plants. Let us now study the source of these products and the processes by which they are formed. Plants are unlike animals in that they use comparatively simple compounds which are obtained from the soil and air and transformed into true food materials for their own gi-owth ; animals cannot use such simple compounds, but are compelled to feed upon plants from which they secure already manufac^ tured or true foods, carbohydrates and proteids. Therefore, all animal life is dependent either directly or indirectly on plant life for its existence. The most important raw foods or com- pounds that the plant gets from the earth are water (H2O), ammonia compounds (Nil.,), sulphur, potassium and phos- phorus, and various salts. The most important raw foods from the air are carbonic acid gas or carbon dioxide (COo) and very small amounts of oxygen (O). The energy with which these raw materials are transformed into true foods comes from the sun in the form of heat and light. Therefore, all life (both plant and animal) upon the earth is dependent upon the sun for its existence. These raw foods are transformed into true foods in the plant before they can be 111 112 PLANT FOODS AND PLANT GROWTH used even for its own growth. However, the process by which these simple compounds are transformed into true food materials is imperfectly understood. The amount of water in the soil varies with the amount of rainfall and the texture of the soil. Coarse, sandy soils are poor retainers of waiter as compared with the very fine clay soils. Humus soils are excellent retainers of water, and this fact, together with their richness in organic matter, makes them espe- cially good for agricultural purposes. It is very evident that water acts as a solvent for the available soil substances and salts, and is then taken up by the root-hairs. We have already studied the root-hairs, and know that they are long, delicate cells containing very active living protoplasm and a watery sub- stance called cell-sap. This cell-sap is -water containing salts, acids and sugars. The root-hairs are evidently well filled and somewhat distended. When cells are distended in this man- ner they are said to be turgescent, or in a state of turgor. All the active cells of a normal, growing plant are turgid and it is this condition which enables the soft parts of a plant to main- tain their form and position. When cells lose their turgidity the plants wilt. Osmosis. — It is well known that when a substance dissolves in a liquid it gradually diffuses until equally distributed. If two solutions of equal density are separated by a plant or animal membrane, the substances in solution will gradually dif- fuse through the membrane until the two solutions are uniform throughout. This is known as os/ho.s/.s. (Fig. 80.) If two solu- tions of unequal density are used there will be a flow from the less dense to that of the greater density. Wlien a plant is growing under suitable conditions, the solution of greater dens- ity is within the cells, especially the root-hairs ; and the solution of lesser density surrounding them. The delicate root-hairs ramify among the extremely fine particles of soil. The soil, OSMOSIS 113 water aiid the salts in solution pass into the cells of the root- hairs and thence into the fibrous and tracheary tissues of the root and thence through the same and probably other tissue of the sap wood of the stem into the leaves where a considerable part of it is given off by transpiration. (Chapter VIII.) The exact process by which water passes through a growing plant is FiQ. 80. — Apparatus for demonstrating osmosis; thistle tube on left and egg on right. not understood. Some of the acid within the root-hairs passes out (exosmosis) and helps to dissolve the raw food compounds in the soil, thus making them more available. If the character of the soil is such that the water solution is of greater density than the contents of the plant cells, the plant cannot live in it, and if a plant should be set in such soil it would wilt very quickly because of the loss of water which would pass out to the soil. s 114 PLANT FOODS AND PLANT GROWTH Transfer of Water. — The process by which water is trans- ferred from one part of the plant to another part is very imper- fectly understood, but we do know that it is transferred from place to place and t-uat it is carried upward in great quantities against the tremendous force of gravity. We know that the force necessary to lift this column of water to the top of very tall trees must be enormous. We know also that this activity is much greater at certain seasons of the year than at others. We have all observed the bleeding of trees and vines when pruned too late in the spring, and know that considerable injury may result from this practice. Transpiration. — We have said that a considerable amount of water is given oif through the leaves by transpiration. This is also true of the new shoots and such other green parts as the plant may possess. The transpiration of water should not be confused with evaporation. The latter process takes place from the free surface of a body of water and is controlled by the physical conditions of the air, but the former is controlled by the structural character of the plant and the living protoplasm of the plant cells. The water in the plant must pass through the cell-walls into the intercellular spaces of the mesophyll to which we have previously referred (Chapter IV), and then passes out through the stomata by a process of diffusion. Of course, when the air is dry the transpiration of water will be much greater than when moist. The number of stomata varies greatly in different species of plants, those growing in dry places usually having fewer than those growing in wet places. The amount of water which plants take from the soil and give out through the leaves during a growing season is enormous, but extremely variable when we compare plants living under different conditions. It is estimated that some of our common farm crops take up and give off an average of 300 pounds of water in the production of one pound of dry material, although in some plants it is three times this amount. THE FORMATION OF CARBOHYDRATES 115 A Change of Gases. — The giviug olt' of water through the stomata is associated with a change of gas by transfusion be- tween the air within the intercellular spaces of the leaf and the air on the outside. Therefore, as the water passes outward through the stomata, the carbon dioxide (CO2) of the air passes into the intercellular spaces, is absorbed by the protoplasm of the mesophyll cells and immediately dissolved in the cell sap, thus forming carbonic acid (COa+HaO^CHaOg). The action of the sunlight on the chlorophyll results in the breaking up of this carbonic acid and the recombination of the elements with the elements of water into other compounds. This delicate and complicated process is very imperfectly understood, and the first result that we can recognize with any degree of certaint}^ is glucose or grape sugar (C,;H,oO,;). Plants and Animals Help Each Other.^We know that the process results in the liberation of free oxygen (6CO2 + 6H0O ^C6H^206+120) which is given out through the stomata and is essential for the life of animals. Therefore, we see that ani- mal and plant life are more or less inter-dependent, but it is very evident that animals are more dependent upon plants than plants are upon animals. Plants utilize the carbon dioxide which is exhaled by the animals, but they could readily obtain this supply from other sources. Animals utilize the oxygen given off by plants, and are absolutely dependent upon plants for their food supply. The formation of carbohydrates, that is, starches and sugars, from these crude materials (water and carbon dioxide) by the action of sunlight on the chlorophyll is known as photo- synthesis and is the most wonderful and most mysterious process in all nature. With this as a beginning, we have the basis for the formation of innumerable other plant and animal products. A small part of this organized food is used immediately for cell formation and growtli, but the greater part is stored for fu- ture use. 116 PLANT FOODS AND PLANT GROWTH Grape sugar Avliicli is formed in the green parts of plants can be readily transformed into starch by the loss of one molecule of water (C,;HioOo — H2O = CcHioOg). In some plants, such as the sugar beet and sugar corn, the sugar is transferred directly and stored as such without change. But in most plants it is very quickly transformed into starch, which is reconverted into sugar during the night and transferred to other parts. Therefore, if the leaves are examined early in the afternoon they will be found to' be very rich in starch as compared with their condition before sunrise. Other Organic Compounds Formed. — We know that search and sugars are the most abundant food products of the plant; that they are especially abundant in vegetables, fruits and seeds. But we also know that there are other substances, such as hydro- carbons (fats and oils) ; and the proteins, which contain nitro- gen (and some sulphur and phosphorus). These are among the most important food products, but we know very little about their formation. Mineral Substances. — Plants take a great many minerals from the soil. The most important are phosphorus, potassium, calcium, magnesium, sulphur, iron, sodium, chlorine, silicon, manganese and aluminum. These elements go into solution in the water of the soil and then pass into the root-hairs in the manner already described. They may be found by making a chemical analysis of the ash of the plant. They vary in pro- portion in different species of plants, in plants at diiferent ages and in different parts of the same plant. These minerals exist in varying quantities in the soil, but their proportions may not be such as are needed by the crop, or they may not be in such form as to be available as plant food. Therefore, the progressive farmer, who is familiar with his soil and with the needs of his crop, makes use of manures and commercial fertilizers to overcome these deficiencies. Nitrogen and Protein. — One other most important element IMPORTANCE OF HUMUS 117 of plant food wliicli we have not taken into consideration is nitrogen^ an element which is essential in the formation of protoplasm and protein. The food value of many plants de- pends upon their protein content. I^itrogen constitutes 78 per cent of the atmosphere, and one might readily suppose that the plant could secure its supply from that source. But such is not the case. The free nitrogen of the air is not available for plant food. It must be united with hydrogen to form a nitrate before it can be uti- lized by the growing plant. There are several sources of nitrogen for plant food. (a) By the decay or disintegra- tion of organic matter; i.e.j dead plants and animals and their waste products. This is brought about by millions of minute organisms of decay known as bacteria. (6) By certain soil bacteria which live in the tubercles or no- dules (Fig. 81) on the roots of legu- minous plants and which enable the plant to take the nitrogen from the hydrogen, thus forming ammonia compounds. (c) By rainfall, which carries tlie nitrogen of the air to the soil where it becomes available for these bacteria. (d) By electrical discharges (lightning) producing nitrous and nitric acids which are carried to the earth by the rainfall. The first and second of these are the most important. Importance of Humus. — The first of these sources shows the importance of utilizing animal manures and decaying plant materials as fertilizers. These decayed animal and plant prod- FiG. 81. — Root of legume showing tubercles. lir, and combine it with 118 PLANT FOODS AND PLANT GROWTH nets are called Jiunius, and we Lave long recognized that liunms is essential for plant growth. The second shows the importance of the use of leguminous plants to increase the nitrogen content of the soil and explains why clovers, alfalfa, cowpeas, soybeans, vetch and similar plants are of such great importance as soil improvers. Circulation. — Knowing that plants take in water from the soil, that it rises through the plants and is given off through the foliage, naturally indicates that the plant possesses a circulatory system similar to that of animals. Although the circulation is through definite parts of the plant tissues, it is not through a definite set of tubes and does not have a propelling organ or pump such as the heart of the animal. The water rises in the wood (or xylem) part of the stem and carries the mineral substances of the soil in solution. But this does not complete the problem of circulation. Very little of the manufactured plant food is stored in the parts in which it is formed but is transferred to fruits, seeds, tubers, bulbs, roots and other parts for storage. This transfer is primarily through the outer (or phloem) part of the stem. We do not understand just how this transfer is accomplished, but much of the food must undergo modifications, must become soluble, before it can be moved. The carbohydrate is probably moved while in the form of sugar (glucose), and the fats and true soils as glycerine and fatty acids, and the proteids in a form known as amides. EXERCISES SHOWING PROCESSES IN PLANT GROWTH 1. Osmosis Through a Bladder. — Tie a bit of bladder or sausage casing or parchment over the large end of a thistle tube; partly fill the tube with molasses and immerse the large end in water until tlie two liquids are on a level. Make observations at intervals of one hour and explain tlie phenomena. 2. Exosmosis and Endosmosis- — Peel some fleshy root such as car- rot, turnip or beet and cut in slices about % x 1^,4 inches and about Vs inch in thickness. Put a few of them in distilled water and a few in a salt or sugar solution. Examine after a few hours and explain. Now EXERCISES SHOWING PROCESSES IN PLANT GROWTH 119 transfer tliem, putting those that were in the solution in the distilled water, and those that were in the water in the solution. Examine after a few hours and explain. 3. Movement of Plant Fluids. — Cut * a stem of a Begonia two or three inches from the surface of the soil, and place the severed part in a glass of water that has been colored with some analine dye or red ink. After twenty-four hours, remove and cut the stem at various points and examine. Fasten a small glass tube on the stump by means of adhesive tape, and keep the roots well watered. Note the rise of water in the tube. Explain. 4. Transpiration. — Take a small actively growing plant and tie a piece of sheet rubljer over the pot allowing the plant to project through a small opening; invert a glass over the plant and note the moisture which collects within the next few hours. Where did it come from? Cut a bunch of fresh growing plants or a cabbage and weigh. Allow to wilt and dry and then weigh again. Dry in an oven, but do not char, and weigh again. Explain. 5. Plant Food. — Secure a quantity of coarse, clean sand, and fill two flower pots or cans of equal size witli equal quantities. Plant several grains of corn of approximately the same size and character in each. Water one from time to time with rain water or distilled water and the other with soil solution. Soil solutions may be prepared by filling a larga pail two-thirds full of rich soil or well rotted manure and then adding enough water to make a thin slop. Stir, allow to settle and draw off the water. I'efill witli water and allow to stand until needed again. In which pot do the plants grow best? Why? 6. Moisture in Wood. — Weigh a piece of green wood. Heat until thoroughly dry. Weigh again. What has it lost and how much? 7. Carbon in Wood. — Burn the wood imtil charcoal is formed. This is almost pure carbon. Weigh again. What has been lost and how much? 8. Ash in Wood. — Burn the charcoal. What have you remaining and how much? 9. Carbon in Sugar. — Put a little white sugar in a test tube and heat. What happens? Explain. 10. Study of Oxygen. — Mix a teaspoonful of potassiiun chlorate with about one-fourth the amount of finely powdered manganese dioxide. Put the mixture in a large test tube or small flask. Close the container with a stopper through which a small delivery tube passes. Fix the con- tainer in a slanting position on an iron stand, and run the free end of the delivery tube into a tray of water. Heat the mixture gently with gas or alcohol flame. Fill several bottles with water; invert one over the mouth of the delivery tube in such a manner that the water will be * The stem should be held in the liquid during the cutting so that the cut surface is not exposed to the air. 120 PLANT FOODS AND PLANT GROWTH forced out by the gas. When all the water has been forcod out, cover the mouth of tlie bottle with a card and invert. Repeat until three or four bottles are filled. This gas is oxygen. Note its color. Thrust glowing pieces of char- coal into the bottles and note the result. Explain. 11. Study of Carbon Dioxide. — Put some small fragments of marble into a flask thoroughly closed with a cork through which has been passed a delivery tube as in; Exercise 10, and a small funnel or thistle tube. Pour dilute hydrochloric acid into the funnel until the lower end is covered. Collect the resulting gas (carlwn dioxide) as in Exercise 10. Run a little of the gas into lime water and note the result. Take a little fresh lime water and blow into it through a straw or tube. Note the result. Explain. 12. Burn a piece of charcoal in a l)ottle of pure oxygen. Remove quickly, pour in lime water and shake. Note the result. Explain. 13. Study of Hydrogen. — Put a few fragments of zinc into the same or a similar apparatus as used in Exercise 10. Add the dilute hydrochloric acid but allow the gas to be given ofl' for some minutes. Then collect a bottle of the gas (hydrogen) and place upside down on a table. Darken the room and thrust a burning match into the inverted bottle. Note the result. 14. Study of Nitrogen. — Fasten a bit of candle to a cork and float in a vessel of lime water. Light the candle and cover with a wide bottle so placed that the edges are under water. When the candle goes out, cover the mouth of the bottle with card-board or cork and reverse so as to retain all the water that has risen in tlie l)ottle. Shake thoroughly, and allow to stand until the upper part is clear. What has been used by the burning candle? What gas has Ijeen formed as indicated by the lime water in the bottle? The gas remaining in the bottle is nitrogen. QUESTIONS L What are the three great groups of substances found in plants? 2. Of what elements are each of these food substances composed? 3. What are the sources of these elements? 4. What otlier elements are found in plants? 5. What relation does the texture of the soil bear to the water con- tent? 6. What do you understand by humus? 7. What do you understand by turgor? 8. What do you understand by osmosis? 9. Why do plants wilt? 10. What do you understand by transpiration? 11. What do you understand by piiotosynthesis? CHAPTER XI THE GYMNOSPERMS Thus far we have devoted our time to the study of the higher plants, that is to the plants v^hich produce flowers and seeds. This great group of trees, shrubs and herbs presents by far the most conspicuous types of vegetation and includes our most important agricultural crops. But we must now con- sider the gijmnosperms (for classification, see Chapter V), that great group of seed-bearing plants which do not produce true flowers. They are also called coniferous or cone-bearing plants because of the cones which contain the seeds. The largest, most important and best-knoAvn gToup is the order Pinacece which are widely distributed throughout the world especially in the northern hemisphere. They are the pines, spruces, firs, bal- sams, larches, cypresses, cedars, hemlocks, arbor vitse and the giant red oaks of our Pacific coast. Structure of Stems. — The general character and gross struc- ture of the stems and roots is somewhat similar to the angio- sperms, but the leaves are modified until in most cases they are described as needles. These needles may be compared to the midrib of an ordinary leaf, but when cut in cross-section and examined under the microscope they show a thick cuticle and epidermis covering a few layers of sclerenchyma cells (Chapter VIII), which in turn cover the chlorophyll bearing parenchyma (Chapter VIII). The small size and peculiar structure of the leaves make them especially well suited for withstanding either dry or cold climates. Most coniferous trees shed their needles gi\^dually and, therefore, are in foliage the entire year. For this reason they are known as evergreens and are especially suit- able for ornamental plantings. Some few conifers such as the 121 122 THE GYMNOSPERMS bald cypress and larch are deciduous, i.e., shed their entire foliage each year and are bare during the winter season. A cross-section of the stem will show the annular rings and medullary rays the same as in dicotyledonous plants. Very thin sections should be made and mounted in water for study under the microscope. Each section is cut at right angles to the other two as follows : (a) The cross-section which will show the varying thick- nesses of the cell-walls by which the annular rings are produced, the large thin-walled cells of the late summer growth. It will also show the medullary rays and large resin ducts. (&) The radial section which is cut longitudinally and on a plane passing through the axis of the tree {i.e., quarter sawed) will show the peculiar markings of the cells (tracheids). By studying care- fully made tangential sections which are also longitudinal but at right angles to the radial section we can get some idea of these peculiar markings. The cones are of two kinds, staminate and pistillate. They correspond to bunches of staminate and pistillate flowers. We are most familiar with the pistillate (or carpellate) (Fig, 82, c) cones and will give them first consideration. They become the mature cones which we find hanging on the trees. These cones are made up of scales, corresponding to needles or leaves, but instead of being arranged in circles as in the case of a true flower, they are arranged in spirals. You will also note that when they spread apart they each bear two mnged seeds. But let us examine an immature cone such as we will find early in the spring. (Fig. 82, c.) Each cone is small and the scales naturally spread so as to expose two ovules (macrosporan- gia) . (Fig. 82, d. ) This is quite different from the true flower- ing plants in which the ovules are always enclosed in an ovary. Pollination.— Tn the spring we will also find clusters of very small staminate cones. (Fie;. 82, a.) Each scale of these POLLINATION 123 small cones is a stamen (sporophyll) bearing sacs (microspor- angia) filled with great quantities of yellow pollen grains {microspores) which fall in showers and are scattered by the wind. These pollen grains are provided with liattened exten- sions of the cell-wall, forming wings for their ready support in the air. t<56 FiQ. 82. — a, cluster of staminate cones; b, pollen grain; c, pistillate cone; d, scale from pistillate cone showing two ovules. Some of the pollen is canght in the pistillate cones and falls upon the exposed ovules. The scales close and the pollen grain produces a delicate tube which penetrates the ovule, reaches the egg and results in fertilization similar to that described for the angiosperm. (Chapter VI.) This process cannot be followed except by the study of carefully prepared slides with the aid of the microscope. However, the interval of time between pol- lination and the maturity of the seed is much greater than in most angiosperms. The seed cone enlarges rapidly, but tlie seeds are not mature until late in the summer of the following- year. 124 THE GYMNOSPERMS Cycadales. — Another very interesting group of the gtjmno- sperms is the order Cycadales which is mostly tropical in habit. In this order we find the Cycas revoluta which is frequently grown in greenhouses. Its chief point of interest botanically is in the fact that it possesses many characters in common with the ferns and forms a sort of connecting link between the Gymno- sperms and the Pteridophytes or ferns. We all readily recognize the great value of the Gymno- sperms. Many of them are among our most important forest trees from which we derive enormous amounts of lumber for building purposes and cabinet making. They also furnish our commercial supply of turpentine, resin and balsams. The cypress is used extensively for telegraph and telephone poles. The use of evergreens for ornamental plants is directly con- nected with the nursery business and landscape gardening and involves very large expenditures of money. EXERCISES WITH GYMNOSPERMS 1. Examine a number of evergreen trees and note their straight shaft, mode of branching and general form. 2. Growtli and Leaves of Pines. — Examine a pine tree and note the long shoots that are produced each year. Also note the short shoots composed of clusters of needles. Count the needles in the clusters in the different kinds of pines that may he available. Is the number constant for each species? 3. Examine a needle carefully; make crosshsections by cutting the needle in a bit of pith and examine under the microscope. Note the thick cuticle, the thick epidermis, the sclerenchyma and the chlorophyll-l)earing parenchyma. 4. Twigs of Cone-bearing Trees. — Cut across radial and tangential sections of a brancli from a cone-bearing tree and examine under the compound microscope and note the points referred to in the text. 5. Cone Flowers. — Examine young staminate and pistillate cones and note the points referred to in the text. (This material can be col- lected in the spring and preserved in alcohol or formalin.) G. Pollen Grains. — Examine some of the pollen grains under the compound microscope. QUESTIONS 125 7. Seeds and Cone. — ■Examine a mature cone. Remove some of the and examine. 8. Study Seedlings. — Plant some of the seeds and note eliaraeters of the seedlings. 9. Greenhouse Gymnosperms. — Visit the greenhouse and ask to see a Cycas revoluta. QUESTIONS 1. What do you understand by Gymnofiperms:^ 2. Compare the leaf of iii Gymnosperm with that of an Angiosperm. 3. What do you understand by deciduous? 4. Are any of the Gymnosperms deciduous? 5. Have you seen any of these in tlie winter condition? (i. Name the parts of the staniinate and pistillate cones of a con- iferous tree. 7. Compare these parts with the corresponding parts of a true llovv- ering plant. CHAPTER XII ECOLOGICAL RELATIONS The growth of the phiiit is influeiiced by many factors, among the most important of which are water, soil, temperature and light. The combination of these four factors may not be such as to give the maximum in growth and productiveness; for while one or two of these factors may be in the correct pro- portion for the best growth of the plant, the other two may be in proportion unsuited for the greatest possible development. The plant is also influenced by animals, wind currents, and many other factors too numerous for discussion at this time. When a factor is such as to kill or prevent the growth of the plants of any particular species, it becomes a limiting factor in the spread of the species regardless of the character of the other factors. Lack of water may prevent the spread of a species into a territory when all other factors may be satisfac- tory. This is well illustrated by the great desert regions of the world which produce abundant vegetation when subjected to irrigation. Any species of plants will extend its range as fast as the controlling factors will permit, and will reach its max- imum development where the combination of the factors is best suited to its existence and its minimum where it is most unsuitable. Water. — We have already learned that plants cannot live without water and that it is the most abundant compound in most plants and also one of the most important. It passes into the plant by means of the root-hairs and passes out of the plant by transpiration, mostly through the leaves. We have also learned that many plants are composed almost entirely of water. How- ever, plants differ in the amount of water required for their 126 THE HYDROPHYTE SOCIETIES 127 existence. Some plants float in the water and have no direct connection with the soil ; others are rooted to the soil but float in the water (water lilies). Some are rooted in the mud but extend fan above the water (cat-tails) ; some grow in wet soil; still others grow in dry soil and are easily killed by too much Fig. 83. — Zone formation of vegetation dependent upon depth of water. water. These facts enable us to group plants into societies de- pendent upon their water requirements. (Figs. 83 and 84.) The Hydrophyte societies are made up of those plants which live in the water or in very wet swampy soils. Ponds and lakes in which the water varies in depth frequently show many of these societies to an advantage ; the floating plants in the moder- ately deep water, the cat-tails near the margin and the willows on the margin. Rice is one of the few hydrophytes which is of great agricultural importance. 128 ECOLOGICAL RELATIONS The Mesophyte societies are those made up of plants which require a fair amouut of rainfall. The forest and prairie plants and most of our agricultural plants are mesophytes. The Xerophyte societies require very little water and in- clude the desert plants. Fig. 84. — Zone formation of vegetation dependent upon depth of water. In addition to these societies we have also The Halophytes or those plants which grow in salt water and salt marshes, and The Tropophytes which are mesophytic in habit for a part of the year and xerophytic in habit for the remainder. Soil. — The majority of plants with which we are familiar grow in the soil, but we must not forget that a great number of NITROGEN OBTAINED FROM THE AIR 129 species of plants live in the water, while others live either para- siticallj or saprophytically on plants and animals. The soil in which plants live must have a suitable texture and must fur- nish certain elements which constitute most of the crude food materials of the plants. Since our agricultural crop plants are dependent upon the soil and since the animals are dependent upon the plants, it is evident that all animal life is dependent upon the soil. If we are to understand plant growth we must know something about the soil in which the plants grow. The various soils are made up of numerous small particles of disintegrated rocks of various kinds, in which is usually mixed more or less decaying or decayed organic materials. The disintegration of the rocks is, due to the freezing of the water which penetrates the minute crevices, to the grinding action of moving masses of ice, to tlie mechanical and solvent action of water and to many other minor influences. Soils are designated as gravel, sand, sandy loam, loam, clay, etc., dependent upon the coarseness or the fineness of the particles of which they are com- posed. The variation in the texture of the soil results in varia- tion in its power to retain water. The most important elements in the soil which either serve as food or influence the growth of plants are phosphorus, potas- sium, calcium, magnesium, sulfur, iron, sodium, chlorine, sili- con, manganese, aluminum and nitrogen. All of these except the last can be found in the ash of the plant and of course must have been taken from the soil by the plant. These elements may be in the soil in proportions too great or too small for the needs of certain plants and satisfactory for others, or may be present, but in such a form as to be unavailable for the plant. Since the difl"erent species of plants are unlike in their requirements we find them more or less in groups dependent to some extent upon the character of the soil in which they grow. Nitrogen Obtained from the Air. — Probably the most im- 130 ECOLOGICAL RELATIONS portant of all the elements is the nitrogen which is essential for all plants and animals. Nitrogen is very abnndant in the air, but the plants cannot make use of it in this free form. However, the air penetrates the soil and its nitrogen is seized upon by certain bacteria and fungi and fixed in the form of nitrates which can be used by the plants. (Chapter X.) This gives us one good reason for keeping the soil in which we are growing plants in loose condition. Nitrogen is also carried down and into the soil by rainfall. The bacteria found in the tubercles of the leguminous plants are the most important organisms in this work. Nitrogen is also obtained from decaying organic mater- ials and thi^ is one reason that humus is so important in agri- cultural lands. Use of Fertilizers. — If the soil does not contain these food elements in the proper proportions or if any of them are unavail- able, the farmer endeavors to overcome its deficiencies by the application of fertilizers, such as stable manure, bone meal, ni- trate of soda, rock phosphate, potash, lime, etc., or by the grow- ing of the leguminous plants or by both. In order to do this to the best advantage it is important that he understand the crop plants to be grown and their food requirements. The elements most likely to be lacking in farm soils are nitrogen (N), phos- phorus (P), potash (K), and sometimes calcium (Ca). Temperature. — This is another factor of plant growth which we very readily recognize and we know that certain fruits such as oranges and bananas grow only in tropical and subtropical countries, and that many other plants are limited in their range by the temperature. In traveling across the country we easily see that forest and prairie sections can be readily divided into smaller areas, such as the pine forest, oak forest, beech forest, etc. We also recognize great belts or areas of agricultural crops, such as the corn belt, cotton belt, wheat belt^ peach belt, etc. On the boundaries of these belts we frequently find these PLANT GEOGRAPHY 131 crops grown with considerable difficulty owing to droughts, frosts and other factors. Light. — This is also an important factor which is very generally recognized. Our attention has been called to the fact that plants turn to the light and that their foliage is ad- justed to receive the light to the best advantage. (Chapter IV.) But a little careful observation will show us that while some plants thrive best in the direct rays of the sun others are always found growing in the shady places. It is now well known that some of our agricultural crops thrive much better in the shade than in the open. Coffee is very generally grown in the shade of larger trees and many plants are grown in an artificial shade produced by slat coverings or by large cheesecloth tents. These and many other factors of nature which influence the spread of plants have given rise to that phase of botany known as Plant Geogi'aphy. PLANT GEOGRAPHY Plant geography is so closely associated with Ecology that it is practically impossible to separate the two subjects by well- defined boundaries. In our early study of geography we learned that the earth was divided into five zones : Arctic, Worth Tem- perate, Torrid, South Temperate and Antarctic, and we soon learned to associate these zones with cold, temperate and hot climates. But a little later we learned that countries in the same parallels of latitudes did not necessarily have the same temperature ; mountainous regions in the torrid zone might be cold as Iceland ; the Gulf current makes England much warmer than points on our Atlantic coast which are much farther south. It is very evident that elevations, moimtains and water barriers and the ocean currents exert very pronounced influences on the temperature of a country and its plant growth. 132 ECOLOGICAL RELATIONS A little later we learned that rainfall was fnlly as important as a climatic factor as temperature and that it had fully as much influence on the character of the vegetation. Probably the greatest rainfall in the United States is over a small area of Gulf coast extending from w^estern Florida to a short distance west of Xew Orleans, a section of the country well adapted to growing rice and sugar cane. The rainfall of most of the southern states is somewhat higher than for the states north of the Ohio River, but cotton has reached its northern boundary far south of the river. The rainfall of the Rocky Mountain Plateau is lower than for any other part of the United States, giving us a great area of country frequently referred to as the American desert. EXERCISES ON PLANT RELATIONS TO SURROUNDINGS 1. Moisture and Germination. — -Fill two small flower pots with soil of tlie same kind, put into an oven until thoroughly dry, allow to cool, plant seeds in botli, add a definite amount of water to one from time to time, keep the other dry, and keep both in a warm, well-lighted place. Note the germination and growth. 2. Growth in DifTerent Soils. — Fill several small flower pots with different kinds of soils and sand, plant with seeds of the same kind, give the same amount of water to each at definite intervals, keep in a warm, well-liglitod place. Note time of germination and rate of growth. o. Influence of Sand on Rate of Growth.— Take a supply of rich, loamy soil and a supply of clean sand, fill one flower pot with the soil, a second with three parts soil plus one part sand, a third witli two parts soil and tAvo parts sand, a fourth with one part soil plus three parts sand and a fifth with pure sand. Plant the same kind of seeds in all, give the same amount of water from time to time, and keep in a warm, well-lighted placp. Note the time of germination and rate of growth. 4. Temperature Affects Growth.— Fill two pots with the same kind of good, rich soil and plant with same kind of seeds. Give the same amount of water and keep each in a well-liglitod place, but keep one in a warm place (70 degrees F. or more) and the other in a cold place (af)out 40 degrees F. or less). Note tlie rate of growth. 5. Effect of Light on Germination and Growth.— Fill two flower pots witli the s;inu- kind of good, ricli soil, i)huit with the same kind of QUESTIONS 133 seeds, give the same amount of water from time to time, keep in a warm room, but keep one in the light and one in the dark ( closet or box ) . Note the time of germination and rate of growth. QUESTIONS 1. Name the four most important factors in plant growth. 2. Tell of the importance of water in plants. 3. What are the hydropliytos? Give examples. 4. What are the mesophytes? Give examples. 5. What are the xerophytes? Give examples. 6. What are the halophytes? 7. What are the tropophytes? 8. How may plants olitain the nitrogen found in air? 9. What elements arc likely to be deficient in some soils? 10. How does temperature att'ect growth of plants? 11. Tell of the influence of light on plant growth. 12. Make a list of plants that thrive in partial shade. 13. Make a list of common food plants and tell in what part of the United States or of the world they are grown. 14. Same for common fibre plants, ^^'hy are thoy not grown over wider ranges of country? 15. What are some of the geographic influences governing the plant life of a region? CHAPTER XIII FORESTRY The study of forestry is a branch of botany that has attracted a great deal of attention in recent years. When America was explored and settled by white men, millions of acres were cov- ered with virgin forest. The land was more valuable for culti- vation than the forest was for any use that the settlers could make of it. Therefore, enormous quantities of these wonder- ful forests were cut and burned in the course of settlement. But with the increasing population and decreasing forests, lum- ber and wood became more and more valuable, until the United States Government found it necessary to set aside large areas of land as forest reserves. These conditions naturally led to the study of forestry, a subject which involves the planting and care of forests and proper protection and economic handling of our natural forest products and the planting and care of shade trees. (Fig. 85.) Many woodland areas have been denuded which are of little or no value for other crops. (Fig. 86.) The United States Government and the various state governments employ a large number of professional foresters for this work, and many cities employ foresters to attend to the planting and care of shade trees. Foresti-y is now recognized as one of the most important studies in our large institutions of learning. The principles of forestry are alsoi practiced on many individual farms throughout the land. Although we cannot take a course of forestry in connection with this brief course in botany, we can learn something of the life of the individual trees of which the forest is composed and some general principles of tree growth. 134 TREE CHARACTERISTICS 135 Tree Characteristics. — Trees are not only the largest plants, but they are extremely complex and highly developed. How- ever, each tree mnst arise from a single cell, in exactly the same manner as any other plant, and is subject to exactly the same laws of plant growth as any other plant. A tree is a woody Fig. 85. — Modern forestry methods provide for perpetual crops of lumber and other forest products. Forest beetles are held in check by burning the twigs after each harvest. (U. S. D. A.) plant with a single stem or trunk which may be straight with many side branches or the trunk may divide into subdivisions. It has a well-developed root system which gives it firmness and by which it secures water and mineral foods. It has leaves of size, shape and arrangement peculiar to its species. The flowers of some trees are large and showy while those of others are so small and inconspicuous that many people never see them and 136 FORESTRY believe that certain species of trees never produce flowers. The fruits are of various kinds and will repay you for careful study. Trees have definite forms which are characteristic of their species ; some trees are low with round dense heads, as the Nor- way maples, others are tall and open as the elm and plane-tree ; some have a single straight shaft as the pine and hickory, while in others the main trnnk branches in such a manner as to lose its identity in several subordinate branches. Fia. 86. — Denuded of forest growth by ruthless cutting and fires. A barren rocky waste ie left, unsuited to other agricultural crops. (U. S. D. A.) Tree Foods. — The tree uses the same kind of food and secures it in the same manner as any other plant (Chapter X), and the amount of energy recjuired in securing the raw food, transferring it throughout the plant, and making it into ma- terial of its own is far greater than we can appreciate. Wood is composed primarily of carbon, oxygen and hydrogen. When absolutely dry about one-half its weight is carbon. We have already studied the processes and results obtained in burning M'ood. (Chapter TX.) TREES PRODUCE GREAT NUMBERS OF SEEDS 137 Tree Growths, — We have already learned something of growth (Chapter X) and know the part played by the cam- hium. When we think of the growing tree, we must think of the thin cambium in not only the trunk but in every branch and twig, and in every root and rootlet. (Chapter VI 11. ) When an annular ring is once formed, its position in the tree is never changed, but new annular rings will be formed, each outside of the preceding one. In most trees the inner wood becomes darker and harder with age and is known as the heart-wood, while the outer which is softer and lighter in color is known as the sap-wood. The passage of water through the heart-wood is checked, but it continues to pass through the sap-wood during the life of the tree. As the tree grows, the amount of heart- wood increases by continual additions from the cambium. Tis- sues of different w^oods have peculiar characters by which stiidents can readily recognize them. Conditions of Growth. — Diiferent species of trees require different conditions for their growth. Some grow in cold climates, others in wrywl climates ; some in dry soils, and others in swamps ; some require certain kinds of soil and light exposure. Natural forests are seldom of a single species but of several species which live and grow under the same or similar condi- tions. Under natural conditions there is a continual struggle between the trees for food, water, and light, and many trees die because other trees near them are more vigorous. Trees produce great numbers of seeds, but very few of these seeds produce trees. M'any of them fall in places where the soil, water or light requirements are unsuited to their existence, or are destroyed by man or some of the lower animals. How- ever, some of them grow where they fall and some of them are carried for long distances, grow and may be the beginning of a new forest area. Some young trees are more vigorous than others of the same kind, grow faster, overtop tliom and shut 138 FORESTRY oli" the light and eventually starve them to death. A few are able to grow beneath the shade of others. [Sometimes a forest is so dense that it is difficult for young trees of the same species as the forest to get a start, but other trees of a different species and with different light requirements may become established. Forest Enemies. — The forest has many enemies ; the most destructive is man who may lumber it with gi-eat waste, or use it for grazing with great losses to the young growth, or care- lessly set fires by which large areas are destroyed. Insects, fungi, wind storms and snow storms also take heavy toll from these natural resources. EXERCISES ON FORESTRY 1. Learn the names of as many trees as possible on your street, in your town, in the park or in a near-by forest tract. 2. Collect flowers, seeds and leaves of as many trees as possible. •'5. Forms of Trees. — ^lake a diagram showing the peculiar branch- ing and form of the common trees. 4. Tree Differences. — Make studies in the woods or elsewhere and report on what kinds of trees in your vicinity are the tallest and what kinds are the shortest, what ones make the densest shade, what ones en- dure shade, what are rapid growers and what are slow growers ? 5. Study blocks of different kinds of wood and learn to recognize them. Carpenters and other wood workers can help you in this study. 0. Close and Open Plantings- — Compare the sliapes of trees of any species in dense plantings with the same in open places. Explain. QUESTIONS 1. What useb are made of the lumber trees in your community? 2. What fruit - producing trees are found in the forests of your community? 3. What nut-producing trees are found in the forests of your com- munity ? CHAPTER XIV PLANT DISEASES Plants are subject to diseases whicli are similar in cause and character to those of the animal, except that the majority of animal diseases are caused by bacteria, while the majority of plant diseases are caused by fungi. A healthy plant is one in which all the parts are perform- ing their regular functions ; a plant which is growing and pro- ducing fruit in the regular manner. A disease is any condition which interferes with the regular functions of the plant or causes its death. Anything that interferes with the taking of food materials of any kind, with photosynthesis, with the movements of plant fluids, with transpiration, with reproduction or with any other function of the plant is the cause of disease. The disease itself is frequently designated by the name of the causal organism. Two Groups of Diseases. — Diseases may be conveniently grouped into organic and environmental: Organic (caused by organisms) Fungi Flowering plants Mites Bacteria Insects Nematodes Slime moulds Environmental (caused by surrounding influences) Soil Temperature Smoke Moisture Gas Chemical (near factories) Some Symptoms of Disease. — A disease may cause (a) dis- colo7"ation of the foliage or other parts of the plant; (&) new or excessive growth ; (c) wilting; {d) unnatural sliedding of parts ; 139 140 PLANT DISEASES (e) foliage spots; (/) perforation of foliage; (g) variegation of foliage; (h) dying of leaves and twigs; (i) dwarfing or atrophy of parts; {j) development of distorted or abnormal growths, such as witches broom, galls, corky out-growths, etc. ; (k) cankers; (Z) increase in size or modification of parts; (m) curling of foliage and formation of rosettes; (ri) hairy roots; (o) exudation (gums, resins) ; (/>) sun burns; (q) rot of fruits, stems or roots. The most noticeable diseases of plants are the rots of fruits and stems which are usually caused by fungi and bacteria ; blights of the leaves, stems, flowers and fruits, which are also caused by bacteria and fungi ; spots on leaves and fruits, which are caused by both fungi and bacteria ; mildeivs, which are white powdery fungous growths on leaves, twigs and fruits ; smuts and rusts, which are fungous diseases of grains and other plants ; cankers, which may be due to fungi or other causes ; yellowings, mosaics, and other discolorations, which may be due to any one of many causes. Wilts, — When the disease injures or destroys the root sys- tem, the food and water supply from soil is reduced or cut off and the plant is either weakened or killed. Diseases of the stem may have the same effect. Diseases of the foliage may interfere with the absorption of carbon dioxide, the transpira- tion of water and the photosynthesis of the plant. The wilt diseases are usually due to fungi or bacteria which live in the tracheary tissue of the fibro-vascular bundles and thus interfere with the rise of water. These diseases are especially injurious on herbaceous plants. The fact that the organisms live within the plant make it impossible to treat by means of spray- ing. Many of these wilt organisms live in the soil from year to year and cannot be controlled except by crop rotatioii in which it is necessary to use crops which are not subject to the disease in question. ROOT DISEASES 141 Root Diseases. — The crown gall (Fig. 87) is one of the very common diseases of onr fniit and other trees, roses, berries and many other plants. It is cansed by bacteria and appears as abnormal c;rowths on the roots and sometimes on the trunk and Fig. 87. — Young tree with crown gall. branches. In some cases it does bnt little harm, but in, other cases it reduces the vitality of the plants and in extreme cases causes death. The so-called hairy root of the apple, pear and quince is caused by the same organism. The roots of these dis- 142 PLANT DISEASES eased trees are covered with numerous small roots which are usually associated with small galls. There is no known treat- ment for this disease. Diseased trees should not be planted. Galls or knots on the roots of plants may be due to other causes. Among the most common are the galls on the roots of apples and grapes which are caused by insects ; abnormal growths Fig. 88. — Leaf spot disease of the pear. on the roots of cabbage and related plants due to slime moulds ; and knots on many plants due to minute worms (nematodes). These and many other diseases of the root systems of plants in- terfere with nutrition, dwarf the plants, reduce the crop and frequently cause death. The leaf diseases are mostly due to fungi which cause leaf spots, leaf curls, blights, wilting, dying and droppings. One of THE DISEASES OF THE FRUITS 143 the most noticeable of these diseases is the leaf curl of the peach which is a fungous disease occurring in the spring and causing the leaves to curl, turn yellow or pinkish and finally drop. In severe cases practically all the leaves fall. The tree puts out new foliage but drops the fruit. The disease when once estab- lished persists from year to year. It can be controlled by proper spraying. The many leaf spot diseases (Fig. 88) reduce the amount of leaf surface and thus reduce the amount of work which the ' Fig. 89. — One of the apple rots, called "bitter rot." plant is capable of doing. Therefore, severe leaf injury will usually result in reduced vitality and reduced yield. The diseases of the trunks of trees usually start with wounds through which fungi gain entrance and cause heart rots. Spe- cial care should be taken to protect street, shade and ornamental trees against such injury. Tree wounds should be painted. The filling of tree cavities is very satisfactory if well done. The diseases of the fruits may appear as deformities, spot- tings and rots. (Figs. 89 and 00.) The great majority of these diseases are due to fungi. If you will examine the rots on a number of apples of various kinds you will be able to throw 144 PLANT DISEASES them into several groups. These diseases are especially severe on fleshy fruits, such as apples, pears, peaches, plums, cherries, tomatoes and many other plants. Many of these diseases can be held in check by the proper spray treatment. The diseases of the grain crops are very destructive and are the causes of heavy losses. The most conspicuous and most im- ■■ ' - i ^^™g^ WB^^^ v---^ ^^^w^^w - ^H mf^, ^ i^.^- ^^^nB>^''- xi^^iflLJ Bi^ ^^^^^S.. ''"^ ' 'M ^^^^^BL_d^ ■ ^■^' ^ ^^^^^H ^^ portant of these diseases are the rusts and smuts (Fig. 91) which are fungous growths in and on the plants. But there are many other less prominent diseases of the grain plants which are very destructive. The study of plant diseases is a study in itself, a well-defined branch of botany known as Plant Pathology. Most of the Agri- cultural Experiment Stations, of which there is at least one in each state, employ one or more plant pathologists who should be consulted by the growers of crops. THE STUDY OF PLANT DISEASES 145 10 Fig. 91. — Smut disease of oats. Healthy oats at ri>;lit. 146 PLANT DISEASES The control of plant diseases depends on the cause and char- acter of the disease in question. In some cases the diseases are carried on the seed and can be controlled by seed selection and seed treatment ; some diseases are carried on nursery stock which should be subjected to careful insjDection for the elimination of both diseases and insect pests ; some diseases persist in the soil and can be controlled by crop rotation and soil sterilization ; and other diseases are controlled by spraying. Advice concerning the character and treatment of diseases of plants can be obtained by writing directly to the Agricultural Experiment Station of your state. EXERCISES WITH PLANT DISEASES. 1. Collections Showing Diseases. — Examine a large number of plants and make oollcotions of diseased plants or parts of plants. 2. Inoculating Soiind Apples. — Select a few sound apples, wash in 5 per cent formaldehyde, then in sterilized water, and put them in two or more closed glass dishes that have been treated in the same manner. Set one or more aside for comparison. Puncture the apples in the other with a sterilized needle or sharp pointed knife and insert a minute fragment of the rotten part of another apple. Observe from day to day and report results. 3. Examine apples kept in this manner for gigng of formation of spores. It may be necessary to keep them under observation for a month or more. 4. Potato Diseases. — These experiments may be duplicated with potatoes and other plants. 5. Make a list of diseases as a result of your own observation. QUESTIONS 1. What do you understand by "plant diseases" ? 2. Enumerate the common symptoms of disease. 3. To what causes are these due? 4. Explain a common cause of wilt. 5. Descrilje the crown or root gall and its effect. 6. What are the chief forms of leaf diseases? 7. Name some common plant diseases which you know. CHAPTER XV PLANT BREEDING This verv important branch of botany which is attracting so much attention at the present time and which is so often referred to as a new subject, no doubt began with the earliest dawn of civilization. Man selected and cultivated the plants best suited to his purpose and the excellent qualities of many of our economic plants are no doubt largely due to plant selec- tions conducted by many generations who did not fully appre- ciate just what they were doing. Plant breeding is based on three laws of plant growth: variation, mutation and hyhridization. (Fig. 02.) Variation is that law of nature which leads to differences of more or less importance among plants of the same species. Many thousands of plants of a species may appear to be the same, but a close examination will show that no two are exactly the same. By selecting seed from the individual plants which possess the desired characters through a number of generations it is frequently possible to emphasize these important charac- ters. In the beginning of the sugar-beet industry in America, the plants yielded about seven per cent sugar, but by careful selection we now grow crops that yield double this amount. Many of our most important varieties of fruits, vegetables and grains are the results of more or less careful selection through many generations. Mutation is the law by which plants produce new species with well-defined characters in a single generation. The per- centage of new species is very small and yet of sufficient im- portance to be of considerable value in agriculture. The study 147 148 PLANT BREEDING of mutation is so ne\v_ that we do not know how mnch we are indebted to it for valuable economic plants. Some of our valu- able plants which we have considered the results of selection niav r(\i]ly be the results of mutation. Hybridization is the production of new varieties (hybrids) by the cross fertilization of more or less closely related species. This process no doubt occurs to some extent in nature, but man has taken advantage of the possibilities of this method of secur- ing new and valuable varieties and many men are now devoting their time to this very important line of work. The method is Fig. 92. — In croesing different varieties of wheat the stamens are removed before they shed their pollen. Tlie pistils are impregnated with pollen brought by a soft brusti troui another variety. The head is then covered with a paper bag and properly labeled. tU.S.D.A.) not difficult but I'equires care, time and patience. The pollen can be readily collected in a watch glass or other small receptacle and then applied to the stigmas of the flowers of the other plants with a delicate camel's hair brnsh. The stamens of the opening flowers should be removed, the pollen applied to the stigma and the blossom then protected against accidental pollination from other sources by covering with a paper bag. (Frontispiece.) After a few days the bag can be removed and a tag fastened to the shoot. In growing annual plants, the results of cross breed- ing can be determined in a comparatively short time, but in the cross-breeding perennials the time will be much longer unless QUESTIONS 149 the seedlings are gi'iifted into niatnre trees and bronght to frnit in a short time. Selection.- — Of course, it will be readily seen that in breed- ing plants that will not hybridize or that do not produce seeds, we must depend entirely on selection. In fact, selection was the most important factor in plant improvement nntil recent years and is now a method that can be used with great advan- tage. Most farmers, fruit growers and gardeners can select their best plants for seed purposes with great advantage to themselves. EXERCISES IN POLLINATION 1. Removal of Stamens. — Select several flowers of tomato or other plants just ready to open. Ivemove the stamen and cover with paper bags. Examine in a week or ten days. 2. Artificial Pollinating. — Select another lot of flowers, remove the stamens, toucli the pistil with open stamens from anotlier flower of the same kind. Examine in a Meek or ten days. 3. Pollination in Greenhouses. — Visit some local greenhouse in which the tomatoes, cucumbers and other vegetables are grown and see how pollination is managed. QUESTIONS 1. How are common plants pollinated? 2. ^Vhat insects are important in pollinating plants? .3. ISIake a list of crops pollinated by insects. 4. Make a list of crops pollinated by wind. CHAPTER XVI WEEDS It has been said that a " weed is a plant growing in the wrong place." There is much truth in this statement for many well-known plants are pests or valuable products, depending upon their location. The morning-glory is a beautiful orna- mental plant in the home grounds but a pest in our cultivated fields ; and mustard is a useful plant which becomes a pest when the farm lands are thoroughly infested with it. Many of our valuable cultivated crops were at one time wild plants of the plains and forest which man has found to be use- ful and has learned to cultivate in an advantageous manner. In fact, if we would go far enough back in, the history of man- kind, back to the time when man was uncivilized, we should no doubt find that all plants were at one time wild or unculti- vated. With the progress of the human race man has learned to cultivate and make use of many plants, but never in all his- tory has man put forth so much effort to conquer nature and utilize her products as at present. Every year sees plants that we have in the past looked upon as weeds brought under culti- vation and every year our government's traveling specialists are collecting both cultivated and uncultivated plants from abroad, many of them from the remote comers of the earth, and sending them to America to be tested in order that their value as farm crops can be determined. Weed Defined. — A weed is not only a plant growing in the wrong place, but it may be a plant which we have not yet learned to make use of, or one which we have not learned to cultivate profitably. However, for our purpose, a weed is a plant which 150 NEW WEEDS INTRODUCED 151 interferes with the growing of the crop in which wc are inter- ested. It may be a vahuible crop if grown separately, but wc do not want it to interfere with the crop under cultivation. The weed may be an excellent crop in one part of the world and a pest in another part. The value of the plant depends upon the use we can make of it and the ease and profit with which it can be grown. How Weeds are Injurious. — Weeds are injurious for many reasons. (1) They take a certain amount of the food and water which the crop plant should have for its growth. The farmer cannot afford to have his crop plants weakened and the amount of the harvest reduced, by the weeds and he cannot afford to buy fertilizers to feed useless plants. (2) Weeds may prove injurious to the crop by shading and if too numerous may completely choke out the crop plants. (3) The weeds may harbor certain insects and fungi which attack the crops. (4) Thistles, nettles, and other thorny or prickly plants may interfere with using the growing crop for pasture or interfere with tillage. (5) Weeds in the meadow reduce the feed value of hay. (6) The presence of weed seeds in the harvest crop may reduce its value. (Figs. 93 and 94.) Weeds Sometimes Useful. — It is sometimes said that weeds are useful, especially on unused lands, because they serve as a cover and prevent the escape of nitrogen and can be plowed under and thus used as a fertilizer. This is an old idea that has come to us from the time when the land was rested by being- left uncultivated for a period of one or more years. But we now know that in most cases it is much better to use a good agricultural cover crop. Rye, certain clovers, vetches and other plants are much more valuable than a miscellaneous lot of weeds. New Weeds Introduced. — Wlien a new country is settled and brought under cultivation we find certain native weeds, 152 WEEDS Fig. 93. — Some conniion weeds. Left to right: Jimson, ragweed, lamb's quarter, joint- weed, rough pigweed. Flo. 94. — Some eommon grasses. Left to right; crabgrass, two barnyard grasses, tw6 of foxtail, panicum, fescue. PREVENT INTRODUCTION 153 Fio. 95. — Crop seeds: 1, red clover; 2, alfalfa; 3, alsike clover; 4, sweet clover; 5, timothy; 6, red top; 7, Kentucky blue grass; S, sU'eet vernal crass; 9, annual rye grass; 10, tall meadow oat grass; 11, English rye grass; 12, orchard grass; 13, broom corn millet; 14, Hungarian millet; 15, German millet. 154 WEEDS some of which disappear rather rapidly, while others appear to thrive as a result of cultivation, and are a continual source of annoyance. But the number of different kinds of weeds will increase. Man will naturally introduce the grains, grasses, clovers and vegetables that he believes can be grown advantage- ously and more or less weed seeds will be introduced with them. Some of these w^eeds will gTow for a single season and die while others will persist from year to year. Other weed seeds will be carried with nursery stock and on the feet and in the hair of live stock, in bedding for live stock, in feeds and in packing materials and in many other ways. In many local- ities stable manure is shipped from the cities to the farms and since the animals from which it is secured may have been fed on imported feeds and bedded with materials brought from a considerable distance we can easily understand how great quan- tities of weed seeds can be introduced. Fighting Weeds. — Every grower of farm crops must make a continuous fight against weed pests. In doing this there are two general methods to follow: (1) Prevent the introduction of the weeds not already present on the farm, and (2) the destruc- tion of those that are present. Prevent Introduction. — The introduction of many weed pests can be prevented by using nothing but clean seeds. Many seeds, especially clover and grass seeds, frequently carry many weed seeds. The examination of an ounce or more of such seed will frequently reveal the presence of many seeds of trou- blesome weeds. Unfortunately, the seeds of some plants are so similar to certain clover and alfalfa seeds that they cannot be detected by persons unfamiliar with their minor character- istics. The Federal government and most of the State gov- ernments employ seed analysts who make examination of sam- ples which are sent to them. Home-grown seed should be just as carefully examined as seeds that are purchased on the mar- ket. (Figs. 95 and 96.) Fig. 96.— Weed seeds: 1, Night-flowering catchfly (Silene erectifolia) ; 2, Sheep's sorrel (Rumex acetosella) ; 3, Curled dock {Humcx crispus); 4, Pennsylvania sniartweed (Polygonum pennsylvanicum); 5, Lamb's quarter {Chenopodiuvi album); 6, Tumbling pigweed {Ama- ranthus retroflexus) ; 7, Peppergrass (Lepidium virginicum) ; 8, Field cress (Lepidium cam- pestre); 9, Yellow trefoil (Medicago lupulina); 10, Evening primrose {Onagra biennis); 11, Wild carrot (Daucus carota); 12, Rugel's plantain (Flantago Rugelii); 13, Huckhorn (Flan- tayo lanceolate); 14, Ox-eye daisy {Chrysanthemum leucatithemum) ; 15, Canada thistle (CnicUs arvensis); 16, Bull thistle (Cnicus lanceolatus); 17, Yarrow {Achillea millefolium); 18, Dan- delion {Taraxacum officinale); A, ventral side; B, dorsal side. 1, Caryophyllacea?; 2-4, Polygnacese; 5, Chenopodiacese; 6, Amaranthacese; 7-8, Cruciferae; 9, Leguniinosae; 10, Anagracea;; 11, Umbellifera;; 12-13, Plantaginaceae; 14-18, Compositse. 156 WEEDS Straw aud similar material wliicli has been used for pack- ing and is likely to contain weed seeds should be burned or rotted in compost to kill seeds. Stock bedding and feeds, should be produced on the farm whenever possible, instead of pur- chased from a distance. Eradication.— The fight against weeds already on the farm will depend upon many conditions. Many weeds can be erad- icated by sowing a crop which requires close cultivation ; others by the use of smother crops ; others by the repeated sowing of a quick-growing crop which can be pastured with sheep. The success of these and other treatments will depend in some measure on the training of the farmer. It will be readily seen that the methods used against aimuals, biennials, and per- ennials must necessarily vary. Therefore, the greater the famil- iarity with the life history of the pest, the gi-eater are the possi- bilities for success. Perennial weeds will thrive best in fields where they are least disturbed, as in pastures and hayfields. When such w^eeds are gaining too strong a hold, many of them may be destroyed by plowing the field and using it for cultivated crops for a few years. Potatoes, corn, and other summer crops may be used, but they should be well cultivated. Annual weeds are often very bad in grain fields or in corn and other cultivated fields. They may be choked to some extent by sowing the field very densely with grass for hay or pasture. EXERCISES RELATING TO WEEDS 1. Make a collection of the noxious weeds of your neighborhood. 2. Corn-field Weeds. — ■ Which ones of these are most commonly found in cultivated fields? 3. Pasture Weeds. — ^lake a list of the weeds most common in the pastures of tlie vicinity. 4. In Grain Fields. — If possible, examine a field of wlieat or other small grain, either while the grain is growing or after it is cut. Make lists of the weeds growing in the grain or in the field after harvest. QUESTIONS 157 5. Examining Seed Samples. — Cct samples of clover seeds, and other small seeds. Examine eacli sample for (a) weed seeds; (b) dead seeds; (c) foreign inert matter or grit; {d) sound seeds true to the variety; (e) others of useful varieties. Count the number in each of these five classes and then determine the percentage of each. 6. Numbers of Weeds. — Search the fields, fence rows, road sides and other places for dense growths of weeds. Bend a wire into a circle or use a barrel hoop and throw it over the densest cluster you can find, count the number of weeds in the circle. Determine the number in a square foot and calculate the number per acre (43,560 sq. ft.). Do likewise for several diHerent species of weeds. 7. Study the smothering influence of weeds found growing in rows of young garden crops, corn, etc. QUESTIONS 1. What is a weed? 2. In what ways are weeds injurious? 3. How are weeds introduced into new localities? 4. Have you seen instances of these? 5. How can a farmer prevent the introduction of weeds? 6. How may perennial weeds be most easily eradicated? 7. How may annual weeds be eradicated? CHAPTER XVII PTERIDOPHYTES We have studied that group of plants and the subdivisions (the seed-bearing phmts) which you may consider the most important and we have learned that there are three other great groups. (Chapter V.) Although these groups furnish us com- paratively little in the way of food, clothing and building ma- terials, yet they are of great interest and of considerable value to man. To the botanist they are esj^ecially interesting because we cannot get a thorough knowledge of the plant kingdom with- out studying them. They are of value to all of us because many plants belonging to these groups are of commercial value. There- fore, let us consider the next highest group, the Pteridophytes, which includes the ferns and the related plants. True Ferns. — The largest and most familiar group is the order Filicales or true ferns. (Fig. 97.) These plants have true roots, stems and leaves, but the structure of the stems is quite diiferent from anything we have studied. The stems may be short and erect or creeping, underground type known as rhizomes, giving rise to many roots and to the masses of green foliage with which we are familiar. But in tropical countries we frequently find the beautiful tree ferns with their very large trunks. If we cut a cross-section of a stem and examine it under a compound microscope we find a well-developed fibro-vascular system composed of practically the same tissues as in the higher plants but arranged quite differently. The wood cells are in the centre surrounded by the bast cells which are in turn sur- rounded by an endodermis. This is known as the concentric arrangement. These bundles are weak as compared with bun- 158 FRUIT DOTS 159 dies of the spermatopliytes, but the stem is streng-thened by the masses of schlereiichymti tissue which can be readily seen. The leaves or fronds, as they are usually called, are very similar in structure to the leaves of the Angiosperm. In fact, the similarity is so striking that it is not necessary to describe it at this time, but the student will do well to make a careful study and comparison of the leaf with that of the Angiosperm. Fiu. 97. — A fern glade. (Chapter IV.) However, the leaves tend to unroll in a ]>einiliar manner (Fig. 98) which can be readily seen and which is char- acteristic of the ferns. Fruit Dots. — On the under surfaces of many of the older leaves will be found numerous fruit dots or sori (singular sorus). (Fig. 99 and 100.) They vary greatly in size, character and arrangement in the different species of ferns and in most cases are covered with a delicate membrane known as the indusium. 160 PTERIDOPHYTES (Fig. 100.) These dots contain niunerous sporangia (singular sporangium) (Fig. 101), which are filled with spores. Each sporangium is supported by a stalk and from a side view appears to be flat, but as a matter of fact is slightly thicker in the centre than on the margin. The marginal cells are highly specialized and are of two kinds ; the thick-walled cells from about three- fourths of the distance and the thin-walled cells for the re- mainder of the distance. When the spores (Fig. 102) are mature, the drying out of the sporangia results in an uneven Fig. 100. Fig. 101. Fig. 102. Fig. 98. — Young fern leaf showing method of unrolling. V Fio. 99. — Part of fern leaf showing sori or fruit clusters. Fig. 100. — Part of fern leaf showing sori with indusium. Fig. 101. — Sporangium from fern sorus. Fig. 102. — Fern spores from sporangium. tesnsion of the two kinds of cells, a bursting of the sporangium and a scattering of the spores. Two Steps in Reproduction. — The spores germinate and eventually form what is known as ihe protlialUum. (Fig. 103, e.) In most ferns this prothallium is very small and somewhat heartshaped. It is composed of chlorophyll bearing paren- chyma cells and has many rhizoids which are very similar to the root-hairs of the higher plants. They penetrate the moist soil from which they derive both water and food in the same man- ner as root-hairs. On the under surface will be found numerous small bodies, the archegonia (singular archegonium) and the HORSE TAILS 161 antheridia (singular antheridmm). In some ferns they are borne on the same prothalhis while on others they are borne on different prothallia. The Archegonia (Fig. 103, V) are borne near the notch of the prothallus, and somewhat flask-shaped with the base imbed- ded in the tissues and the neck extending downward and slightly curved. An examination with the compound microscope shows a large egg (ovum) or female) cell (Fig. 103, c") in the large part and a row of canal cells in the neck. These canal cells become gelatinous or semi-fluid in character. The Antheridia (Fig. 103, h') are spherical and produce great numbers of minute, unicellular, spiral, free swimming Iwdies known as sperms or male cells. (Fig. 103, c'.) The sperm cells swim in the moisture oil the surface of the prothallia and the soil, and some few eventually reach the archegonia, enter the canal and one unites with each ovum or egg cell. This is known as fertilization. It corresponds to the fertilization of the egg in tlie embryo sac of the Angiospemi. (Chapter VI.) As a result of this fertilization, cell division occurs and the egg grows into a fully developed fern. (Fig. 103, e^ /.) With the development of the fern, the prothallus, upon which it at first feeds, is gradually destroyed. Horse Tails. — There are many other fern-like plants which we will find quite interesting if we have time to study them. Among the most common are the horse-tails or scouring rushes (Equisetum). The aerial stems are derived from an under- ground stem and may be branched or unbranched, hollow jointed, fluted with well-marked longitudinal ridges and furrows and infiltrated with silica which makes them rough and rigid. The branches and modified leaves are always in whorls and at the nodes. At each node the stem is surrounded with membran- ous sheaths which correspond to the leaves of higher plants. A cone-shaped fruiting structure is borne at the apex of the stem 11 162 PTERIDOPHYTES and is composed of modified leaves or Sporophylls, bearing small sacs or sporangia containing the spores. The spores have four spiral rings which straighten out when dry and roll up when wet and thus cause the spore to move over short distances. The Fig. 103. — Diagrammatic representation of the life history of the fern: a, prothallium; b', antheridium; b", archegonium; c', sperm; c", ovum; d, oospore; e, prothallus and young fern; f , mature fern showing under-ground stem, root and leaf bearing sori ; g, sporangium ; h, spores. life history of the horse tail is practically the same as that of the true fern. Other Fern-like Plants. — The so-called club mosses or ground pines, the selaginellas and the quillwort are groups of small plants which have life histories very similar to that of the true ferns. The greatest value of the ferns at the present time lies in their great beauty for decorations of various kinds and we must EXERCISES WITH PTERIDOPHYTES 163. not forget that the growing of ferns is an industry representing many thousands of dollars. In past ages tlie ferns were much more ahundant and much larger than at the present time and we are indebted to them, to some extent, for the enormous beds of coal from which we secure most of our supply of fuel. ( Chap- ter^ IX and XVIII.) EXERCISES WIT« PTERIDOPHYTES 1. Examine a fern carefully and note its roots, stem, leaves, sori and indusium. 2. Cut cross-sections of the stem and examine under a compound microscope and note the points referred to in the text. Material for this purpose can be preserved in alcohol or formaldehyde. 3. Study the leaf in the same manner as indicated for leaf of the Angiosperm. (Chapter IV.) 4. Remove a sorus, crush and examine under the compound micros- cope. Note the character of the sporangia as referred to in the text. 5. Examine a prothallus with a hand lens or under a low power of tlie compound microscope. Material for this purpose can usually be secured from a neighboring greenhouse. QUESTIONS 1. Where do you find the stems of the fern? 2. Compare the fern stem with tlie stems of a flowering plant. 3. Compare the leaf of a fern with the leaf of a flowering plant. 4. What do you find on the fern leaf not found on the ordinary leaf? Reference. — Read all you can al)out tlie formation of coal-beds. For such information see a good encyclopedia and works on Geology. CHAPTER XVIII BRYOPHYTES We will now study the two great, groups of Bryopliyies, the Musci or mosses and the Hepaticce or liverworts. They are of little value at the present time except for packing material where it is necessary to retain moisture, but in past ages (the Carboniferous Age) they were much more abundant than at any time since and we are indebted to them for the greater part of our enormous beds of coal which we are now using. Mosses, — An ordinary moss plant presents an upright stem with three more or less distinct rows of leaves. A more careful examination will show us that this stem is very weak, that it does not contain a fibro-vascular bundle but is composed of elongated parenchyma cells. We will find also that the leaves are com- posed entirely of parenchyma cells and that their apparent mid- rib is composed of elongated cells. These characteristics very readily convince us that we are studying a very simple type of plant as compared with the Pteridophytes and Spermatophytes. Arising from the top of this plant is a long, slender stem, setea, bearing a capsule which is covered with a cap or calyptra. (Fig. 104, a, h.) If we remove this cap we will find the oper- culum (Fig. 104, c), which is a small cover on the end of the capsule. If we remove the operculum (Fig. 104, e) we will find the peristome or teeth (Fig. 104, c?.) These teeth are very sensi- tive to varj'ing degrees of moisture which causes them to move inward and outward and thus controls the distribution of the spores which are borne within the capsule. These spores will grow and each produce a filamentous prothallus or protonema which gives rise to new moss plants. 164 MOSSES 165 But moss plants also have sexual organs similar to the ferns. Thej are borne in the tops of the leafy plants early in the spring and are known as antheridm and arcliegonia. (Fig, 104, f, g.) The antheridia are club-shaped and have very long necks. The Fig. 104. — a, mature moss plant; b, capsule covered with calyptra; c, capsule without calyptra; d, capsule with operculum removed showing peristome; e, operculum; f, arche- gonium; g, antheridium; h, paraphyses or sterile organ. antheridia and archegonia arc always borne on different plants. The process of fertilization is practically the same as -in the ferns and the fertilized egg grows into the seteee and capsule referred to above. 166 BRYOPHYTES There are two large groups of mosses, the Bryales, which we have just described and the Sphagnales. This hitter group is the characteristic moss of the sphaguum swamps and was the most important group of phmts in the formation of peat and coal beds. The Hepaticae or liverworts are not so familiar to most of us as are the mosses and ferns. They rank next below the mosses and are an extremely interesting group for study, but of very little, if any, economic value. There are several divisions of the hepaticae, but one of the largest and most common forms nit Fig. 105 — Marchantia polymorpha showing two cupules bearing gemmule. Fig. 106. — Surface view of marchantia polymorpha very much magnified. Fig. 107. — a, female plant of marchantia polymorpha bearing two archegonial branches; b, also a single antheridial branch from a male plant. is known as Marchantia polymorpha. (Fig. 105.) It reminds us of the fern prothallus but is much larger and branching. It is thick along its central axis and thin at the edges, lies flat on the wet soil and has many rhizoids. The upper surface is divided into small areas with a small opening (stoma) (Fig. 106) in the centre of each. These small areas give it a super- ficial resemblance to the liver of an animal and therefore the name " liverwort." As the apical part of the plant grows the basal part is gradually dying. Along the upper surface will fre- quently be found saucer-shaped structures containing small buds which are capable of growing into new plants; a non-sexual method of reproduction. THE HEPATICiE OR LIVERWORTS 167 If we examine a cross-section of the tliallus under a com- pound microscope we will find the epidermis covering a large chamber beneath each stomata. Within the chamber are great numbers of delicate chlorophyll bearing parenchyma cells while the lower cells contain little or no chlorophyll. The sexual organs are borne on separate plants. The female c" © c' ©dl / 9' r FiQ. 108. — Diagrammatic representation of the life cycle of Marchantia polymorpha; a', mature male plant; a", mature female plant; b' antheridium; b" archogonium; c', sperm; c", ovum; d, oospore; e, young sporoplyte; f, and f", spores; g', and g", young plants. plants (Fig. 107, a) bear erect stalks supporting radiating struc- tures which resemble the handle and ribs of an umbrella in their arrangement. On the under surface of the radiating parts will be found the minute flask-shaped archegonia. The male plants (Fig. 107, h) l>ear erect stalks supporting disk-shaped Iwdies, on the upper surface of which will be found minute openings into cavities containing the antheridia. The fertilization is the same as in the ferns and mosses. The stalk of the female 168 BRYOPHYTES body elongates and numerous caj)SuJes are produced on the under surface. These capsules contain numerous spores and also some spiral-shaped bodies known as elaters, which burst the capsules and help to distribute the spores. The spores grow and pro- duce new plants. (Fig. 108.) There are many other forms of liverworts, some of which are leafy and resemble moss plants, and are frequently mis- taken for mosses. EXERCISES WITH imYOPTIYT'ES 1. Examine a moss plant and note the cliaracter of its stem and leaves. 2. Examine a fruiting moss plant and note the setea, capsule, and calyptra. Remove the calyptra and examine with a hand lens for the peristome. 3. Examine a non-fruiting plant of the Marchantia poh/mnrpha and note shape, surface area, stomata, and cupules or non-sexual fruit inj; cups. Scrape some of the rhizoids from the under surface and examine under the compound microscope. 4. Cut a cross-section and examine under a compound microscope and note different types of parenchyma cells. 5. Examine the plants which are carrying the fruiting bodies. 6. Crush a capsule and examine under the microscope; note spores and elaters. QUESTIONS 1. To what great group do the mosses and liverworts belong? 2. Describe a true moss plant. 3. Describe the thallus of the liverworts. 4. How and where are the sexual organs of the liverwort borne? How does the fertilization take place? ,5. What are the most striking points learned in your study of Rry- ophytes? CHAPTER XIX THALLOPHYTES We have now come to the lowest great division of the plant kingdom, the Tliallophytes, which are subdivided into three divisions, the Algce, the Fungi and the Bacteria. The second and third of these groups do not contain chlorophyll and are therefore quite different in habit from all other groups of the plant kingdom. The algae vary greatly in both size, structure and color, but all of them contain chlorophyll and are able to do the work of photosynthesis or starch-ni.aking. The range from the small, one-celled plant which cannot be seen without the aid of the microscope, through delicate thread-like forms up to the enor- mous sea-weeds, possessing root-like, stem-like and leaf-like organs. They are widely distributed throughout the world and are of much' greater importance than we might at first suppose. Minute forms are found in great numbers, causing the green stain on the bark of trees and stones and brick walls, in the streams and pools, and in the seas, gulfs and bays and even the broad ocean itself. The types are entirely too numerous to mention in a work of this kind, and therefore, we must content ourselves with a study of two or three of the most common forms. Many of the unicellular forms found in moist places on trees and walls repro- duce by simple division, each division resulting in the forma- tion of two new plants, each similar to the parent. Each plant is capable of performing all the function of a much larger and more complex plant ; i.e., the absorption of water and minerals in solution and of nitrogen, tlie taking in of carbon dioxide, and photosynthesis and reproduction. 169 170 THALLOPHYTES The filamentous forms are composed of single rows of cells, each cell capable of sub-division, and if separated from the others, of producing a new plant. The very common Spirogyra (Fig. 109) is an excellent type for study. The cells are cylin- drical in shape and attached end-to-end. Each cell contains an imier lining of protoplasm and numerous cross strands of the same material ; also a nucleus which may be located in any part of the cell but usually in the centre. The protoplasm and nucleus are transparent and cannot be seen readily without the Fio. 109. — Spriogyra: Fig. 110.— CEdogoniur single cell showing chromatophore and nucleus; b, two plante showing sexual reproduction, a, plant showing non-sexual cells; b, plant showing oogonium and antheridium. use of an artificial stain. The spaces between the strands of protoplasm are known as vacuoles and are filled with water. Embedded in this protoplasm will be readily seen the spiral chrornatophores or chloroplasts containing the chlorophyll. Scat- tered along this chlorophyll will be seen the round shining pyrenoids which are supposed to be the centres for food forma- tion or photosynthesis. The cell of the spirogyra may be looked upon as a typical plant cell in which all the functions of plant life are performed. Spirogyra. — Tf we examine a great many plants of spiro- gyra. we will probably find some specimens which are attached OTHER ALGM 171 two-and-two by means of short tubes, the one plant being male and the other female. The tubes are outgrowths from both plants which tend to unite ; the separating walls are dissolved and the contents of the male cells pass into and unite with the contents of the female cells, forming what is known as zygo- spores, which will eventually i)roduce new plants. Ulothrix is another filamentous form which produces a large number of ciliated free-swimming cells known as zoospores. They swim for a time, come to rest and each grows into a new plant. In some cases these free-swimming cells (gametes) unite in pairs and form zygospores. CEdogonium (Fig. 110) is another filamentous form, a spe- cies which presents a great variation in sexual character. A cell may produce a single large, ciliated cell or zoospore which will swim for a time, attach itself and grow into a new plant. Or, it may produce a large female cell (gamete) w^iicli is retained in the old cell-wall (oogonium) and fertilized by small free-swimming zoospores or sperms (gametes) which are pro- duced by another cell or antheridium. In other species of G^dogonium the oogonia are produced in large female plants and the antheridia in the small male plants. The Vaucheria are filamentous but unicellular and multi- nuclear forms. The non-sexual reproduction is by the formation of a cross wall at the end of a filament, thus forming a cell from which a single large motile or non-motile spore is produced. The sexual reprodiiction is by the formation of oval oogonia, each containing a single large ovum or egg and curved, tubular an- theridium containing many small sperms. The sperm escape and at last one reaches the ovum which is fertilized and results in an oospore or resting spore. This is more nearly like tlie liverworts, mosses and ferns than most of the alga?. Other Algae. — Concerning the many other forms of algrp, wo may briefly say that they are the forests and the i)astiires of 172 THALLOPHYTES the waters and without tlioiii aiiiinal life in the water would be as impossible as animal life on the land without land plants. We may also add that some articles of conmierce, such as iodine, are obtained from the algae, and the time may not be far distant when the enormous beds of seaweeds will prove a valuable source of commercial potash for fertilizers. The fungi are surprisingly like the algse, but differ from them in the fact that they do not possess chlorophyll. There- fore, they are unable to do the work of photosynthesis and must depend primarily upon organic matter, i.e., either dead or living plants or animals, for their food supply. Those which live on dead organic material are saprophytes and tliose which live on living organisms are parasites. We wiU give brief descrip- tions of the most conmion types. The yeast plants {Saccliaromyces) are among, the very sim- plest in structure. They are very minute, spherical, and repro- duce by budding. They are found abundantly in sugary solu- tions and are extremely important in alcoholic fermentations. We are all familiar with their use in the making of bread. Although simple in structure they have a method of reproduc- tion which takes them from the lowest of the fungi. The common bread mould {Rliizopus nigricans) (Fig. Ill) is one of the best known of the lower fungi. It occurs on stale bread kept in damp places and appears as numerous delicate, white threads containing protoplasm, both in the bread and erect on the surface. These threads are called myceliwn, but a single one is often called the hypha. On the tips of the hyphee are numerous spherical sporangia or spore cases containing spores. They become black with age, burst and discharge the spores which are readily carried in the air. The sexual reproduction is by the formation of lateral branches from two filaments. These branches come in contact and swell, a cell-w^all is formed across each and the wall at PARASITIC FUNGI 173 the point of union is dissolved, permitting the union of the contents of the two cells. This results in the formation of the zygospore which is capable of giving rise to a new plant. The sexual method of reproduction rarely occurs in nature. The species of Saprolegnia (Fig. 112) are parasitic on fish, sionally on decaying food. Thread-like filaments of the fungus grow out from the material on which it is living. Cross walls or septa are formed in these filaments and great numbers of Fig. 111. — Ilhizopus nigricans or bread mould; a, entire plant showing sporangia; b, mature zygospore. unicellular, free-swimming zoospores will be produceerries have very little or no pollen. The two types of blossoms, with aud without stamens, arc shown in Fig. 133. Growers are unable to obtain fruit from the imperfect va- 208 IMPORTANT FAMILIES OF PLANTS rieties (not having' pollen) unless those with perfect flowers are grown near thein. The two types may be planted together, with at least one row of a perfect-flowered sort for three or four rows of the imperfect ones, and these nuist be such as blossom at the same season. - ^ ■'^ ^SS^^^ir 'M^ •r'^M^ jftB^^^M^HBrTji^^ '' V^fflWB uSmH^j^F^ w^^^S^^m tL-j^gKS^MKt B^^^^hBBB| _„ .^Ji \ , - -.^ Fig. 132. — Strawberry. The perfect-flowered varieties will produce fruit when planted alone. They are more popular than the others. Two varieties with imperfect flowers are Warfield and Haverland. Crescent and Glen Mary bear very little pollen. Over fifty perfect-flowered varieties are known. Some of these are Dun- lap, Aroma, Gandy and Excelsior. BUDDING OF PEACHES AND PLUMS 209 As the strawberry propagates itself by means of runners which take root at the nodes, the varieties are easily kept pure. The crossing of the pollen does not affect the character of the fruit or the purity of the plants grown from the nmners. Poorly developed fruits, called " nubbins," are often the result of poor pollination. This may be due to one of several causes: (a) frost, (b) hail, (c) rain, (d) spattering of soil on the pistils, (e) insufficient pollen on varieties blooming late in the season. Mulches of straw or other litter will prevent injury from spattering soil during heavy storms. Growing several varieties together will aid in supplying enough vigorous pollen and cause better development of the fruit. Propagation. — Apples, pears, and quinces are poma- ceous fruits and propagated by growing stocks from seeds, thpn VinrlfliSio' nnrl oToffino- ^i^- ^33. — Flowers of strawberriea. men OUaaing ana graiting pi.tiiiate or imperfect at left. Perfect at with the desired varieties. "^^*- (Productive Fam-ing.) The seeds are obtained from the pomace of the cider mills. For many years it was very generally believed that seeds and stocks from France were better than the domestic supply, but in recent years the sentiment has been changing and a very important stock-growing industry has developed in Kansas, Nebraska, Iowa and other states. Blackberries, dewberries and raspberries are usually gro^vn from suckers and root cuttings. jSTew varieties are grown from seed. Budding of Peaches and Plums.— The steps in the method of shield-budding are shown in Fig. 134. The seeds are sprouted in early spring after being mechanically cracked, or broken by freezing in moist soil. Scions are cut from the cun*ent season's growth in August and September, and the buds from these are 14 210 IMPORTANT FAMILIES OF PLANTS inserted under the bark of the young seedlings riglit away. These buds remain dormant until spring. When growth begins the seedling top is pruned away, leaving only the shoot of the good variety. For June budding, dormant buds are gathered in late fall and held until June in wet sawdust in a cold cellar or in other cold storage. The budding is done in June on seedlings started in very early spring. Root Grafting of Apples and Pears. — When trees are to be Fig. 134. — Steps in budding the .stems of seedlings with buds of good varieties. A, the shield-shaped bud and parts cut from any good variety. B, a T-shaped cut made in the bark of the seedling stem. C, the same with bark opened. D, the good bud set in place under bark. E, the wound well wrapped and tied with raffia or waxed cotton. (Productive Farming.) propagated by root gTafts (Fig. 135), tlie tongue-grafting is usually done in the winter. The seedlings of one season's growth are dug in the fall after the leaves are off. They are stored in small bundles in boxes of wet sawdust in a cold cellar. The scions from the desired varieties are gathered about the same time. They are labeled and stored in like manner. The spare hours of winter are used for the work, which should be done in a cool room or cellar. The materials and new grafts must be kept moist and cool during the process. The grafts are then stored in wet sand or sawdust in a cool cellar till dan- GOURD FAMILY 211 ger of severe frost is over in the spring. They are then set in rows in good garden soil. They are planted deep enough to leave only one or two buds above ground. Here they arq grown for a year or more before being transplanted to the orchard. The peach, plum and cherry are drupaceous fruits and are usually propagated by growing stock from seeds and then budding or occasionally grafting. Plums are sometimes grown from suckers. p^ . ■' r\\\ III SAXIFRAGE FAMILY (SAXIFKAGACE.E ) Herbs or shrubs with perfect, reg- ular (occasionally irregular) flowers. Calyx more or less united with the ovary, four to five petals attached to calyx, stamens same number as the petals and alternate with them or two to ten times as many. Ovary more or less inferior. Fruit a two-chambered capsule or true berry. Leaves alter- nate or opposite or whorled. Currant and Gooseberry. — The common red currant {Bihcs ruhruni), the black currants (R. floridum and R. nigrum), the gooseberries (R. grossidaria and R. cynosbate), the American gooseberry (R. hirtellum) and many species and varieties of currants and gooseberries (Fig. 13G) are valuable fruits. They are extensively grown as garden fruits, but the historical records are very imperfect and uncertain. Gooseberries and currants are usually ol>tain0d from hard- wood cuttings, but new varieties are grown from seed. GOURD FAMILY (cUCURBITACE.e) This very important family has monoecious or dicrcious, oc- casionally perfect, usually solitary white or yellow flowers (Fig. Fig. 135. — Steps in making the tongue-graft used in root grafting apples, pears, etc. A and B, root and scion with tongue cut in each. C, the two shoved together and ready to be tied with waxed cotton. (Productive Farming.) 212 IMPORTANT FAMILIES OF PLANTS Fig. 136.— Gooseberry. Fig. 137. — Cucurbit blossom. THE PUMPKIN, GOURD, AND SQUASH 213 137.) Calyx five-cleft and bell-shaped; corolla five-cleft and bell- or wheel-shaped; stamens five, ovary inferior and one to many chambered, developing into a many-seeded true berry fruit. In many species the fruit is large and fleshy and edible. Among the most important are : The cucumber {Cucumis sativus), which is of Asiatic origin and was cultivated about three thousand years before Fig. 13S.— Uibhed type ..f (.-ant .1. the Christian Era. The muskmelon or cantaloupe (C. melo) (Fig. 138), is indigenous to Asia and possibly tO' Africa. It was cultivated by the ancient Egyptians and was known to the early Greeks and Romans. The watermelon (Citrulhis vulgaris) is a native of the torrid regions of Africa, but was cultivated long before the Christian Era. It is now widely distributed throughout the tropical and temperate zones. The pumpkin, gourd, and squash — (CucurhUa melopepo) flat squash, (C verrucosa) warty or long-necked squash, (C. 214 IMPORTANT FAMILIES OF PLANTS maxima) winter or gourd squash, (C*. pepu) pumpkiu — are well-known products of both tropical and temperate climates. The pumpkin is supposed to be of American origin. Fig. 1.39. — The long form of carrot. The members of this family are very generally gi'own from seed and are widely distributed througliout the temperate and tropicar climates. The growing of cucumbers under glass has COFFEE AND QUININE 215 developed into an important industry near many of our large cities. The weed members of this family are of no very great importance. PARSLEY FAMILY (uMBELLIFER^) The family is characterized by five-parted calyx and cor- olla; tvi^o-chambered inferior ovary and umbel inflorescence. Among the most important members are: The celery (Apium graveolens), which is well known. It was used as food by the ancient Egyptians, Greeks and Romans and also as a medicine by the Egyptians. The parsnip (Pastinaca saliva) originated in Europe but is now widely cultivated as a food for man and live stock. The carrot {Daucus carota) (Fig. 139) is a vege^■ table whose history is not known. This family also includes the anise (Pimpinella anisum) ; asafoetida (Ferula narthex) ; coriander (Coriandrum sativum) ; parsley (Carum petroselinum) ; caraway (Carum carui) ; and many other more or less well-known plants, some of which are useful while others are pests. The members of this family are grown from the seed. Cel- ery, parsnips and carrots may be kept in storage for consider- able time. This family also includes a number of weeds which can be kept in control by the use of cultivated crops and also by the use of cowpeas, soy beans or similar smother crops. MADDER FAMILY (rUBIACE.Ts) Coffee and Quinine. — This family includes the coffee {Coffea arahica and C. Uherlca), the quinine plant {Cincliona officinalis) and other plants with interesting histories. (Read the history of these plants in an encyclopedia.) 216 IMPORTANT FAMILIES OF PLANTS SUNFLOWER OK COMPOSITE FAMILY (cOMPOSITyE) This is one of the hirgest families of the flowering plants. It is characterized by nnmerous small flowers growing in a close head. These flowers are either polygamous or monojcious. The ovary is inferior and the calyx tube is attached to it ; the corolla is five cleft, either tnbnlar or strap-shaped ; stamens five, attach- ed to corolla ; anthers united into a tube surrounding the two- cleft style. In most plants the central or disk flowers are Fig. 140. — Sunflower, showing the composite flower head. tubular and the marginal flower strap-shaped, but in some plants all of the flowers are of the same kind. This 'family includes some few plants used for food, such as the Jerusalem artichoke (Helianthus tuherosus L. ), lettuce (Lactuca sativa), some few others that are used in medicines, and a large number that are used for ornamental purposes, such as the sunflower {Helianthus annuus) (Fig. 140), the daisy and chrysanthemum (Chrysanthemum carineum), gold- enrods (Solidagos), asters, dahlias and others. BLUEBERRY, HUCKLEBERRY AND CRANBERRY 217 This family also includes the dandelion (Taraxacum officinale), iron weed {Vernonia), fleabanc and meadow white tap (Erigeron), thistle (Carduus), and many others that are troublesome as weeds. HEATH FAINIILY ( VACCINIACE.e) The flowers of this very interesting family are four to five parted ; calyx attached to am inferior ovary, the petals united ; Fig. 141. — Cranberries. stamens eight to ten ; ovary of several chambers and developing into a true berry. Blueberry, Huckleberry and Cranberry. — The most im- portant plants of this family are the blueberries and huckleber- ries {Gaylussacia) and the cranberries (Oxycoccus) (Fig. 141), both of which are indigenous to America. Cranberry-growing is a highly specialized industry which is 218 IMPORTANT FAMILIES OF PLANTS restricted to very limited, parts of the country. The conditions for success in this line of farming are to be found in very few parts of the country. Old peat bogs with an ample supply oi water are essential. CONVOLVULUS FAMILY (CONVOLVULACE^) The flowers of this family are perfect and terminal ; calyx five-cleft and persistent; corolla, funnel-shaped and five-cleft; stamens five and attached to the corolla. The family contains a large number of ornamental plants of which the morning glory is typical. Many of these plants are so common as to be wTcd pests. Sweet Potato. — The most important economic member of this family is the sweet potato {Ipoma'a batatas). Some au- thorities claim that this plant is Asiatic, while others claim that it is American. It may possibly be indigenous to both continents. It reaches its greatest development in the tropical countries, where it makes a very luxuriant growth and blooms freely, but it is extensively cultivated in the sandy districts of the temperate zones. Certain varieties are cultivated un- der the name of yams, but the true yam belongs to the family Dioscoreacea\ Propagation. — In the temperate zone, sweet potato plants are grow^n from roots which are laid in hot-beds, cold-frames or forcing houses, dependent upon the climatic conditions. The plants are then transferred to the field and are most productive in sandy soil. In tropical countries, the crops are usually grown from cuttings set directly in the field. This family includes a number of very troublesome weeds, which are difficult to eradicate except by the use of cowpeas, soy beans or similar smother crops. This family also includes the dodder or love vine, which we find growing parasitically on many of our flowering plants. POTATO 219 The seeds germinate in the soil, but the vine very soon attaches itself to another plant and loses its connection with the soil, thus becoming strictly parasitic. Some of the dodders are very troublesome weeds. NIGHTSHADE FAMILY (sOLANACEzE) This is one of the most important families in the plant king- dom. The calyx is five-cleft (occasionally four or six) and Fig. 142. — Blossom of egg-plant. Note its similarity to the Irish potato blossom. persistent; corolla five-cleft (sometimes so deeply that the petals appear to be distinct) ; stamens five and attached to the corolla; ovary two- to five-chambered and with many ovules. (Fig. 142.) Fruit varying from a dry pod to a true fleshy berry. The most important members of this family are: The potato (Solanum tuberosum) is indigenous to Chile, Peru and Equador, where it was found growing by the early Spanish explorers. It is now widely distributed throughout the world and is one of our most important food products. The wild potatoes produce small tubers and many seeds, but careful 220 IMPORTANT FAMILIES OF PLANTS selection has given us many varieties witli large tubers and few or no seeds. The tomato {Ly coper si cum esculeii{u)n) (Fig, 143) is a native of Central and South America and is said to have been cultivated by the ancient inhabitants of Mexico. Its uses are well known. The pepper {Capi-icuin annuum) (Fig. 144) (rod pepper. Fig. 143. — Tomatoes. C. fastigiatum and C. fructescens, Cayenne pepper, and C. grossum, bell pepper) is also indigenous to tro})ical and sub- tropical America. The uses are well known. Tobacco (Nicodcoiu tahacum) is another well-known Amer- ican plant which is now cultivated in many parts of the world. This family also includes the deadly nightshade (Atropa helladonna) from which certain important drugs are obtained, the common black nightshade (Solanum nigrum), and many other interesting plants. GOOSEFOOT FAMILY 221 Propagation. — It is well known that the potato is grown from the tnbers, but the other cnltivated members of this'fam- ily are very generally gi'owu from seeds.' The seedlings are read- FiG. 144. — -The sweet pepper. ily transplanted. This family also contains a few tronblosome weeds which can iisnally be controlled by smother cro})*. goosi<:foot faafily (cii exopodiace.k") The members of ,]iis family are very widely distribnted. They are mostly herbaceons with alternate leaves ; flowers small, greenish, in spikes or beads, usually regular ; no corolla ; calyx 222 IMPORTANT FAMILIES OF PLANTS three to five lobcd (rarely one or no sepals) ; stamens as many as lobes of calyx or fewer; pistil one with one chamber; frnit one-seeded in a loose bladdery capsule or utricle. Beets, Spinach and Swiss Chard. — This family includes the common beet (Beta vulgaris) (Fig. 145), which is indigen- ous to both Europe and Asia and was used for five hundred years or more before the Christian Era. Some varied- ties are extensively used as a table vegetable, others for stock feed and still others for the manufacture of sugar. The spinach is an Asiatic plant which has been culti- vated and used from un- know^l time. The Swiss chard, which is so extensively used as a salad, is a variety of the common l>eet. BUCKWHEAT FAMILY (POLYGONACE.I:) Buckwheat. — This fam- ily includes the buckwheat (F ago pyrum escidenfum ) Fig. 145.-The table beet. ^-p-^^ ^^^^^ ^^ ^^.^^.^ p^.^^^^ which is well known. It was at one time kno\ni as beech wheat, owing to the resemblance of the seed to that of the beech, but this was gradually modified to " buckwheat." Rhubarb. — This family also includes the well-known vege- table, rhubarb or pie-plant (Rheum rhajwnticum), which is of East European or West Asiatic origin. Buckwheat is grown from seed. Rhubarb may be grown MULBERRY 223 from the seed, but will not come true to type and requires three years to come to maturity. It is much better to secure new plants by dividing the crowns. This family includes many important weeds; among the most troublesome is the sorrel, which grows in great abundance in sour (acid) soil. It can Fig. 146. — Buckwheat. be eradicated by heavy applications of lime and the use of legume crops. The docks are also members of this family. NETTLE FAMILY (URTICACE^) This family contains herbs, shrubs and trees and includes some very important plants. Flowers monoecious, dioecious or rarely with perfect flowers ; calyx regular ; stamens as many as the tubes of the calyx or fewer and opposite them; pistil one with two cells. The mulberry (Morus rubra, American red mulberry, and .V. alba, Asiatic white mulberry) is well known. The flowers 224 IMPORTANT FAMILIES OF PLANTS are unisexual and the plants are usually monoecious. Both male and female flowers are borne on short spikes and have a four-parted perianth or calyx. The white mulberry was intro- duced into Europe about the middle of the fifteenth century, into Mexico by Cortez in 1522 and into Virginia by James I Fig. 147— Fig. in 1619. It is extensively grown in China for the feeding of the silk worm. The American mulberry produces a very good fruit and the wood is very durable and seiwiceable for many purposes. The elms (Ulmus Americana, American or white elm; U. fulva, slippery or red elm; U. racemosa, corky elm) are among our most valuable shade and ornamental trees. HICKORIES 225 The common hop (Hutnulus lupulus) is well known. It is used in makini; yeast, beer and medicine. Fig and Rubber. — The genus Ficus includes the common fig {Ficus carica) (Fig. 147), the India rubber tree {F. elas- tica) and the banyan tree {F. bengalensis). The hemp {Canimbis sativa) also belongs to this family. Propagation. — The mulberry is usually grown from root cuttings, or from layerings, or by budding. New varieties are obtained from seeds. The elms are usually grown from seeds which mature very early in the spring and are sown at once, but may also be grown by layering or by grafting. Hops may be grown from seeds, from divisions or from hard wood cut- tings. Hemp is grown from seed and is one of the very im- portant fibre plants. WALNUT FAMILY ( JUGLANDACE.e) This very important family contains two valuable groups of trees, the walnut and the hickory. The flowers are monoecious. The staminate flowers are usually borne in catkins and each consists of a six-lobed (occasionally two^ or three-lobed) peri- anth and from six to forty stamens. The pistillate flowers are terminal and may be solitary, few or clustered ; the calyx tube is four-toothed and styles two in number. The fmit is a dru- paceous nut. Walnuts, — The American black walnut (Juglans nigra) is well known both for the nuts and for the high quality of the wood. The American butter-nut (/. cinerea) produces an ex- cellent nut, but the wood is not so valuable as that of the black walnut. The so-called English walnut (er cf separate flowers crowded on the torus. Com-pound' leaf. Orte composed of separate leaflets, or little leaves. Cone. A strobile, a multiple fruit having the shape of a cone. Cork'y. Of the texture of cork. Corm. A sort of bulb or fleshy stem. Co-rol'la. Inner perianth made up of petals. Co-ro'na. A crown. Cor'ti-cal bark. Outer bark. Cor'ymb. A flat-topped or convex cluster of flowers, each on its own foot- stalk, and arising from difl"erent points of a common axis. Cofy-le'dons. Lobes or seed leaves, or first leaves of the embryo. Creep'er. A plant that trails on the ground. Cre'nate. Bordered with round teeth. Cross'-pol'li-na'tion. The pollination of a plant by pollen from a difl'erent individual. Cru'ci-form. In the form of a Roman cross. Cryp'to-ga'mia. Name of the division of plants witljout flowers. Culm. Tiie straw of grasses. Cu'ne-ate, or cu-ne'i-form. Wedge-shaped. Cu'pule. A little cuj), as the cup of the acorn. Cus'pi-date. Having a sharp, stiflf point. Cu'ti-cle. Outer lamina of wall of epidermis. Cyme. Flower cluster Avith the oldest flowers at the to]> or centre. 250 GLOSSARY De-cid'u-ous, Fallin leaf to the apex, parallel to the midvein. Pa-raph'y-sis. A minute-jointed filament among the arcliegonia and antheridia of mosses. Par'a-site. A jilant obtaining noiirishiuent inimediately fi-om aiiotlier ])lant to which it attaches itself. Pa-ren'chy-ma. Soft cellular plant tissue, like the pulp of leaves, having no wood fibre. Pa-ri'e-tal. Attached to tlie nuiin wall of the ovarv. 254 GLOSSARY Per-en'ni-al. Living sevpral years. Per'fect flow'er. A flower having lx)tli stamens and pistils. Per'i-anth. Calyx or corolla, or both; the leafy parts of a flower surround- ing the stamens and pistils. Per'i-carp. The ripened ovary ; the covering of the seed. Pet'al. Part of the corolla. Pet'i-ole. The stalk of a leaf connecting the leaf with the stem. Phae'no-ga'mia, or pha-ne-ro-ga'mi-a. Name of that division of the vegetable kingdom which bears visible flowers. Pis'til. Organ of a flower, made up of ovary, style and stigma, or ovary and stigma. Pith. The soft tissue in the centre of the stems of dicotyledonous plants. Pla-cen'ta. The part of a pistil or fruit to which the ovules, or seeds, are attached. Plu'mule. The first bud of the embryo plant. Pod. A capsule, especially a legume. Pol'len. The fructifying cells Ixjrne in the anthers. Pol'len tube. The slender tube sent down from the pollen through the style of the pistil to the ovum in the ovule. Pol'li-na'tion. The act of transferring pollen to the stigma. Pol'y-cofy-le'don-ous. Having many (more than two) cotyledons, as in tlie i)ines. Pol'y-pet'a-lous. Having the petals separate from each other. Pol'y-sep'a-lous. Having the sepals separate from each other. Pome. A fruit like an apple. Pro-cum'bent. Trailing, prostrate. Pro-thal'li-um, pro-thal'lus. The minute primary growth from the spore of ferns which bears the true sexual organs. Pro'to-plasm. The primary organic substance of the cell. Pseu'do. False. Pter'i-do-phytes'. Ferns and fern-like plants. Pu-bes'cent. Covered with fine short hairs. Ra-ceme'. A flower cluster with an elongated axis and many one-flowered lateral pedicels. Ra'chis, or rha'chis. The principal axis in a spike, raceme, panicle or corymb. Rad'i-cle. Tlie rudimentary stem of a plant which supports the cotyledons in the seed, and from which the root is developed downward; a rootlet. Ra'phe. The continuation of the seed stalk along the side of an anatropous ovule or seed, forming a ridge or seam. GLOSSARY 255 Re-cep'ta-cle. Tlie apex of the flower stalk, fiom which the organs of the flower grow. Reg'u-lar. Having all the parts of the same kind alike in size and shape. Res'pi-ra'tion. Breathing; the absorption by plants of oxygen; the oxida- tion of assimilated products, and the release of carbon dioxide and watery vapor. Rha'chis. The axis of a spike inflorescence. Rha'phe. The continuation of the seed stalk along the side of an anatropous ovule or seed, forming a ridge or seam. Rhi^zome. An underground stem. Root. The descending axis of a plant; the part of a plant that grows down- ward into the ground. It bears no true buds. Root' cap. A mass of dead cells which cover and protect the growing cells at the end of a root. Root' stock. Same as rhizome. Sag'it-tate. Arrow shaped. Sam'a-ra. Indehiscent, winged fruit. Sap. The watery fluid taken up by the root, and moved through the vessel up to the leaves. Sap' wood. The last growth of wood in an exogen. Seed. Matured ovule. Se'pal, One of the parts of the calyx. Ses'sile. Without stean. Sol'i-ta-ry. Growing alone or singly. So'rus. A fruit dot of ferns. Spa'dix. A spike with a fleshy axis. Spathe. A large bract, or a pair of bracts, inclosing a flower cluster. Spike. An inflorescence in which the flowers' are sessile on a lengthened axis. Spo-ran'gi-um. A spore case in cryptogamous plants. Spore. A reproductive grain in flowerless plants, analogous to a seed in flowering plants. Sta'mens. The organs that produce pollen, consisting of fllament and anther. Sto'lon. A branch at the base of a plant which roots easily. Sto'ma. One of the openings in the epidermis of a leaf; a breathing pore. Style. That part of the pistil between the ovary and the stigma. Su-pe'ri-or. Above the ovary. Su-pe'ri-or o'va-ry. Ovary free from calyx. Sym-pet'al-ous. Having the petals united; gamoix'talous. 256 GLOSSARY Thal'lus. A mass of cellular tissue, usually in the form of a flat stratum or expansion, instead of stem and leaves. Tri'chome. A hair on the surface of a leaf or stem, or any modification of a hair. Tu'ber. A fleshy underground stem, or branch, with buds. Um'bel. An inflorescence in which the pedicels all spring from the same point, like the ribs of art umbrella. Veins. The system of branching vascular woody tissue seen in leaves. Xy'lem. That portion of a fibro-vascular bundle developed into wood cells. Zo'o-spore. A spore provided with one or more slender cilia, by the vibra- tion of which it swims in the water. INDEX Aceraceae, 198 Acids, 108 Agriculture, earliest records, 183 history of, 184 Alkaloids, 108 Algae, 169 Almond, 206 Althea, 193 Anatomy, 93 • Annuals, 23 Annular rings, 31, 99, 100 Anther, 61 Antheridiiun, 161, 165, 167, 171 Apetalous, 56 Apium, 215 Apple, 205, 240 Archegonium, 160, 101, 105, 167 Asparagus, 228 Avena, 230 Bacteria, 117, 169, 177 Banana, 227 Barley, 230 Bean, 6, 14, 202, 237 Beets, 222 Berries, 206-208, 217, 235, 240 Biennials, 23 Blade of leaf, 48 Brassiea, 185 Bread mold, 172 Breeding of plants, 147 Broom corn, 232 Bryales, 166 Bryophytes, 164 Buckwheat, 222 Budding, 39 Bud scales, 51 Buds, 31, 40, 41 Bundles, fibro-vascular, 97, 100 Cabbage, 185 Calyptra, 164 Calyx, 54 modifications of, 60 Cambium, 31, 97 Cannabis, 225 Carrot, 215 Capsicum, 220 Capsule, 164 Carbohydrates, 107 formation of, 115 Caruncle, 7, 12 Castanea, 227 Castor bean, 7, 14 Ca,tkin, 65 Celery, 215 Cells, 93, 98 Cellulose, 107 Chemical composition, 105 Chenopodiaeeae, 221 Cherry, 206, 240 Chestnut, 227 Chlorophyll, 46 Cinchona, 215 Circulation, 118 Citrus, 190 Classification, 65, 70 Clover, 200, 203, 238 Cocoa, 193 Coffee, 215 Compositae, 216, 235 Cones, 122 Convolvulaceae, 218 Com, 6, 15, 231, 236 Corolla, 54, 60 Corylus, 227 Corymb, 64 Cotton, 191, 241 Cotyledons, 4. 5, 10, 16 257 258 INDEX Cruciferea, 185 Cryjitogams,. 70 Cucurbitacete, 211, 235 Cupulifeiae, 22G Currants, 211, 235 Cycadales, 124 Cyme, G5 Daucus, 215 Deciduous, 122 Dicotyledons, 4, 70 Dioecious, 58 Dioscoraecese, 218 Diseases of plants, 139, 141, 177 Ecological relations, 126 Egg, 76 Eggplant, 239 Elaters, 168 Elm, 224 Embryo, 3, 5, 76, 83 Endogenous, 31, 71 Energy, 111 Epicotyl, 7 Epigynous, 63 Equisetum, 161 Exogenous, 31, 71 Exosmosis, 113 Evergreens, 121 Fagopyrum, 222 Fats, 107 Ferna, 158 Fertilization, 75, 76, 123 Fertilizers, 130 Fibrovascular bundles, 97 Ficus, 225 Filaments, 61 Flax, 193 Flowers, 54, 57, 58, 64, 65, 75 Foliage, first, 10 Foods, 5, 19, 22, 111 Forestry, 134 Fruits, 83 Fungi, 169 • Gamopetalous, 60 Galls, 142 Gas, formation of, 16, 115 Geography, 131 Geotropism, 18 Germination, 12, 15 Goosefoot, 221 Gossypium, 191 Gourd, 213 Grafting, 39 Graminete, 228 Grape, 197 Grass, 228, 239 Growth, 41, 42 Gumbo, 191 GjTiinosperms, 70, 121 Halophyte, 128 H'austoria, 24 Hazelnut, 227 Head, 65 Heart wood, 100 Heat, 15 Heath, 217 Hemp, 225 Hepaticea;, 164, 166 Hibiscus, 191 Hickories, 225, 235 Hilum, 7, 12 Hollyhock, 193 Hop, 225 Horsetail, 161 Hordeum, 230 Humulus, 225 Humus, 117 Hybridization, 148 Hydrocarbons, 107 Hydrophyte, 127 INDEX 259 Hypocotyl, 7 Hypogynous, 63 Indusiuni, 159 Inflorescence, 64 Iponioese, 218 Juglandaceae, 225 Lamella of leaf, 48 Leaves, 4, 45, 48-51, 93, 102, 131, 142, 159 Leguminoseae, 199 Light, 15, 45 LiliaceiB, 228, 232 Linaceffi, 193 Linum, 193 Liverwort, 164, 166 Lycopersicuni, 220 Madder, 215 Mallow, 191 Malvaceae, 191 Maple, 198, 234 Marchantia, 166 Medullary rays, 99 Melons, 213 Mesopliyte, 128 Micropyle, 7 Microsporangia, 123 Midrib, 48 Millet, 230 Minerals, 116 Moisture, 9, 12. 15, 19 Mould, 172 Monocotyledonous, 4, 70 Morning glory, 240 Morus, 223 Mosses, 164 Mulberry, 223 Musca, 227 Musci, 164 Mustards, 185, 186, 234 Mutation, 147 Myoetozoa, 178 Myxoniycetes, 178 Nettle, 223 Nicotiana, 220 Nightshade, 219 Nitrogen, 116, 117, 129 Oak, 226, 235 Oats, 230, 237 (Edogonium, 171 Oils, 107, 108 Okra, 191 Onion, 228 Operculum, 164 Orange, 196 Organic acids. 108 Oryza, 230 Osmosis. 29, 112 Ovary. 62, 63 Ovum, 76 Ovules, 62, 83 Ox.ygen, 9 Parenchyma, 99 Parsley, 215 Parsnip, 215 Pastinaca, 215 Pea, 199, 203. 237 Peach, 205, 240 Peanut, 203 . Pear, 205, 240 Pepper, 220. 239 Perennials. 23 Perianth, 55 Perigynous, 63 Peristome, 164 Petal, 54 Petiole. 48 Pliloom, 08 260 INDEX Photosynthesis, 46 Pistil, 54, 02 Placenta, 63 Plant breeding, 147 diseases, 139 foods, 111 geography, 131 hair, 103 societies, 147 Plants, composition of, 105 uses of, 183 Plum, 240 Plumule, 14 Pollen, 02, 123 Pollination, 75, 79, 80, 122 Polygonaceous, 222 Polypetalous, GO Populous, 227 Potato, 219 sweet, 218, 240 Proteins, 108, 110 Prothallus, 160, 164 Protonema, 164 Protoplasm, 93 Pteridophytes, 158 Pyrus, 205 Quercus, 226 Quince, 240 Quinine, 215 Raceme, 64 Radicle, 7, 12 Radish, 189, 234 Raphe, 7 Rays, medullary, 99 Reproduction, 74 of ferns, 100 Respiration, 51 Rheum, 222 Rhizome, 37 Rhizopus nijrricans, 172 Rhubarb, 222 Ribs of leaves, 48 Rice, 230 Rings, annular, 32, 99. 100 Roots, 4, 18, 20, 23-25, 27-30, 101 Root hair, 25, 26 Rosacete, 204 Rose, 204 Rootstock, 37 Rubiacese, 215 Rue, 195 Rutacete, 195 Saccharum, 232 Saccharomyces, 172 Salicacese, 227 Salix, 227 Saprolegnia, 173 Sapwood, 100 Saxifragaceae, 211 Saxifrage, 211 Scales of buds, 51 Scutellum, 11 Secale, 230 Seeds, 3, 4, 7, 75, 77, 78, 83, 88^ 89, 137, 239 Seedling, 3 Sepal, 54 Setaria, 230 Seieties of plants, 127 Soil, 128, 129 Solanceae, 219 Solanum, 219 Sorghum, 232 Sori, 159 Spadix, 65 Sperms, 171 Sphagnales, 166 Spike, 65 Spinach, 222 Spirogyra, 94, 170 INDEX 261 Sporangium, IGO, 173 Si>orop.hyll, 1G2 Sprouting, 7, 10 Stamen, 54, 01, 123 Starch, lOG Stems, 4, 31-33, 35, 38, 47, 93, 98, 121 Sterculia, 193 Sterculiaceae, 193 Stigma, 62 Stomata, 38 Style, 62 Sugar, 107, 116, 232 Sunflower, 216 Sunlight, 40 Sweet potato, 218, 240 Tannins, 108 Temperature, 130 Thallophytes, 169 Theobroma, 193 Tobacco, 220 Tomato, 220, 239 Torus, 54 Transpiration, 113, 114 Trees, 135-137 Trichomes, 25, 103 Triticiun, 229 Tropophyte, 128 Turnips, 188 Ulmus, 224 Ulothrix, 171 Umbel, 05 Umbillifera', 215 Urticaceae, 223 Uses of plants, 183 Vacciniaceae, 217 Variations, 147 Vaucheria, 171 Veins, 48 Vine, 196 Violaceae, 189 Violet, 189 Vitaceae, 196 Vitis, 197 Walnut, 225, 235 Warmth, 8 Water, 15, 16, 105, 112, 114, 120 Weeds, 150, 239 Wheat, 229, 237 Willow, 227, 230 Wood, 100 Xerophytes, 128 Xylem, 98 Yam, 218 Yeast, 172 Zea, 231 Zingibracea;, 227 Zoospores, 171 Zygospores, 171 nOeERTY UBRAHY V. C. State Colkge