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The Cambridge Manuals of Science and 
 Literature 
 
 PLANT-LIFE ON LAND 
 
 CONSIDERED IN SOME OF ITS BIOLOGICAL ASPECTS 
 
CAMBRIDGE UNIVERSITY PRESS 
 
 aOttHOtt: FETTER LANE, E.G. 
 
 C. F. CLAY, Manager 
 
 (SXsinbmQ\j: loo, PRINCES STREET 
 
 ILontion: H. K. LEWIS, 136, GOWER STREET, W.C. 
 
 iSexlin: A. ASHER AND CO. 
 
 ILfipjtg: F. A. BROCKHAUS 
 
 {^efaj lorfe: G. P. PUTNAM'S SONS 
 
 ISombau anU (Calcutta: MACMILLAN AND CO., Ltd. 
 
 A/^ rights reserved 
 
(JTambrtlige : 
 
 PRINTED BY JOHN CLAY, M.A. 
 AT THE UNIVERSITY PRESS. 
 
 With the exception of the coat of arms at 
 the foot^ the design on the title page is a 
 reproduction of one used by the earliest kno-ivn 
 Cambridge printer, John Siberch, 1 5 2 1 
 
CONTENTS 
 
 CHAP. PAGE 
 
 I. Present-day Botany — a Contrast .... 1 
 
 II. The Beach and Rocks 12 
 
 III. The Bracken Fern . ... . . .29 
 
 IV. The Flower and Metamorphosis .... 49 
 
 V. Pollination and Fertilisation 68 
 
 VI. Fixity of Position as a Factor in the Evolution of 
 
 Plants 81 
 
 VII. Plant Population 102 
 
 VIII. Sand Dunes 122 
 
 IX. Golf Links 145 
 
 X. General Outlook on the Flora of the Land . .154 
 Index and Glossary 164 
 
 ^^ *A«I.C0UE6EUBfiABy. 
 
CHAPTER I 
 
 PRESENT-DAY BOTANY— A CONTRAST 
 
 Few pursuits are more thoroughly misunderstood 
 by the average person of education than that of the 
 present-day botanist. It is not want of sympathy 
 which leads to this. Almost everyone has an interest 
 in the plants which he sees around him, sometimes 
 from the point of view of their beauty, sometimes of 
 their use to himself or to the human race at large : 
 sometimes the interest is the more philosophical one 
 of their place in organic nature, or of their origin 
 in point of time as disclosed by the evidence of the 
 fossils. On one or another of these grounds the 
 botanist finds some feeling for the science of his 
 choice already alive in the minds of his friends. 
 
 The conversation in ordinary educated society 
 may often throw an illuminating light, revealing the 
 layman's estimate of what a botanist is actually 
 about. In this case it commonly appears that the 
 estimate errs by being belated. Old time-worn 
 aspects of the science are assumed to be still the 
 
 B. 1 
 
 PBOPERTY LlBUlll 
 N. C. State College 
 
2 PLANT-LIFE ON LAND [ch. 
 
 living problems of the day. In no point does this 
 emerge more clearly than in the undue importance 
 attributed to the finding and recording of new 
 species and varieties. This is a survival of the time 
 when the science, still in its infancy, was mainly 
 engaged in the recognition and tabulation of living 
 forms. Personal credit was then apt to be measured 
 by the number of the new determinations. Far be 
 it from me to suggest that the process of recording 
 new species is yet complete, or even approaching 
 completion. But whereas in earlier periods most 
 botanists were engaged in this duty, the work is 
 now so far advanced that it remains in the hands of 
 comparatively few. It is indeed a fact that some of 
 the most prominent investigators and writers have 
 never recognised or described a single new species. 
 An illustration of the misconception on this point 
 in the minds of well-educated people may be quoted 
 in my own case. When preparing for a recent visit 
 to collect Ferns in Jamaica, a kindly Dignitary of the 
 Church expressed the hope that I should return with 
 several new species. I, however, congratulate myself 
 on looking over my collections that all my specimens 
 fall under well-known and recorded determinations. 
 The reason for this callousness to novelties may be 
 demanded : it is this. In the island of Jamaica the 
 Fern-Flora has been so well worked, that all the 
 most prominent and typical plants have been already 
 
I] PRESENT-DAY BOTANY 3 
 
 discovered and described. If new species were found, 
 the chances are strongly against their presenting any 
 feature of special importance for purposes of com- 
 parison with others : and in the absence of such the 
 duty of describing and delineating is unprofitable 
 for one whose aim is comparison with a view to 
 tracing Descent. If this be the case for Jamaica, 
 what will be the chance of discovery of important 
 novelties in our own carefully searched islands? 
 The home botanist can only look for fresh "finds" 
 among minute and obscure forms, or among the 
 subordinate shades of varietal distinction. To most 
 of us the game is not worth the candle at home, and 
 we do not lay ourselves out for it in the better known 
 localities abroad. Specially organised expeditions in 
 little known countries where much that is found is 
 new, are a difterent matter; but they should be 
 undertaken only by those specially trained for the 
 purpose. Thus the recording of new forms no longer 
 takes the premier place in the progress of the science. 
 If the conversation at some social gathering turns, 
 as it often may when a botanist is present, to the floral 
 decorations, the unfortunate victim of a misplaced 
 confidence will as likely as not betray a lamentable 
 ignorance of the most fashionable new varieties of 
 decorative plants circulated from some celebrated 
 nursery, or be unable to give the usual social or 
 trade name of some common greenhouse plant; 
 
 1—2 
 
4 PLANT-LIFE ON LAND [ch. 
 
 though he might give an hour's lecture on its 
 structure, and its systematic and biological charac- 
 teristics. The sympathetic layman is disappointed 
 and perplexed when he finds this, for he dearly loves 
 a name. He does not realise that in point of fact 
 names are necessary symbols : a means of recording, 
 and nothing more: and that for the student the 
 interest in a given plant may have begun long before 
 the identification, and will as a rule intensify with 
 study quite apart from the exact designation. It 
 is when he puts his observations on public record 
 that the necessity arises for accurate determination. 
 The names which are used to stamp specific or 
 varietal identities of plants are like the words of 
 a language. Their value per se is small. It is in 
 collocation that identities stamped by specific names 
 acquire their interest and their worth. The individual 
 who stores his mind merely with the names of plants 
 may know as little of the science as one who 
 memorises a dictionary would know of literature. It 
 is considerations such as these that justify many 
 botanists in their neglect to commit a multitude of 
 names to memory. The knowledge of characteristics 
 and of relations is the important matter, and this 
 should go along with a facility in ascertaining the 
 correct naming whenever it is required for purposes 
 of description, in case the memory has failed to bear 
 that burden. 
 
I] PRESENT-DAY BOTANY 5 
 
 Which of us has not been assumed to know at 
 once by sight and to be able to name the various 
 Conifers growing in the plantations round some 
 country house, or planted proudly as "solo trees" 
 in prominent spots to challenge the eye? The 
 assumption is complimentary, but it is apt to be 
 embarrassing. The plain fact is that the Coniferae 
 are a family with an irritating sameness of habit 
 for those who have not made them a special study, 
 however distinct their features may appear to those 
 who live with, and know so to speak personally, 
 certain individual specimens. When one is found 
 at fault in the specific distinctions of Abies or 
 Cupressus, there is some risk of attainments in other 
 branches being unduly discounted. Sucli, knowledge 
 is doubtless desirable, as is all knowledge : but to the 
 majority it would be but so much mental ballast, and 
 would take no direct part in the working of the 
 intellectual ship. 
 
 Another subject which leads to misunderstanding 
 is Horticulture. Theoretically every botanist ought 
 to be an expert gardener, and doubtless every one of 
 them would wish to be. It will usually be assumed 
 that he is, but in many cases that assumption is ill 
 founded. The man whose life-work is in the herbarium 
 may have little time or opportunity, or it may be even 
 inclination for horticulture. The laboratory student, 
 even with a good knowledge of the current problems, 
 
6. PLANT-LIFE ON LAND [ch. 
 
 is often in the same position. He will probably use 
 a microtome better than a trowel, and judge better 
 of the methods of fixing and embedding with a view 
 to cutting sections than of potting. Such men will 
 probably have spent, perforce, the greater part of their 
 time in towns, and will thus have missed the experience 
 which falls naturally to those who live in the country, 
 and are observant. 
 
 Still another ground for misunderstanding is the 
 terminology of the science. No subject has been 
 more heavily weighted by technical terms and uncouth 
 names than Botany. The very pronunciation of them 
 is often an offfence to the ear of the cultivated classic, 
 while to those who love nature and natural things 
 the language commonly used in Botany is an effectual 
 barrier to the pursuit of this spontaneous line of 
 interest. A certain thoughtlessness of those within 
 the pale in the use of what can hardly be designated 
 otherwise than as their "slang" must be admitted. 
 It has given reasonable ground for the idea that a 
 botanist loves his terminology, and even glories in it. 
 As a matter of fact the profession groans under the 
 burden. It is largely a legacy of a misguided past, 
 which can only be thrown oif by a determined and 
 collective effort. It is true old terms are constantly 
 becoming obsolete, and dropping out of use, but 
 others are being introduced to meet current needs. 
 The result is that the vocabulary to be heard at 
 
I] PRESENT-DAY BOTANY 7 
 
 any sitting of the Botanical Section of the British 
 Association is certainly not such as is "commonly 
 understanded of the people." The practical effect 
 of this is an unhappy isolation, and the unconscious 
 ostracising of many whose interests are already 
 engaged in kindred questions. Occasionally among 
 the exponents of the subject a brilliant exception 
 arises, who either from the nature of his investigation, 
 or fi-om his power of conveying it, or better from the 
 combination of both, succeeds in touching the general 
 interest : and perhaps the most striking example was 
 Charles Darwin, whose use of technical expressions 
 in the Origin of Species was reduced to its lowest 
 terms, a fact which conduced in no small degree to 
 its effect upon the general reading public. 
 
 Several distinct causes of the misunderstanding 
 between the modern botanist and the lay public 
 have now been recognised. They all arise more or 
 less directly from a common source. It is not generally 
 realised how far the science has progressed in its 
 differentiation. In the course of the last half century 
 there has been a vast increase in the number of those 
 who pursue it. Institutes in Universities and else- 
 where have multiplied greatly, each with its more or 
 less complete staff of workers. Most of these are 
 contributing to knowledge by practical enquiry of 
 some sort, and their observations and arguments are 
 published in a continuously growing stream. Professor 
 
8 PLANT-LIFE ON LAND [ch. 
 
 Scott-Elliott in his Botany of To-day has estimated 
 that about a quarter of a million pages of printed 
 matter relating to botany are produced annually. 
 Naturally it has become increasingly difficult for any 
 one mind to grasp the multitudinous details, or to 
 follow the descriptions of them as they appear. 
 Accordingly it has become necessary for each one to 
 specialise, if he is to be a practical worker at all : to 
 take up some limited area of the science, and make 
 it his own by reading and by personal observation. 
 In proportion as this is realised other parts of the 
 subject are apt to be neglected. This is the point 
 which has not been fully grasped. It still remains 
 to be learned that an expert on fossils of the coal 
 may not ever have grown a living plant ; an authority 
 on physiology may be sadly lost in the determination 
 of rare exotics ; a leading cytologist may be hope- 
 lessly puzzled by the identification of the Conifers ; 
 or a student of Algae may know little or nothing of 
 the source and supply of condiments and drugs. 
 And yet all of them pass under the comprehensive 
 name of "botanist." 
 
 On these facts it may perhaps be hastily con- 
 cluded that the position of the science is highly 
 unsatisfactory : that each will take his own way, and 
 that coherence of intention among the workers is at an 
 end. It must be admitted that there is some danger 
 of this. It is difficult even for the most enthusiastic 
 
I] PRESENT-DAY BOTANY 9 
 
 student to keep himself adequately informed on the 
 general progress of the science as a whole. And 
 were it not for the compulsion which binds the 
 professional botanist in most cases to his duty as a 
 teacher, the risk would be greater than it actually is. 
 Fortunately almost all have to take their turn both 
 in elementary and advanced teaching of branches of 
 the science quite apart from that which is the chosen 
 speciality. This compulsion tends to right the balance, 
 and leads to a periodical revision of the science, as 
 it grows, by each teacher. Thus his interest is 
 compulsorily kept alive over the general field of the 
 subject. 
 
 In presence of this pronounced tendency to 
 specialism, the amateur is apt to miss the main 
 ends which the expert has ultimately in view. It 
 would seem accordingly to be worth while to embody 
 in a series of short essays some reflection of the 
 outlook of an average botanist, himself a specialist, 
 it may be, upon the ordinary objects that surround 
 him. To show how he regards such vegetation as he 
 would encounter on a holiday, and to touch lightly 
 and with the least possible technicality upon some 
 of the problems which arise in relation to them. 
 Such lines of thought converge more or less directly 
 towards one central problem, still so far from ulti- 
 mate solution, viz., how the plant-organisms we see 
 around us came to be such as they are, and where 
 
10 PLANT-LIFE ON LAND [ch. 
 
 they are ? The eifort is in fact to reconstruct evolu- 
 tionary history. It is clear when once this general 
 problem is enunciated, its solution must involve 
 enquiry not only as regards form and structure, but 
 also as regards function with which form and structure 
 are so closely related. These questions expand 
 naturally into numerous cognate phases of enquiry, 
 such in fact as the various individual specialists have 
 made the subject of their detailed research. Thus, 
 while apparently driving lonely furrows, they are all 
 at work for a common end. But the field is so vast 
 that the casual onlooker may fail to grasp the general 
 scheme, by reason of visualising only that part of it 
 which happens to be nearest to him. He may see 
 perhaps a solitary investigator working in a way that 
 may seem trivial or unsatisfactory. But the doubts 
 of the critic may really arise from the fact that the 
 value of the work cannot be estimated without some 
 knowledge of its relations to the ultimate goal. On 
 the other hand, it must be confessed that it is not 
 every worker who understands the general scheme of 
 which his labour forms a part, however well he may 
 be carrying out his own particular research. And 
 furthermore, since there is seldom any master-hand 
 directing the efforts of individuals, some workers, 
 having a perverted idea of the general scheme, may 
 lay out their own investigations on mistaken lines, 
 and their labour may be in vain. This is the fate 
 
I] PRESENT-DAY BOTANY 11 
 
 which too often awaits the zealous but isolated 
 amateur. 
 
 The fact is, regret it as we may, that the day of 
 specialisation is upon us. The good old times, in 
 many ways so sound and so stimulating, when one 
 mind could compass a circle of the sciences and even 
 contribute to them all, are gone for ever. Now it is 
 more than the man of ordinary ability can do to keep 
 himself even moderately informed over the whole area 
 of a single science. Hardly any aspire to a special 
 knowledge of more than one branch of the many into 
 which each science is divided. It is useless to resist 
 this state of affairs so naturally forced upon us. The 
 important point is, however, to be fully aware of the 
 weaknesses which are liable to follow in the wake 
 of specialisation, and to use every opportunity to 
 neutralise their results. The most effective safeguard 
 is the proper grounding of every young student in a 
 cognate group of the sciences before he is encouraged 
 or even allowed to specialise. And those sciences 
 should be so taught that he shall grasp thoroughly 
 the lines of reasoning upon which their structure 
 depends. So prepared, the young investigator may 
 specialise with safety, the broad base of education 
 being ready to support the superstructure of his 
 exact, but localised, knowledge. 
 
CHAPTER II 
 
 THE BEACH AND ROCKS 
 
 BoTANiCALLY speaking the sandy Beach between 
 the tide-marks is an uninteresting thing, for it is 
 desert. You may walk for miles along it, and find 
 below the high-tide mark no sign of active vegetation. 
 Seaweeds may be littered here and there, but they 
 will be in varying stages of decay. You take up 
 a handful of sand and examine it : it will be chiefly 
 composed of grains of silica, but with many fragments 
 of shells of animals, and occasionally of the lime- 
 incrusted remains of certain coralline seaweeds. But 
 the conspicuous fact is that active vegetable life is 
 absent from the moving sand. The reason for this 
 is not far to seek. It is that, apart from the floating 
 life of the open waters, or Plankton, as it is called, 
 seaweeds with few exceptions require a fixed sub- 
 stratum. How diflerent from the barrenness of 
 the loose, disintegrated, and ever shifting sand is 
 the condition of any rock or wooden pile Avhich 
 you may see exposed between the tidal limits, or 
 
CH. II] THE BEACH AND ROCKS 13 
 
 extending below the low-tide mark far into the 
 deeper water. Such fixed surfaces, except where 
 they may be exposed to the grinding action of the 
 sand washed past by the movement of the waves, 
 are found covered by seaweeds of various forms 
 and colours. These constitute a vegetation of 
 Algae, widely different from that of the land. Their 
 characters of outline, of function, and of propagation 
 are peculiarly their own. 
 
 The spread of this characteristic Flora of the sea 
 is limited upwards by the high-tide mark, and 
 though some Algae appear content with a short 
 immersion at high w^ater, they are all dependent 
 upon access to sea-water at intervals, while some 
 require to be constantly submerged. Some straggle 
 up estuaries and river-mouths till the brackish water 
 is reached, but do not thrive in fresh water. On the 
 other hand certain genera, such as Batracliosjjcrmum 
 and Lemanea, allied to the Red Seaweeds by their 
 structural and propagative characters, are common 
 in freshwater streams but do not occur in the 
 sea. These plants are green in colour, and might 
 paradoxically be described as green freshwater 
 red seaweeds. Passing through the zone of sea- 
 weeds do>Miwards to the low-tide mark and beyond 
 it, it becomes a point of interest to enquire what 
 are the limits of depth to which this Algal Flora 
 may extend. It appears that at about 150 feet 
 
14 PLANT-LIFE ON LAND [ch. 
 
 below the sea-level as a rule all growth ceases, 
 though in some very transparent waters the limit 
 may be deeper. It is in fact the fading out of the 
 light necessary for the self-nutrition of these plants, 
 by its absorption in passage through the great depth 
 of water, that imposes a limit of extension upon the 
 seaweeds downwards. And so we may understand 
 that, exclusive of the floating Plankton, the character- 
 istic Flora of the sea is restricted to a comparatively 
 narrow zone lying between high -tide mark and some 
 150 feet below low water. 
 
 The plants which constitute this Algal Flora, so 
 restricted in its spread, fall into three large groups, 
 which are roughly characterised by their colour as 
 the Green, Brown, and Red Seaweeds. Not that the 
 mere tint is absolutely distinctive, as the already 
 quoted case of Lemanea shows ; but it happens that 
 the colours mentioned run in a measure parallel with 
 other characteristics of form and propagative method 
 by which the large groups are more strictly defined. 
 It has been found that the colouring has its physio- 
 logical meaning and importance in relation to the light 
 so necessary for the self-nutrition of these plants. 
 In the Brown and Red Seaweeds the greatest activity 
 is carried on in the light of that part of the spec- 
 trum which is complementary to their own colour. 
 Ordinary green plants make special use of the rays 
 in the red end of the spectrum, but for Brown and 
 
II] THE BEACH AND ROCKS 15 
 
 Red Seaweeds rdys further along the spectrum are 
 specially effective, and it is such rays, in the direction 
 of the blue end of the spectrum, which penetrate 
 furthest into the depths of the sea-water. Thus 
 the colourings have a probable relation to the 
 nutrition of the Seaweeds which show them : and 
 in particular, the possession of a brown or red tint 
 makes self-nutrition at great depths possible, while 
 it does not appear injuriously to aifect life under 
 less rigorous conditions. 
 
 From the circumstance that the Red and Brown 
 Seaweeds are by their colouring specially able to 
 use in their nutrition such light as penetrates far 
 into the depths of sea-water, it might be expected 
 that they Avould find their place exclusively at these 
 low levels. But it is not so. There is no exact scale 
 of zonation of the three types of seaweeds according 
 to depth of water. Representatives of all may be 
 found near to the high- tide mark. It is, on the other 
 hand, an interesting fact that such full-green Algae 
 as Struvea, which show no colour specialisation 
 different from land-plants, may live at so great a 
 depth as 150 feet. But speaking generally the Red 
 Seaweeds are certainly more prevalent at the lower 
 levels, where the green are present in less numbers. 
 The Brown extend from the highest levels downwards, 
 but stop short of the greater depths. As regards 
 genera and species, however, there is more definite 
 
16 PLANT-LIFE ON LAND [CH. 
 
 zonation, and it is a familiar matter of observation 
 how the dense tassels of the yellowish Pelvetia 
 almost take possession of the highest levels on our 
 shores, followed downwards by definite zones of 
 tangles, such as Fnciis platy carpus and Ascopliiilliim 
 nodosum, while the strange Hhnanthalia, with its 
 thong-like fruiting branches rising from the cup- 
 shaped base, are only met with below half-tide 
 mark. Similar sequences of zonation may be noted 
 in the Red Seaweeds also. 
 
 One point of distribution is specially worthy of 
 remark : it is tliat certain of the Green Algae are 
 stimulated to active growth by sewage impurities, 
 which seem to affect the others adversely. In the 
 neighbourhood of a harbour, and conspicuously 
 near to the drainage-outfalls, the Green Seaweeds 
 are in the ascendant : so much so that their presence, 
 in quantity, may often serve as an indication and a 
 warning. In recent years the growth of vast masses 
 of the bright green Sea-Lettuce ( TJlva latissima), and 
 its subsequent decay as the season progresses, has 
 been a cause of serious nuisance along the shores 
 which border on the relatively impure waters of 
 Belfast Lough and Dublin Bay. No method has 
 yet been devised for checking its growth. 
 
 The Sea-Lettuce is common all round the British 
 coasts, being found attached to rocks, piles and 
 piers. It consists of a thin filmy expansion of 
 
n] 
 
 THE BEACH AND ROCKS 
 
 17 
 
 simple outline and full green colour, and it is fixed 
 by a narrow stalk which widens into a minute 
 attachment disc. The whole plant is very soft and 
 
 iC^^ 
 
 Fig. 1. Ulva lactuca. 1. A complete specimen of the plant. 
 3. A longitudinal section from the upper part of the flat ex- 
 pansion, showing the two layers of cells of which it is composed. 
 2. A similar section from the lower part, showing similarly the 
 two layers of cells ; several of the latter have elongated into 
 tubes or hyphae (h). 2 and 3 are highly magnified. (From 
 Oltmanns' Morplwlogie und Biologic tier Algeii, after Thuret.) 
 B. 2 
 
18 PLANT-LIFE ON LAND [ch. 
 
 flexible, so that when left by the receding tide it 
 adheres to the substratum, but floats off" again as 
 the Avater rises, yielding to every motion, but re- 
 maining fixed at the base during life (Fig. 1, i). 
 Sections show that the flat expansion is composed 
 of two layers of oval cells, which are all alike, 
 having a protoplast containing a nucleus and green 
 chlorophyll-body, and surrounded by a swollen cell- 
 wall. But towards the base of the plant some of 
 the cells may be elongated downwards into tubes, 
 which force their way between the two layers, and 
 reaching the base add to the strength of the 
 attachment-disc (Fig. 1, 2, 3). Thus constructed the 
 plant may grow to a large size, though still pre- 
 serving its simple outline. 
 
 There are other genera of Green Algae, diftei-ing in 
 their form, but resembling Ulva in all essential points, 
 such as the common genus Enteromorpha with its 
 tubular body, gut-shaped as its name implies, produced 
 by the separation of its two layers which correspond 
 to those of Ulva ; or Monostroma, in which at an 
 early stage the tube is ruptured, so that a broad 
 green expansion is produced, only one layer of cells 
 in thickness. But all such forms, including Ulva 
 itself, are held to be merely consequences of the 
 elaboration of the simple filament of cells, such as 
 is seen in the genus Ulothrix, various species of 
 which inhabit fresh or salt water (Fig. 2, A). If the 
 
II] THE BEACH AND ROCKS 19 
 
 cells of a filament like that of Ulothrix be divided 
 longitudinally as well as transversely, the transition 
 to such forms as those just described would be easy: 
 and judging from the fact that all these Algal types 
 begin life as simple filaments, this conclusion seems 
 to be a highly probable one. AVhen it is noted 
 further that the minute cells composing these Algae 
 are essentially like those of Ulothrix, the mode of 
 their origin can hardly be held to be any longer in 
 doubt. 
 
 In plants at large a quiescent period of self- 
 nutrition precedes propagation, and these Algae are 
 no exception. It matters not whether it be a simple 
 filamentous plant like Ulothrix, or a large expansion 
 such as Ulva, during this first period it is capable of 
 growth accompanied by cell-division to which there 
 is no ostensible limit. The relatively large body thus 
 produced, consisting of thousands of cells in such 
 a plant as Ulva, is apparently inert, for the living- 
 protoplasts are enclosed and fettered each by its 
 restricting cell-wall (Fig. 1, p. 17). The vegetative 
 period is thus one of bodily quiescence, however great 
 the physiological activity may be. But when in any 
 matured and well-nourished plant the circumstances 
 are favourable for propagation, a change may occur 
 in individual cells, which leads to a period of very 
 active movement. Their protoplasts, after sub- 
 division, escape from the restricting cell-walls into 
 
 2—2 
 
20 PLANT-LIFE ON LAND [ch. 
 
 the surrounding water, each portion forming itself 
 into a separate and actively motile body, or zooid. 
 These minute naked bodies are slightly elongated 
 or pear-shaped, while long cilia are attached to the 
 narrower end of each, the active lashings of which 
 give it rapid movement from place to place (Fig. 2, C). 
 There are in Ulothrix three different types of the 
 zooids which thus escape into the water. Some are 
 relatively large, and may be produced singly without 
 division of the contents of the mother-cell, or more 
 commonly by division of them into two or more parts 
 according to the size of the mother-cell. They escape 
 through an opening of the cell-wall into the water 
 (Fig. 2, B). Each has four motile cilia attached 
 to its narrower end. A period of active movement 
 in water ensues, varying in length according to 
 circumstances. In this way these zoospores may 
 scatter in different directions, and travel a relatively 
 considerable distance. They finally settle upon some 
 solid substratum, forming each a new cell- wall and 
 grow out transversely to their former axis. A 
 rhizoid of attachment is put out in one direction, 
 and in the other there grows a new filament like 
 the original parent. There is thus a means both of 
 increase of numbers and of dispersion of the new 
 individuals. Other similar but rather smaller zooids 
 have been distinguished as micro-zoospores. They are 
 of the same type as the first, but are produced in 
 
II] 
 
 THE BEACH AND ROCKS 
 
 21 
 
 larger numbers in each parent-cell. In size they 
 resemble the third type, which are the sexual zooids, 
 
 Fig. 2. Ulothrix zonata, showing formation of zoospores. A- A 
 filament in the vegetative condition, B = a, filament whose cells 
 are producing zoospores. C = a single zoospore. JD = a zoospore 
 coming to rest: o = eye-spot: c = pulsating vacuole. ^ = germi- 
 natmg zoospores. F=micro-zoospore. G 1 — 3 = germinating 
 microspores. A,Bx200. C— G 1, 2 x 333. (? 3 x 166. (After 
 Klebs.) 
 
 or gametes ; but these are readily distinguished from 
 them by the number of their cilia, which are two in 
 
22 PLANT-LIFE OX LAND [CH. 
 
 place of four. They differ also in their behaviour, 
 for it has been observed that the gametes which 
 escape from different filaments when they meet 
 coalesce in pairs (Fig. 3 A — D). The result of the 
 fusion is a cell called a zygote (E). It soon loses its 
 cilia, takes a rounded outline, and forms a cell-wall (F). 
 After a period of rest the zygote germinates, bursting- 
 its cell- wall, and the contents divide into four parts 
 (F, G), each of Avhich may grow into a new filament 
 like the parent. The propagative methods in Uli'a 
 and other related Algae are similar to those in Ulo- 
 tlirix, but they have not been followed out with the 
 same exactitude. It has been shown by Professor 
 Klebs that the various forms of the motile propagative 
 cells do not follow in any necessary sequence. It 
 would seem probable that their differences are cor- 
 related with external conditions, and that it is these 
 which decide in what sequence they shall appear, 
 rather than any internal necessity. 
 
 Such a story of propagative method as this in 
 Ulothrix, combined with the similar facts which 
 result from the study of other allied forms, leads 
 to various general reflections. In the first place it is 
 seen that, in the cycle of life of Ulothrix or of Ulva, 
 two phases of existence appear. The one is stationary, 
 a condition imposed upon it by the fact that the living 
 protoplasm of each cell is encysted, that is confined 
 within a cell-wall, which makes free movement 
 
n] 
 
 THE BEACH AND ROCKS 
 
 23 
 
 impossible. This is the phase commonly known and 
 recognised as the plant, Avhich by growth and repeated 
 division of its cells may attain large size. The other 
 phase is one of freedom and active movement. The 
 
 Fig. 3. Ulothrix zonata. Showing production of gametes, A = 
 filament from which the gametes (sexual cells) are escaping, 
 B = a gamete, C, D = conjugation of gametes, in pairs, E = 
 zygospore, F= zygote, or result of fusion. G = germs produced 
 from it, Jf=a filament with germinating zoospores [z). 
 A, H, F and G x 200. 5—^x333. (After Klebs.) 
 
 protoplasm after division escapes from the restricting 
 cell- wall in the form of zooids, each capable of inde- 
 pendent movement in the water into which they 
 escape. From their minute size and their dependence 
 upon suitable external conditions for their escape and 
 
24 PLANT-LIFE ON LAND [CH. 
 
 movement they are apt to be overlooked. But there 
 is no doubt that there is a regularly recurrent phase 
 of motility in every completed life-cycle. It may 
 then be enquired which of these two phases, the 
 stationary plant or the motile zooid, was probably 
 the prior condition in evolution. 
 
 Among certain simple aquatic organisms called the 
 Flagellates minute forms exist which are always freely 
 motile, and have no fixed and encysted stage. Each 
 individual consists of a naked protoplast similar in 
 essentials to the zooid of Ulva or Ulothrix. This fact 
 suggests very strongly that the free and motile 
 condition was primitive, and that the encysted state 
 with a cell-wall surrounding each stationary protoplast 
 was later and derivative. The individual cells of the 
 Ulva plant are so minute that they are not seen 
 individually with the naked eye. But the obvious 
 Ulva plant is a large congeries of them. The cells 
 of the Flagellates are also individually small, but 
 being isolated they are invisible to the naked eye. 
 And so it is that while an ordinary visitor to the 
 sea-shore may be familiar with so obvious a plant as 
 Ulva, he will be unaware of the existence of its 
 propagative cells, as well as of its simpler unicellular 
 prototypes the Flagellates. This was for long the 
 position of Algologists also, and the view above 
 stated has emerged only in comparatively recent 
 times. The suggestion thus made for Ulva or 
 
 PROPERTY Of 
 
 imr A. &W. COLLEGE LIBRARYJ 
 
II] THE BEACH AND ROCKS 25 
 
 Ulothrix may be extended to other plants as well. 
 It may be stated as a general hypothesis that 
 primitive life was aquatic, and certainly one of its 
 forms, if not indeed a general form of it, was 
 free-swimming. The quiescent stage with encysted 
 protoplasts characteristic of the vast majority of 
 plants now living was probably derivative in many 
 cases, and perhaps in all, and owed its origin to 
 the convenience which it offers for protection, as 
 well as for self-nutrition and growth. If this be 
 true, then it is the derivative condition which we 
 commonly recognise as the "plant." 
 
 A second point for consideration relates to the 
 origin of sexualit}^ It has been seen that two 
 similar gametes unite in Ulothrix to form the 
 zygote. There is no differentiation of sex, though 
 the fusion is of the same nature as where such a 
 distinction exists. It would thus appear that some 
 process of fusion of cells antedated in descent the 
 distinction of sex. Further, the general similarity 
 in origin and form of the gametes and the zoospores 
 cannot escape remark. It would appear as though 
 the gametes were attenuated zoospores, a view Avhich 
 accords with their origin by further subdivision from 
 parent cells similar to those which form the zoospores. 
 It is possible that the fusion in such forms as these 
 originated as a means of strengthening the attenuated 
 zoospores. Again, comparison with the Flagellates 
 
26 PLANT-LIFE ON LAND [ch. 
 
 would support this hypothesis ; for in these plants 
 such fusions are absent, while the plant itself is 
 here of the nature of a zoospore. It thus appears 
 probable that the motile zoospore condition was 
 prior to such cell-fusions as the gametes undergo. 
 
 Thirdly, a comparison of Ulva or Ulotlwix with 
 other Green Algae, shows that inequality of size of 
 the gameteSj and ultimately marked differentiation 
 of the sexes, may appear. Such a progression from 
 equality to inequality of the gametes is seen also in 
 various types of the Brown Algae. From such facts 
 it may be concluded that the differentiation of sex 
 was acquired subsequently to the initiation of the 
 process of fusion, and that it was attained in several 
 different lines of descent. Its cause is probably to be 
 found in the advantage which a larger store of 
 nutriment brings to the germ. One type of gamete, 
 the male, retained its motility and approximately its 
 original size : the other, the female, became enlarged 
 and receptive, and ultimately it sacrificed its motility 
 to the advantage of better nourishment of the young 
 individual on germination. 
 
 It would be impossible here to do more than 
 suggest such views. The full discussion of them 
 must be left to larger works. But it will be apparent 
 that a study of the common Ulva and its related 
 forms, together with a comparison of other Algae 
 higher and lower in the scale, raises questions which 
 
II] THE BEACH AND ROCKS 27 
 
 are of prime importance as they affect the outlook 
 upon the vegetation of the earth. Guided by such 
 study we shall regard the condition of simple 
 organisms motile in water as primary ; the encysted 
 state of the protoplasm and the fixed position as 
 a secondary condition acquired as a concession to 
 nutritive convenience and mechanical protection ; 
 the process of sexual fusion itself appears also to 
 be secondary, originating perhaps as a method of 
 strengthening attenuated zoospores ; while, lastly, 
 the sexes were in the first instance alike, the differen- 
 tiation of the sexes having arisen subsequently to 
 the origin of sexuality. It probably arose in relation 
 to the necessity for adequate nutrition of the germ, 
 so that after fertilisation it may make an efficient 
 start in life, and successfully perpetuate its race. 
 
 Returning in conclusion to the Flora of the shore 
 as a whole, with its varied forms. Green, Brown, and 
 Red, they together with certain dwellers in fresh 
 water form a vegetation apart. These plants have 
 developed in accordance with their aquatic surround- 
 ings, and in their own way some of them have attained 
 a high complexity not only of form and construction, 
 but also of propagative method. But they always 
 bear the impress of their aquatic habitat, and differ 
 in essential features from the characteristic Flora 
 of the land. Their higher representatives may then 
 be regarded as being the culmination of their 
 
28 PLANT-LIFE ON LAND [ch. ii 
 
 evolutionary history. They are in fact "blind" 
 branches of the evolutionary tree. So far as any 
 relation can be traced between the Algae and 
 characteristic Land-plants this is to be sought for 
 among the simpler rather than the advanced types, 
 and even then the indications are of the slenderest. 
 But notwithstanding this, it is from the Algae that 
 we receive the clearest indications how plants at large 
 attained to many of the most fundamental features 
 that they show. The persistence of some of these 
 characters among Land-plants, even when their 
 presence is inconvenient, makes the conclusion in- 
 evitable that the origin of the vegetation of the earth 
 was ultimately aquatic. It probably sprang in the 
 first instance from free-swimming plants such as the 
 Flagellates, while the fixed Algae of our shores 
 represent an intermediate state, in which the quiescent 
 phase of self-nutrition had already become a constant, 
 as it is in them an obvious and indeed a preponderant 
 feature. 
 
CHAPTER III 
 
 THE BRACKEN FERN 
 
 A FEW miles along our coast there is a headland 
 backed by woods which stop short before the coast- 
 line is reached. The vegetation that runs down to 
 the beach is largely composed of the plants usual on 
 sandy shores, but they are accompanied by a quantity 
 of Bracken Fern which extends down almost to the 
 high-tide mark. Here and there the Bracken may be 
 so thick as almost to exclude any other plants. It 
 spreads backwards also into the woods, but there 
 various other Ferns make their appearance, and 
 these with the Bracken constitute a chief factor in 
 the undergrowth below the canopy of trees. 
 
 There are few plants that are so widely spread 
 over the earth's surface as the Bracken. It is the 
 most prevalent Fern here at home and is common 
 through Europe. It is seen on the high levels of 
 Ceylon, and has been noted as specially prevalent 
 at Singapore. It grows on the West Indian islands, 
 and though it is only sparingly present in South 
 
80 PLA:N^T-LTFE on land [ch. 
 
 America, it extends through the Southern Hemi- 
 sphere to New Zealand. It is true that in these 
 distant lands the type may differ from our own 
 Bracken in minor details, but the differences are 
 held to be only varietal, and the species designated 
 Pteridlum aquiliuiim — or better, known under its 
 old name of Pteris aquilina — may properly be recog- 
 nised as cosmopolitan. Where it occurs it is commonly 
 found in quantity, indeed it has been described by 
 Dr Christ as the gregarious Fern par excellence. 
 And so we see it sometimes growing with us so densely 
 as to occupy the ground to the exclusion of all else. 
 This is notably the case where the soil is sandy, and 
 free from lime. 
 
 Wading through Bracken as high as one's waist it 
 may be a surprise to be told that all that we see 
 above ground is the leafage, and that the stem which 
 bears the leaves is entirely concealed. But if you 
 take the trouble to dig the plant up you will i&nd 
 some inches below the surface of the soil an elongated, 
 horizontally running stock about half an inch in 
 diameter or less, dark brown in colour, and marked 
 laterally by two paler lines. From this the leaves 
 arise alternately on either side (Fig. 4). The growing 
 tip of the stock is covered with a dense mat of hairs, 
 and near to it one or two young leaves may be seen. 
 Further from the tip there will be found the stalks of 
 one, or at most two leaves of the current season whose 
 
Ill 
 
 THE BRACKEN FER^^ 
 
 31 
 
 blades are visible above ground. Furtliei* back again 
 are the stumijs of the leaves of earlier seasons, the 
 upper parts of them having decayed. The stock gives 
 rise to numerous roots, which are dark and wiry, and 
 extend in all directions. The whole shape of the 
 plant appears at first sight to differ strongly from 
 
 Fig. 4. Rhizome of Bracken Fern, showing the bases of successive 
 leaf-stalks (1 — 8) : No. 5 is the leaf of the j^receding season, 
 6 that of the current year, cut so as to show "King Charles' 
 Oak," 7 that of the coming season, and 8 a still younger one. 
 ss is the apex of the stock. Hoots run out in various directions 
 from the rhizome. (From Goebel, after Sachs.) 
 
 that of the densely tufted Ferns such as the Shield- 
 Fern {Nephrodium FUix-mas) ; but intermediate 
 conditions may be found between the two types of 
 shoot, which show that the difference depends merely 
 upon the degree of elongation of the axis : where 
 
32 PLA^N^T-LIFE ON LAND [ch. 
 
 this is short as in the 8hield-Fern the leaves appear 
 as a compact tuft, where it is long they are isolated, 
 while the stem may be either exposed to the air or 
 it may run underground as in PtericUum. 
 
 An examination of a number of rhizomes will show 
 that the stem is capable of indefinite growth in length, 
 but occasionally it forks at the tip into two exactly 
 equal branches. It is plain that by this means the 
 shoot-system may be enlarged, but a more effective 
 way is that which is more common in the Bracken, 
 viz. by the formation of a new bud near the base of 
 each leaf-stalk. Since each such bud is potentially 
 a new shoot endowed with apical growth like the 
 original, it is apparent that there are ample powers of 
 extension of the shoot-system. On the other hand, if 
 a stem be followed backwards from its apex, sooner 
 or later a region will be reached where the tissues 
 will be no longer fresh and living. The fact is that 
 decay is constantly progressing from the base upwards, 
 and whenever it extends beyond a bifurcation or the 
 insertion of one of the leaf-buds there will be a 
 complete severance of the two living apical regions, 
 and two individuals, physiologically independent, will 
 result. In this way the Bracken may spread over 
 large areas of ground, its development being simply 
 vegetative. In fact those large sheets of its growth 
 which occupy wide stretches of hillside and woodland 
 owe their origin to continued growth of individuals 
 
Ill] THE BRACKEN FERN 33 
 
 originally few in number. The underground position 
 of the stock makes for permanence of the individual. 
 During the austere time of our northern winter, or it 
 may be the drought of a southern summer, it contains 
 a liberal store of food-material laid up in its fleshy 
 tissues, ready for use in forming fresh leaves in the 
 coming season. This habit is naturally very effective 
 against extremes of climate. It has probably been a 
 factor in the success of the Bracken, as shown by its 
 commonness at home, as well as in its cosmopolitan 
 spread elsewhere. 
 
 The stately leaf of the Bracken is borne by the 
 upright leaf-stalk, which is dark coloured and hairy 
 where buried in the soil, but green and smooth above, 
 while paler lateral lines follow its course upwards. 
 It is here that provision is made for gaseous inter- 
 change with the outer air, which is elsewhere prevented 
 by a covering of hard woody tissue. It is this leaf- 
 stalk that children cut obliquely with a knife, and see 
 on the cut surface what they call " King Charles' 
 Oak " : the complicated arrangement of the conduct- 
 ing strands and of the brown tissue that accompanies 
 them being in outline roughly like a tree. In Germany 
 it is held to resemble the Double Eagle, and the name 
 " Adlerfarn" is accordingly given to it. High up on 
 this rachis the lateral lobes, or pinnae, are borne in 
 pairs, diminishing successively in size till the apex is 
 reached. The pinnae may be again branched, and 
 
 B. 3 
 
34 PLANT-LIFE ON LAND [ch. 
 
 the branching may be further repeated, so that the 
 whole leaf takes a highly divided form. The ultimate 
 ramifications widen out into green expansions which 
 collectively make up the lamina or region of the leaf 
 effective for self-nourishment. So well is this function 
 carried out that a large overplus of the material 
 gained is stored in the fleshy tissues of the under- 
 ground stock, and carried over as a physiological 
 balance to the ensuing season. 
 
 It is no wonder that a plant having the advantage 
 of a well-developed stock for storage, deeply buried 
 in the ground and so protected against risks from 
 climate as well as from animal attack, should succeed. 
 But in many districts, and especially in the North of 
 Scotland, its success is embarrassing to the farmer who 
 wishes to graze sheep, or to the forester who has to 
 plant out a hillside. To them the question is how to 
 extirpate it cheaply and effectively. The method in 
 common practice is physiologically sound. It is to mow 
 down the leaves about the end of June, that is so soon 
 as the leafage is approaching full development. The 
 process is to be repeated a second, or if necessary 
 a third year. Some may think that this succeeds 
 because the propagative spores, which as we shall see 
 are borne upon the leaves, are cliecked in their 
 development, and so their germination is prevented. 
 But it will be pointed out that the growth of new 
 plants through the germination of spores is uncommon 
 
Ill] 
 
 THE BRACKEN^ FERN 
 
 35 
 
 '**^^?^,r 
 
 -^^(^3^ . 
 
 Fig. 5. Leaf of the male Shield-Fern {Nephrodiwn Jilix-mas, Kieh.), 
 about one-eighth natural size, the lower part having the under 
 surface exposed. To the left a single segment, bearing the sori, 
 each covered by its kidney-shaped indusium. (After Luerssen.) 
 
 3—2 
 
36 PLANT-LIFE ON LAND [ch. 
 
 on the open hillside. The explanation of the success 
 of mowing about midsummer day is probably to be 
 found in its effect on nutrition. The plant has at that 
 time of year devoted all, or at least most of its 
 floating capital of stored food, to the business of the 
 formation of leaves and spores. But the leaves are 
 the nourishing organs, and they are mown before 
 their function is fully started. Thus the plant loses 
 the capital it has embarked. There may be a sufficient 
 residuum of stored food left to produce a second 
 or even a third formation of leaves ; but repeated 
 mowings will so deplete the rhizome as to lead finally 
 to death by starvation. 
 
 An observant friend in the Highlands has pointed 
 out to me that mowing is more efiective at low levels 
 where the growth is strong, than higher on the hills 
 where the Fern is relatively stunted. This is probably 
 to be explained by the fact that where growth of the 
 leafage of the year is favoured, the plant draws more 
 deeply on its floating capital than where the circum- 
 stances are less encouraging. The hill plants will 
 probably retain a larger proportion of their supply in 
 the underground stock, and so be better able to renew 
 the efibrt at leaf-formation. 
 
 But nutrition is not the only function of the 
 Bracken leaf. In fully matured plants theleaf also bears 
 the organs of propagation. If the ultimate branch- 
 ings of the leaf be carefully examined, it will be found 
 
Ill] THE BRACKEN FERN 37 
 
 that in many or even in most of them the margins 
 are curved downwards, and extended into a pellucid 
 veil or indusium, so that what appears from above to 
 
 Fig. 6. Vertical section through a fertile leaf, of Nephrodhim 
 traversing a single sorus. This is attached to one of the veins 
 of the leaf which is enlarged as the receptacle. Upon it are 
 seated the numerous stalked sporangia, each containing many 
 dark-walled spores. The whole is covered over by the umbrella- 
 like indusium. (After Kny.) 
 
 be the margin is really a curved and slightly swollen 
 region extending into a continuous protective fla[). 
 
38 PLANT-LIFE ON LAND [ch. 
 
 It is in the hollow of the curve thus formed that the 
 sporangia are inserted in large numbers, while a second 
 flap, less obvious than the first, forms a further 
 protection, the sporangia lying between the two. A 
 somewhat similar arrangement is seen in the common 
 Shield-Fern (Ne^^hrodmm filix-mas), but here the 
 sori, each covered by a kidney-shaped indusium, are 
 borne on tlie under surface of the leaf (Fig. 5). Each 
 of the sporangia is a stalked body with a capsular head 
 shaped like a biconvex lens (Fig. 6). Its margin is 
 occupied for three quarters of its length by a row 
 of hard cells forming the annulus, or spring by means 
 of which when ripe the sporangium opens and flicks 
 away its contents. It is inside these capsules that 
 the spores are produced, to the number of 48 in 
 each. When ripe they are dry and dusty, and being 
 very minute they may be blown to a distance by any 
 breeze. If a mature leaf be laid to dry face down- 
 wards upon a sheet of paper, a very perfect print of 
 its outline will in a short time be marked off* by the 
 spores which it will shed. Each spore is so small as to 
 be invisible to the naked eye, but they are conspicuous 
 collectively oAving to their vast numbers. A moment's 
 consideration is enough to realise the immense powers 
 of propagation with which the plant is endowed. 
 Each sporangium bears about half a hundred spores : 
 each minute subdivision of the leaf may produce very 
 many sporangia : the whole leaf is built up of a vast 
 
in] 
 
 THE BRACKEN FERN 
 
 39 
 
 number of such subdivisions, and the tracts of 
 Bracken may cover acres of ground. Calculations 
 based upon such facts soon reach figures which it 
 is beyond the powers of the mind to grasp : it must 
 suffice to say that the spores are produced in myriads, 
 
 Fig. 7. Nephrodium jiUx-mas. ^=prothallus seen from below. 
 ar = archegonia. a?i = antlieridia. r/t = rbizoids. jB = prothallus 
 with young Fern attached to it by its foot. 6 = the first leaf. 
 ti; = the primary root. ( x circa 8.) (After Strasburger.) 
 
 while each spore though consisting only of a single 
 cell bears all the powers and possibilities of a 
 potential life. 
 
 It is well to note that the spores are matured upon 
 leaves fully exposed to the air, and that dry circum- 
 
40 PLANT-LIFE ON LAND [CH. 
 
 stances favour their shedding. Moreover the Bracken 
 plant itself is well able to stand even considerable 
 drought. Thus not only is it an effective and success- 
 ful plant of the land, but dry conditions favour the 
 dissemination of the spores, the production of which 
 is the final office of the plant. 
 
 But such dry conditions do not suffice for the 
 further development of the spores. Nor do they 
 germinate directly into new Fern-plants, but into a 
 body called the prothallus, differing in texture and 
 in other qualities from the parent. Moisture and a 
 suitable temperature are necessary for its growth, 
 and it finally forms a flat green scale-like body, about 
 half an inch or less in diameter, and attached by 
 delicate root-hairs to the damp soil on which it grows 
 (Fig. 7, A). It is a physiologically independent body 
 capable of self-nourishment, but usually of limited 
 growth and duration. Its delicate texture makes 
 continued moisture a necessity for its growth, and 
 consequently it is found only in damp and shady 
 spots, where spores happen to have been carried as 
 loose dust by the breeze. This circumstance goes 
 far to determine the positions which Ferns habitually 
 hold in Nature, for as we shall see the Fern-plant 
 springs eventually from the minute green scale-like 
 prothallus. Sooner or later it bears the sexual organs 
 upon its downward surface, the male or antheridia 
 nearer the base, the female or archegonia nearer the 
 
Ill 
 
 THE BRACKEN FERN 
 
 41 
 
 indented apex. A succession of these is produced, 
 so that the possibility of carrying out their functions 
 may be spread over a considerable period. 
 
 When mature their condition is such that on 
 access of external fluid water, as when rain falls, 
 both of these organs, if ripe, burst. Naturally the 
 lower surface of the prothallus on which they are 
 
 Fig. 8. A. An antheridium of a Fern, mature and containing 
 numerous sperm -cells. C. A similar antheridium after rupture 
 and escape of the spermatozoids. B. A spermatozoid more 
 highly magnified, showing its spiral form during its movements 
 in water by means of the numerous thread-like cilia. (From 
 F. Darwin's Elements of Botany.) 
 
 borne will be moistened b}" any shower that wets 
 the soil thoroughly, and the rupture of such as are 
 ripe ensues. The male organs discharge their contents 
 as spermatozoids into the water, in which they 
 are capable of moving their spirally curled bodies 
 rapidly by means of the active lashings of numerous 
 cilia (Fig. 8). The female organs under similar 
 
42 PLANT-LIFE ON LAND [CH. 
 
 circumstances burst at the projecting tip (Fig. 9, B), 
 and an open channel then leads down to the egg, 
 which is deeply seated in the tissue (Fig. 9, C). 
 It might at first sight appear a matter of remote 
 chance that any individual spermatozoid should 
 enter an archegonium, but this is what may be 
 seen to occur with a high degree of certainty. The 
 explanation lies in the fact that the archegonium 
 gives out by diffiision into the water a very small 
 quantity of a soluble substance which acts as an 
 attraction to the spermatozoids. They move actively 
 from the weaker to the stronger solution, that is to 
 the neck of the archegonium, which is the centre of 
 the diffusion. One or more of them may enter the 
 neck, and passing down it one may be seen to fuse 
 with the egg-cell. This is the act of fertilisation, 
 which consists in the fusion of two cells, and 
 especially of their two nuclei ; for notwithstanding 
 its strange form the spermatozoid is actually a cell, 
 bearing a nucleus which forms the greater part of 
 its spiral body. The result of the fusion is a cell 
 called the zygote. It soon surrounds itself with a 
 cell-wall, and forms the starting point for the 
 development of a new Fern-plant similar to the 
 original parent. The embryo plant is nursed for a 
 time by the prothallus, upon which it lives as a 
 parasite while young. But soon it becomes inde- 
 pendent, rooting itself in the soil, and expanding 
 
Ill] 
 
 THE BRACKEN FERN 
 
 43 
 
 its young leaves to carry on the function of self- 
 nourishment. 
 
 It is very beautiful to note in young plants raised 
 by artificial culture how the underground habit of 
 the Bracken is started. The young seedling is in 
 its first stages like any ordinary Fern : but after 
 the formation of half a dozen or so of leaves the 
 
 B ^--^''^ C 
 
 Fig. 9. A. An archegonium of a Fern, approaching maturity. The 
 protective neck is closed at the apex. ?» = canal-cell. v.c.c.= 
 ventral canal-cell. o = ovum. B and C, similar archegonia quite 
 mature. The apex of the neck has ruptured, in both cases, and 
 the ovum (o) remains embedded in the prothallus {j)), while the 
 open channel of the neck leads down directly to it. (From 
 F. Darwin's Elements.) 
 
 axis bifurcates, and the two equal branches that 
 are formed curve strongly downwards, and bury 
 themselves in the soil. They never emerge again 
 from it in their normal life. Together with the 
 stores of nourishment laid up in their fleshy tissues 
 they are fully protected against extremes of climate, 
 as well as from animal attack. 
 
44 PLANT-LIFE ON LAND [CH. 
 
 The special efRcienc}^ in the Bracken is no doubt 
 in large measure due to this habit. It has been seen 
 how readily it spreads b}" the growth and profuse 
 branching of the underground rhizome. This serves 
 as a means of perennation from season to season. 
 It also serves as a place of storage of reserve food 
 for future use. So successful are these means of 
 perpetuation and of spread that little dependence 
 need be made upon the formation of new plants 
 by germination of the spores and sexuality. There 
 is many an observant botanist who has never seen 
 a young seedling of Pterklium in the open, and we 
 can only conclude that in Nature the completion 
 of the life-story by sexuality is a comparatively 
 rare event. There can be no doubt, however, that 
 the power of raising a young plant through the 
 germination of every matured spore is present, for 
 under conditions of suitable culture the prothallus 
 is easily grown, and young plants follow. 
 
 And thus the cycle of life of the Fern is completed. 
 It is plain that it consists of two distinct phases, or 
 generations as they are called, and the life-cycle is 
 punctuated by two periods when the organism consists 
 of only a single cell, viz. the spore which is produced 
 by the Fern-plant, and the zygote which is produced 
 by the prothallus. Between these landmarks intervene 
 two more extensive developments or generations, viz. 
 the prothallus and the Fern-plant. These succeed 
 
Ill] THE BRACKEN FERN 45 
 
 one another in a regular alternation. A produces B, 
 and then B again produces A : and so on. These 
 two generations differ widely in form and texture, 
 as also they differ in their water-relation. The 
 Fern-plant is structurally a land-growing plant, and 
 is capable of undergoing free exposure to ordinary 
 atmospheric conditions. Moreover dryness is essential 
 for the final end of its existence, viz. the shedding of 
 its spores. On the other hand the prothallus is 
 structurally ill fitted for exposure to dry air, while 
 fertilisation, which is the end of its existence, can 
 be achieved only in the presence of external fluid 
 water. 
 
 Fertilisation may rightly be held to be the most 
 critical event in the whole life of the plant. It has 
 doubtless been a phenomenon which has recurred in 
 every completed cycle of life of Ferns throughout 
 their long course of evolution. Its absolute depen- 
 dence upon the presence of water is then a fact 
 that cannot be lightly put aside. The same is also 
 found in all such plants as Liverworts, INIosses, 
 Horsetails, and Club-i\Iosses, as well as in the Ferns. 
 Now the plants named constitute a Land-Vegetation 
 which, on grounds of comparison as well as on the 
 evidence of the geological record, is rightly held to 
 be more primitive, and to be lower in the scale of 
 evolution than the Seed-bearing plants. They occupy 
 a middle place between these and the Algae. The 
 
46 PLANT-LIFE ON LAND [CH. 
 
 latter are typically aquatic, and their fertilisation is 
 usually carried out through the medium of the water 
 in which they live. We have seen examples of this 
 in Ulothrix and its allies. It therefore seems a 
 probable interpretation of the facts that long ago cer- 
 tain forms of Algae spread from the water to the land ; 
 that they retained signs of their aquatic ancestry both 
 in their method of fertilisation and in some measure 
 as regards the texture of the prothallus. Since the 
 final duty of the prothallus is the formation of the 
 sexual cells, or gametes, it is called the Gametophyte. 
 A second generation or phase, represented by the 
 Fern-plant, underwent special development to fit it 
 for more extended life exposed to the air on land. 
 It has as its final result the production of spores, and 
 it is accordingly called the Sporophyte. A Fern is 
 then an organism, so to speak, with one foot on land, 
 the other in the water. It indicates in the successive 
 events of its life-history a past migration from life in 
 water to life upon land-surfaces. The gametophyte 
 is the conservative phase which retains its aquatic 
 characters, the sporophyte is the innovation, which 
 has assumed characters more suitable to the adopted 
 habitat. Truly the life of such plants may be described 
 as amphibious. 
 
 We have seen that in the Fern the prothallus is 
 relatively small, while the Fern-plant is relatively 
 large. As we rise in the scale of vegetation to the 
 
Ill] THE BRACKEN FERN 47 
 
 Seed-plants, the same two phases are still found to 
 be represented in the life-story, but their disparity 
 becomes still more marked. Moreover the prothallus 
 in the higher plants no longer leads an independent 
 existence, but is enveloped in the tissues of the 
 sporophyte, upon which it lives as a sort of parasite. 
 As in other parasites the nutritive system, not being 
 necessary, is reduced. This reduction of the gameto- 
 phyte in the highest Flowering Plants attains to a 
 high degree. All that can be held to represent the 
 gametophyte in them is a body consisting of a few 
 rudimentary cells, which produce or minister to 
 the sexual gametes. Without pursuing these com- 
 parisons further, we may sum up the essential points 
 in one sentence and say that, in the higher Flowering- 
 plants the sporophyte is dominant, the gametophyte 
 is evanescent. In them the sporophyte generation is 
 what constitutes the obvious Plant-Life of the land, 
 while the gametophyte is so inconspicuous that to 
 the lay public it is a thing unknown. 
 
 The Fern-plant, though well able to hold its own 
 as a dweller on dry land, is after all an ill-differ- 
 entiated thing. Its primitive character is seen from 
 the fact that the leaf serves various purposes. Most 
 obviously it is an organ of nutrition as well as 
 of propagation. But as we rise in the scale of 
 organisation to the higher Seed-bearing plants 
 these two functions become separated, and localised 
 
48 PLA:N^T-LIFE on land [ch. Ill 
 
 in distinct regions of the plant. In fact the Flower 
 comes into existence as a thing distinct from the 
 merely vegetative shoot. The discussion of this will 
 be the subject of the ensuing chapters, in which it 
 will be shown that with the appearance of the Flower 
 the amphibious life is left behind, and a true Flora of 
 the Land is brought into being. 
 
CHAPTER IV 
 
 THE FLOWER AND METAMORPHOSIS 
 
 The end aimed at in the average flower-garden is 
 a succession of blooms as continuous as possible the 
 year through. Even in the open air it may be 
 managed that the garden shall never be actually 
 without them, though naturally the barest time is 
 in the dead of winter. The amateur gardener must 
 not only admire, but must also study to produce this 
 result ; and in doing so he will realise much more 
 fully than the casual lover of flowers that a period 
 of vegetative activity is a necessary prelude to that 
 of flowering. He will know that the very materials of 
 which flowers are made must be laboriously acquired 
 in all ordinary plants by self-nutrition, for Avhich the 
 green foliage is essential. In the annual plants of the 
 garden this is obvious enough. Germination of the 
 seeds of annuals in spring leads to the establishment 
 of the leafy plant, and it is only after this has attained 
 a certain development that flower buds make their 
 appearance, and finally the expanded blooms. These 
 
 B. 4 
 
50 PLANT-LIFE ON LAND [CH. 
 
 are formed at the expense of the materials which the 
 co-operation of the foliage-shoot with the root-s} stem 
 has been able to produce under the influence of 
 sunlight. But in the case of many of the plants that 
 expand their flowers in the winter or early spring the 
 matter is not so simple. We see the Snowdrop or 
 Crocus emerge from the soil, and we are apt to forget 
 the swollen underground parts fi'om which they 
 sprang, and from whose stores they drew their 
 sustenance. Still more are we unmindful of the 
 coarse leafage which, following on the flowers of 
 the preceding year, produced by its activity the 
 very materials which we see in the spring worked 
 up into the flowers that we prize. The fact that 
 those materials are stored up out of sight so long 
 before in the buried bulb or corm breaks the con- 
 tinuity of observation, and provides the excuse for 
 forgetting their existence. It is needless to elaborate 
 illustrations of the simple fact that nutrition must 
 precede propagation. However indirect the sequence 
 of events may seem, some form of vegetative shoot 
 precedes the flower with invariable constancy in the 
 individual life of the higher plants. 
 
 As in the preceding paragraph so in ordinary 
 conversation we distinguish the flower from the 
 foliage-shoot. But if we examine them both we 
 find that they have many features in common. In 
 both there is a stem, which bears appendages. More- 
 
IV] THE FLOWER AND METAMORPHOSIS 51 
 
 over the stem of the leafy shoot may be continued 
 directly upwards into the flower. Here, however, it 
 abruptly terminates, while in the leafy shoot it may 
 continue to grow indefinitely at the tip. The result 
 of this is that the flower is borne at the end of its 
 stalk. The relation of the appendages or leaves to 
 this stem is similar in the foliage-shoot and the 
 flower. In either case they arise laterally upon it, 
 and their succession is such that the oldest are 
 lowest down, and the youngest nearest to the tip. 
 In many cases the appendages are developed equally 
 all round the stem, giving what is called a radial form 
 to the shoot or flower, and this is believed to be 
 a relatively primitive condition. But both foliage- 
 shoots and flowers may be unequally developed, the 
 appendages growing stronger on one side than on the 
 other. This results in lopsided forms, and it can often 
 be shown that their lopsidedness originated as an 
 adaptation to meet special needs of the organism: 
 in fact it is regarded as a secondary modification in 
 the history of descent. The flowers of a Pea or an 
 Orchid will serve as illustrations of this. In these 
 cases the adaptation has been to fit them for the 
 insect visits which are essential for the process of 
 cross- pollination. Lastly, the parts of the flower are 
 as a rule closely aggregated together, Avhile those of 
 the vegetative shoot may commonly be separated by 
 intervals of the elongated stem. But all the leafy 
 
 4—2 
 
 I 
 
52 PLANT-LIFE ON LAND [CH. 
 
 shoots terminate in a compact aggregate of leaves, 
 which is called a bud : and so, at least in the young 
 state, the vegetative shoot may resemble the flower 
 so far as the aggregation of its parts is concerned. 
 
 It thus appears that there are marked analogies 
 between the foliage-shoot and the flower. This leads 
 to the question whether there is any absolute diflference 
 between them. It will lie near to the hand to suggest 
 the qualities of texture of the parts, of their colour, 
 or their scent, by which flowers are apt to be charac- 
 terised as distinct from vegetative shoots. But 
 none of these are constant features in the one or 
 entirely absent from the other. There is, however, 
 one absolutely distinctive character. It is the 
 presence in the flower of the organs of propagation 
 called "sporangia." These are of two sorts, on the 
 one hand the ovules which mature into the seeds, on 
 the other the pollen-sacs which produce the pollen. 
 It is the presence of either or both of these which 
 stamps the flower as distinct from a foliage-shoot 
 (Fig. 10). 
 
 However different these two essential organs of 
 the flower, the ovule and the pollen-sac, may seem to 
 be to day, there is good reason for holding them to 
 be modifications produced in descent from a single 
 primitive type of sporangium. This organ had as 
 its office the production of spores or separate germs 
 shed from the parent. In the more primitive plants 
 
IV] THE FLOWER AND METAMORPHOSIS 53 
 
 these were all alike, as were also the sporangia 
 which contained them. Such a condition is still seen 
 in the Ferns, Club-Mosses, and Horsetails of the 
 present day. It is held that sporangia essentially 
 similar to theirs were modified in the course of 
 descent, in accordance with the differentiation of sex, 
 
 Fig. 10. Median section of the flower of a Butteicui^, showing its 
 constituent parts. On the outside (lowest down in the drawing 
 and shaded) are the sepals of the calyx: within this the large 
 petals of the corolla of which three are shown : within this and 
 seated higher on the axis are the numerous club-shaped stamens, 
 each of which bears four pollen-sacs. Centrally in the flow^er are 
 the numerous carpels, one of which is dissected so as to show its 
 single ovule, or future seed. (From Le Maout and Decaisne.) 
 
 until they finally assumed those two apparently 
 different forms, the pollen-sac and the ovule. It is im- 
 portant for our enquiry into the relation of the flower 
 and the foliage-shoot that this correspondence of the 
 ovule and the pollen-sac with the sporangia of Ferns 
 and Club-Mosses should be realised. Its acceptance 
 
54 PLANT-LIFE ON LAND [ch. 
 
 makes it possible to compare the regions of the plants 
 in which those organs occur ; that is, to compare the 
 flower of the higher plants with the fertile region of 
 Ferns or Club-Mosses. It is upon such comparisons 
 that it will be found possible to base an opinion as 
 to the true relation of the flower to the foliage region, 
 and to understand the underlying similarity of con- 
 struction which they show. 
 
 The obvious analogies which exist between the 
 flower and the foliage-shoot in the higher plants did 
 not fail to attract the attention of some of the early 
 observers. Wolfij in his Teoriageuerationis, published 
 in 1759, wrote that "In the whole plant whose parts 
 we wonder at as being at the first glance so extra- 
 ordinarily diverse, I finally perceive after mature 
 consideration and recognise nothing beyond stem 
 and leaves.... Consequently all the parts of the plant 
 except the stem are modified leaves." Not many 
 years later the poet Goethe elaborated this general 
 conclusion into the theory of "Metamorphosis," which 
 is associated with his name. He recognised as 
 Metamorphosis the process by which one and the 
 same organ, for instance the leaf, presents itself to 
 us in various modifications, such as the foliage leaf, 
 sepal, petal, or stamen. He then went on to 
 distinguish as examples of "progressive metamor- 
 phosis" those changes of type of the appendages 
 which proceed from the cotyledons or seed-leaves 
 
IV] THE FLOWER AND METAMORPHOSIS 55 
 
 through the foliage region and the bracts to the 
 flower, and finally to the perfected fruit. He noted 
 the modification of one form into another in a regular 
 succession, till the " acme of Nature " is reached in 
 reproduction by seed. On the other hand he designated 
 as "retrogressive metamorphosis" the process by 
 which that succession appears to be reversed, as 
 for instance in abnormal or doubled flowers, when a 
 stamen or a carpel developes as a petal, or even as 
 a foliage leaf. Lastly, he styled as "irregular or 
 accidental metamorphoses" those changes of the 
 normal parts which often follow upon the attacks 
 of insects, or other external agents. These general 
 ideas of the relation of the vegetative and floral 
 regions were amplified and made more definite by 
 subsequent writers, and were for a long time widely 
 held. Thus it became a general belief that the flower 
 had resulted from changes wrought in some pre-ex- 
 istent vegetative shoot. 
 
 So long as we direct our attention solely to the 
 Seed-bearing (or Flowering) plants, and are prepared 
 to pass lightly over all comparisons with Vascular 
 plants lower in the scale, this opinion may stand. 
 But as the 19th century drew on, the knowledge of 
 the lower forms was greatly widened, especially in the 
 case of such plants as the Ferns and Club- Mosses. 
 This supplied the material necessary for a revised 
 theory of the origin of the flower. Moreover, about 
 
56 PLANT-LIFE ON LAND [CH. 
 
 the middle of the 19th century, views of descent 
 began to make their influence felt upon the study of 
 form in plants. But it was only slowly that this 
 became apparent in a fuller knowledge of the genesis 
 of the flower of the higher plants. Consequently it 
 has only been in recent decades that the acceptance 
 of the flower as the result of metamorphosis of a 
 vegetative shoot has ceased to satisfy. It will be 
 well to explain the reasons for the change. 
 
 In a previous chapter (p. 44) it has been shown 
 that the life-story of a Fern consists of two phases, 
 the relatively small green prothallus and the relatively 
 large spore-bearing Fern plant. It was Hofmeister 
 who first recognised that a similar alternation of two 
 such phases is characteristic of all Vascular plants, 
 including all those which bear flowers. In all of them 
 that obvious thing which we call " the Plant " is the 
 spore-bearing generation, and its end is the forma- 
 tion of sporangia and spores. What we are now 
 considering is the evolutionary relation of the sterile 
 and fertile regions of such plants. 
 
 In every normally completed life of Vascular plants 
 sporangia are formed. This is so in all living Ferns, 
 Club-Mosses, and Horsetails, as well as in Seed-bear- 
 ing plants. Moreover the evidence of the fossils 
 shows that it was the same with the related plants of 
 the distant past. Hence we may conclude that it has 
 been so throughout their descent. If this be true, 
 
IV] THE FLOWER AND METAMORPHOSIS 57 
 
 then the origin of the Flower, and particularly of 
 those sporangial organs which are its distinctive 
 feature, cannot have been an afterthought. They 
 cannot ever have been superposed upon a pre- 
 existent vegetative system. And this must still be 
 true notwithstanding that in the life of any ordinary 
 plant the vegetative leaves appear first. The Flower 
 cannot have been a mere result of metamorphosis of 
 a vegetative shoot, for it represents a phase which has 
 grown up together with the rest of the plant, and has 
 been an integral part of its completed life through- 
 out descent. Those who realised this to the full were 
 at first disposed to invert the theory as stated by 
 Goethe and his followers. Instead of holding that 
 the flower was really a vegetative shoot adapted for 
 propagative duties, they were disposed to assume that 
 the whole plant had originally been propagative, and 
 that the vegetative system had originated by sterili- 
 sation of certain of its parts. It was suggested that 
 such sterile parts were then told ofi^ to purposes of 
 nutrition as a new duty. JMoreover, experimental 
 evidence from the Ferns seemed to tend directly 
 towards this conclusion, for it was found possible 
 experimentally to transform fertile leaves of Ferns 
 into sterile leaves, with abortion of the sporangia. 
 This seemed essentially parallel with the transforma- 
 tion of stamens into petals, or carpels into green leaves, 
 as is seen in some " doubled " flowers. 
 
58 PLANT-LIFE ON LAND [ch. 
 
 It is by no means outside the bounds of possibility 
 that this theory of sterilisation may be near to the 
 ultimate truth. But at present we are not in a 
 position to look Avith any certainty so far back as to 
 the ultimate origin of either the vegetative or the 
 propagative system of the spore-bearing plant. A 
 third view which does not raise questions of ultimate 
 origin has, however, been suggested by a comparison 
 of the simpler Vascular plants. It appears to stand 
 upon a sound basis of fact and of logical reasoning, 
 for it starts not from any hypothetical forms, but 
 from such plants as we can see living to day. It is 
 that the whole shoot of relatively primitive Vascular 
 plants was non-specialised : it served as a general- 
 purposes shoot. Both functions had to be performed 
 by it in earlier times. But in the course of evolution 
 of higher types differentiation took place, so that a 
 certain region became specially developed to carry 
 on nutrition, another region of the shoot produced 
 spores. The result of this is that the two functions 
 are carried out by distinct regions of the shoot 
 specially developed for the purpose. The vegetative 
 region habitually comes first in the individual life, 
 the propagative region, or " flower " as it is called in 
 the higher plants, appears only late after the plant 
 has acquired sufficient material for the formation 
 of the propagative organs. It is by comparison 
 of Seed-plants with the lower Vascular plants that 
 
ivj THE FLOWER AND METAMORPHOSIS 59 
 
 ■•*i:5-,'fftv;. 
 
 ^;:-^^'>.,^ 
 
 -^i^^f^ 
 
 % 
 
 ''<^f^^^' 
 
 * "^^ 
 
 m0^ 
 
 ^»WW0^:: 
 
 """mm. 
 
 Fig. 11. Leaf of the male Shield-Fern [N eplir odium filix-mas, Eich.), 
 about one-eighth natural size, the lower part having the under 
 surface exposed. To the left a single segment, bearing the sori, 
 each covered by the kidney-shaped indusium. (After Luerssen.) 
 
60 PLANT-LIFE ON LAND [ch. iv 
 
 evidence may be obtained of the correctness of this 
 view. 
 
 Two common plants, which are widespread in 
 Great Britain, may be cited as illustrative examples, 
 viz. the Common 8hield-Fern {Nephrodium filix- 
 Qiias), and a common Club-Moss {Lijcopodiimi Selago). 
 In the former the plant consists of a simple shoot 
 bearing leaves which are all alike, but large and 
 freely branched. Though in young plants the leaves 
 bear no sporangia, in any well nourished plant that 
 is mature all the leaves are as a rule fertile. They 
 are in fact leaves that serve various purposes, for 
 when young they protect the tender apical bud, and 
 when expanded they serve the double purpose of 
 nutrition and of propagation by spores (Fig. 11). But 
 in Flowering plants these three functions are generally 
 carried out by three different types of leaves, the 
 scale-leaves protecting the bud, the foliage leaves 
 serving for nutrition, and the stamens and carpels 
 for propagation. In some Ferns these distinctions 
 are already suggested ; for instance, in the common 
 Hard Fern {Lomaria sjncaut) the sterile and fertile 
 leaves diifer in outline though fundamentally alike : 
 and in the Royal Fern {Osmnuda regalls) there are 
 some stunted leaves Avhich serve for protection only. 
 Such occasional distinctions seem to suggest that 
 our hypothesis of differentiation is really a correct 
 one. 
 
Fig. 12. Plant of Lycopodium Selago, showing on its several axes 
 alternating sterile and fertile zones. This is best seen about 
 half-way up the specimens. The leaves are alike in both ; the 
 difference lies in tbe absence of the sporangia from the sterile 
 zones. (Slightly reduced.) 
 
62 PLANT-LIFE ON LAND [CH. 
 
 In the Common Club-Moss {Lycopodium Selago), 
 after an initial vegetative growth in which all the 
 leaves of the young plant are sterile, the shoot settles 
 down to a condition which is shown in Fig. 12. The 
 small and simple leaves appear all alike in size and 
 texture, being clearly nutritive in function. The 
 whole shoot is uniform throughout its length, except 
 that it is marked off into successive zones which are 
 alternately sterile and fertile. In the former a single 
 sporangium is present in the axil of each leaf : in the 
 latter the sporangia are absent. But at the limits of 
 the fertile zones there are smaller abortive sporangia, 
 while occasionally an isolated sporangium, or two or 
 three of them, may be found within an otherwise 
 sterile zone. When it is remembered that spore- 
 production was constant throughout descent, such 
 facts point very directly to the conclusion that there 
 existed at first a shoot which was both initritive and 
 propagative, and that this Club-Moss shows those 
 functions only partially separated, the sporangia 
 being imperfect or entirely suppressed in the sterile 
 zones, while the fertile zones maintain their pristine 
 state. But in the great majority of the Club-Mosses 
 the sporangia are associated with the leaves at the 
 end of the shoot only, forming a cone or strobilus. It is 
 plain that in them the differentiation has been carried 
 out more perfectly. Such cones are the prototypes 
 of Flowers, while the sterile region below represents 
 
IV] THE FLOWER AND METAMORPHOSIS 63 
 
 the foliage as seen in the higher Seed-plants. So far 
 then from the Flower being the result of " Metamor- 
 phosis " of a vegetative shoot, as the theory of Goethe 
 maintained, it appears more probable that both arose 
 from a common source. If any transformation or 
 "metamorphosis" has occurred, it was probably a 
 conversion of leaves which were primitively fertile 
 into a sterile state, by abortion of the sporangia 
 Avhich they bore. And we have seen that this change 
 can be brought about experimentally even at the 
 present day. But that is the direct opposite of what 
 was designated by Goethe as "progressive meta- 
 morphosis." It may perhaps be called with more 
 propriety " Sterilisation," a term which indicates 
 clearly what has probably been a prevalent pheno- 
 menon in the course of descent of Vascular plants. 
 Quite recently a direct support for such opinions 
 has been supplied by the discovery and description 
 of the flowers of the fossil Bennettitales. These, as 
 also the modern Cycads to which they were allied, 
 were linked by many characters to the Ferns : but on 
 the other hand they produced seeds resembling in 
 certain essential points those of the modern Pines, 
 and Larches, etc. These Cretaceous and Jurassic 
 plants showed a decidedly Fern-like character of 
 the staminal leaves, while the centre of the floAver 
 was occupied by seed-bearing structures forming col- 
 lectively a sort of pistil (Fig. 13). Such flowers were 
 
64 PLANT-LIFE ON LAND [CH. 
 
 borne on the ends of lateral branches, and terminated 
 their growth just as those of Seed-plants do nowa- 
 days. The foliage resembled that of the present-day 
 Cycads. The most interesting point in these flowers 
 as bearing on our present discussion is the similarity 
 of their stamens to the fertile leaves of certain Ferns. 
 The view which may be taken of these primitive 
 flowers is that they represent a region of the Fern- 
 like shoot which has retained its function of pro- 
 pagation, while the region below is sterile and is 
 developed to carry on the other pristine function of 
 nutrition. 
 
 Such an example as this indicates the origin of 
 the propagative organs at the centre of the flower. 
 But so far no explanation has been given of the origin 
 of the outer envelopes, — the calyx and corolla : nor 
 is there any certain knowledge how they came into 
 being. It may be that they originated in difierent 
 ways in the various groups of plants. In some cases 
 it seems probable that the calyx sprang from bract- 
 like leaves of the vegetative region already sterile, 
 which became specialised for a protective duty. On 
 the other hand, the corolla in certain cases was 
 probably derived from the outermost stamens which 
 became diverted from their specific function as pro- 
 pagative organs to the duty of attraction of insects 
 by colour, scent, and honey -secretion. By such means 
 a further step of sterilisation appears to have been 
 
Fig. 13. Restoration of an unexpanded bisporangiate strobilus, or 
 flower, of Cycadeoidea, with part of the enveloping hairy bracts 
 removed. The unexpanded fronds of the staminate disc are 
 curved inwards, and show the reduced fertile pinnae. At the 
 centre is the apical cone covered by short-stalked ovules and 
 inter-seminal scales. About natural size. (After Wieland.) 
 
 B. 5 
 
66 PLANT-LIFE ON LAND [ch. 
 
 effected subsequent to the earlier segregation of the 
 nutritive from the propagative regions of the shoot. 
 
 Thus we may figure to ourselves how the flower 
 as distinct from the vegetative region originated in 
 the higher plants. The main point to bear in mind 
 is that the propagative function recurred in each fully 
 completed life-cycle throughout descent. It was 
 never an innovation. The propagative organs can- 
 not at any time in descent have been superimposed 
 upon a pre-existent vegetative system. Their appear- 
 ance may have been deferred in the individual life, and 
 it is only natural that the nutritive phase should pre- 
 cede the propagative, since food-material is necessary 
 for the latter process. But however long the nutritive 
 phase might be, or however prominent the organs 
 which carry it out, the propagative phase supervenes 
 sooner or later in every completed life. All evidence 
 points to the belief that it was represented throughout 
 the course of evolution. 
 
 Once the two pristine functions were allocated 
 to distinct regions of the shoot, these were open each 
 to its own distinct specialisation, and thus they became 
 fitted for their respective duties. And so it comes 
 about that while in simple cases there may be some 
 similarity, between the flower and the foliage-shoot, 
 as for instance in Magnolia, which is on that account 
 held to be a relatively primitive type of Flowering 
 plant, the two may diverge widely in their characters 
 
IV] THE FLOWER AND METAMORPHOSIS Q7 
 
 in more advanced types, as do the foliage and flowers 
 in such plants as the Orchidaceae. But however 
 greatly they may differ, we must still hold the flower 
 and the vegetative shoot to be the ultimate con- 
 sequences of segregation of parts of the same original 
 type of shoot, to serve the two fundamental and 
 constant duties respectively of propagation and 
 nutrition. This is the most natural interpretation 
 of those structural resemblances, which are so obvious, 
 between the foliage-shoot and the flower which it 
 ultimately bears. There is no need now for any 
 theory of metamorphosis to explain the origin of the 
 Flower. As first stated by Goethe it was a theory of 
 mysticism, which was doomed to dissolution so soon 
 as the disclosure of the necessary facts made com- 
 parative study possible. 
 
 5—2 
 
CHAPTER V 
 
 POLLINATIOJS^ AND FERTILISATION 
 
 By many of those who write for the general public 
 Pollination and Fertilisation are used as synonymous 
 terms. This may have been natural when, over a 
 century ago (1/93), Sprengel published his novel obser- 
 vations under the title of Das entdechte GeJieimniss 
 der Natiir im Bau und in der Be/ruclitung der 
 Blumen (The Secret of Nature discovered in the 
 Structure and Fertilisation of Flowers). But at the 
 present day there is little excuse for such laxity. 
 Even MUller's classical work appears in its English 
 edition under the title of The Fertilisation of Flowers 
 hij Insects. And yet on opening it we find that it 
 deals throughout with the transfer of pollen, and 
 the actual detail of the act of fertilisation is not 
 mentioned. It is well to be clear at the outset as 
 to the correct use of these words when applied to 
 the Higher Flowering plants. By pollination is 
 meant merely the transfer of pollen from the anther, 
 where it is produced, to the receptive surface of 
 
CH. V] POLLINATION AND FERTILISATION 69 
 
 the stigma (Fig. 15, p. 73), where it is to develope 
 further. By fertilisatiou is meant the actual coales- 
 cence of two cells, the one derived from the develop- 
 ment of the pollen-grain, that is the male cell, the 
 other contained within the ovule or future seed, that 
 is the female cell. It will be at once apparent that 
 some interval of time must elapse between the two 
 events of pollination and fertilisation, an interval 
 which is usually short, but may in extreme cases be 
 as long as a year, or even more. Pollination in the 
 Flowering plant precedes fertilisation, and is a means 
 to that end, but fertilisation is the end itself 
 
 It is not the object here to detail the various 
 methods by which pollination is secured. The chief 
 facts are already available in many published works, 
 some of them written for scientific, others for popular 
 readers. In all of them the importance of inter- 
 crossing is brought forward, involving the transfer 
 of pollen from one individual to another, a process 
 which brings with it definite racial advantages. The 
 specialisation of the fertile region of the shoot for 
 this purpose is as varied as it is often beautiful. The 
 very genesis of the forms of flowers, their tints, and 
 scents is in strict accordance with their efficiency as 
 pollinating mechanisms. Our own aesthetic pleasure 
 in them is purely subjective. It must not be permitted 
 to blind us to this simple fact. At the same time we 
 see that the expenditure of material in the production 
 
70 PLANT-LIFE ON LAND [ch. 
 
 of flowers is great. This should impress weightily 
 upon the mind the importance which attaches to 
 intercrossing. 
 
 Due recognition is readily given in popular books 
 to the wonderful mechanisms by which intercrossing 
 is carried out. But it often happens that the actual 
 process of fertilisation, as it is efiected in the Higher 
 Flowering plants, is left entirely out of account. Its 
 main features are, however, of the highest importance 
 as giving material for comparison leading to broad 
 views of descent. It will therefore be necessary to 
 recount how fertilisation is carried out in an ordinary 
 Flower. A basis of comparison will thus be provided 
 with plants lower in the scale. 
 
 The stamen is an organ which usually bears four 
 pollen-sacs. Each contains many pollen-grains, which 
 are set free by rupture of the protecting wall. The 
 grains are commonly dry and dusty, but incapable of 
 spontaneous movement : so that each is independently 
 open to transfer by external agencies. The numbers 
 of the grains are roughly in relation to the precision 
 of the removing agent. Where the method is hap- 
 hazard, as in the case of transfer by the wind, the 
 production of pollen is usually profuse. Where the 
 method is exact, as in the case of insect-agency 
 working in relation to a highly specialised flower, 
 the production of pollen is limited. Extreme cases 
 of economy are seen in Orchis where a single stamen 
 
V] POLLINATION AND FERTILISATION 71 
 
 suffices for the requirements, or Salvia (Sage), where 
 two half-stamens achieve the end. In either case 
 the flower-mechanism for making use of the visits 
 of certain insects is a peculiarly perfect one. 
 
 The pollen-grain itself is protected externally by 
 a wall often thick, variously sculptured, and coloured. 
 
 Fig. 14. Pollen-grain of Lilium Martagon, and its germination, 
 k — nucleus of the large vegetative cell of the pollen-tube : m = 
 small mother-cell of the antheridium : ^ = generative cells, or 
 male gametes. ( x 375.) (From Strasburger, after Guignard.) 
 
 Within are found at the period of ripeness two cells, 
 each with a nucleus (Fig. 14). The larger cell is 
 styled the vegetative cell, and it takes no direct part 
 in fertilisation. The smaller is called the antheridial- 
 mother-cell. It consists of rather dense protophism 
 
n PLANT-LIFE O:^ LAND [ch. 
 
 surrounding a nucleus. It is from this cell that the 
 gametes or male cells are derived. 
 
 The gynoecium or pistil occupies the centre of 
 the flower. It consists in a simple case of the parts 
 shown in Fig. 15. The lower enlarged region is 
 the ovary, the wall of which {fw) protects a single 
 straight ovule. The ovary is continued upwards into 
 a narrower region of the style {g), and is enlarged at 
 the tip into the receptive stigma {n\ It is here 
 that the pollen is received, and retained upon the 
 roughened and often sticky surface. The ovule thus 
 enclosed in the cavity of the ovary consists of a 
 short stalk {fu\ bearing the body of the ovule. 
 From the upper limit of the stalk arise two over- 
 lapping integuments (/^, ii)^ which closely invest the 
 massive nucellus {:)i\i). This is an oval body of tissue 
 enveloping the large embryo-sac (e), which has 
 complicated contents. The most important of them 
 is the ovum, or ^g^, which is the largest of three 
 cells forming a group called the egg-apparatus (e^), 
 which is fixed at the uppermost end of the embryo-sac. 
 The ovum is a primordial cell, that is, it has no 
 cell-wall, and consists of cytoplasm with a nucleus. 
 It is the female cell, and it developes no further unless 
 fertilised. 
 
 The sexual cells or gametes are thus produced 
 apart from one another. The problem is to bring 
 them together when neither is motile, and one is 
 
V] POLLINATION AND FERTILISATION 73 
 
 deeply enveloped in protective coverings. The usual 
 isolation of the pollen-grain allows of its free transfer, 
 and the varied mechanisms of flowers secure that the 
 
 Fig. 15. Ovai-y of Polygonum convolvulus during fertilisation, fw — 
 wall of ovary : fs = stalk-like base of ovary : fu = funiculus : cha = 
 chalaza : m^ = nucellus : mi = raicropyle : // = inner, ?> = outer 
 integument : <3 = embryo -sac : efc = central nucleus of embryo-sac : 
 ei = egg-apparatus : an = antipodal cells : g = style : n = stigma : p = 
 pollen-grains: _/96 = pollen-tubes, (x48.) (After Strasburger.) 
 
74 PLANT-LIFE ON LAND [ch. 
 
 pollen shall be landed upon the surface of the stigma 
 (Fig. 15, p. 73). Thus the more hazardous part of the 
 journey is accomplished, with or without intercrossing. 
 Then begins the further development of the pollen- 
 grain. A delicate tube grows out from it, which 
 penetrates the tissue of the style, and makes its 
 way downwards to the cavity of the ovary. Finally, 
 it reaches the apex of the ovule, and comes into 
 close contact with the egg-apparatus. This tube 
 conveys the contents of the pollen-grain, so that the 
 transfer to the deeply seated egg, otherwise difficult, 
 is readily accomplished. When the germination of 
 the pollen-grain upon the surface of the stigma 
 begins, the contents of the grain pass into the 
 tube. The antheridial cell divides into two gametes 
 (g, Fig. 14), and these preceded by the vegetative 
 nucleus {k, Fig. 14), maintain a position near to the 
 apex of the tube as it grows. Finally, on reaching 
 the embryo-sac, the nucleus of one of the gametes 
 enters the ovum, and fuses with its nucleus. This is 
 the essential point in fertilisation. The resulting cell, 
 or zygote, forms the starting-point for development 
 of the new individual. Since the nucleus is believed 
 to be the bearer of hereditary qualities, the zygote 
 will have received those of both parents, so far as 
 they are conveyed by the nuclei which coalesce ; 
 and those qualities will pass on to the newly produced 
 offspring. 
 
V] POLLINATION AND FERTILISATION 75 
 
 It is well to bear in mind that the event of 
 fertilisation is probably the most critical in the 
 whole life-story. There is no doubt that it figured 
 in an equally critical way throughout evolution, and 
 was a crisis in each completed life-cycle. 
 
 It is then right and fitting that a premier place 
 should be given to the comparison of methods of 
 fertilisation in discussions on descent. At first sight 
 there may seem to be little relation between the 
 propagative method of a Flowering plant here 
 described and that of a Fern already detailed in 
 Chapter III. So long as the external features only 
 are noted the divergence appears to be a wide one. 
 It is only when the details are followed out that an 
 essential similarity appears. As a matter of fact an 
 adequate knowledge of the propagative process in 
 Ferns long preceded that of the corresponding events 
 in the Flowering plants. It remained for modern 
 methods of preparation to show how the nuclei 
 behave, and it is upon this that the whole comparison 
 turns. We now know that in the fertilisation of the 
 Fern, just as much as in that of the Flowering plant, 
 the essential point is the coalescence of two cells, 
 and especially of the nuclei of two cells, which are 
 more or less distinct in their origin. In the Fern 
 the spermatozoid conveying the male nucleus makes 
 its own way to tlie nucleated ovum. In the Flowering 
 plant the male gamete is non-motile and is handed 
 
1^ PLANT-LIFE ON LAND [ch. 
 
 on passively by the pollen-tube to the ovum. The 
 detail of method differs in the two cases, but the 
 essentials are the same in both. 
 
 Having thus recognised their fundamental likeness, 
 it lies open to us to enquire whether the differences 
 afford any ground for opinion as to descent? The 
 main difference between the two processes lies in the 
 medium of transfer. In the Fern the spermatozoid 
 moves in water, and external fluid water is necessary 
 for fertilisation. In the Flowering plant it is not. 
 The formation of the pollen-tube and its conveyance 
 of the male gamete to the Q.^g may be carried out 
 without reference to external fluid water. It commonly 
 occurs in dry summer weather, and is only dependent 
 on water so far as the whole plant is so dependent for 
 carrying out its ordinary functions. In this respect 
 then the Flowering plant may be said to be essentially 
 a plant of the Land. The Fern, though capable of 
 vegetating on the Land, is dependent at a most 
 critical moment on external water. In this it reveals 
 an amphibious character. 
 
 But a further question which has its immediate 
 bearing on descent is whether there is evidence of 
 transition from one of these types to the other. As 
 the Ferns show many relatively primitive characters 
 both in structure and development this question will 
 present itself only in one way. Is there any evidence 
 of a transition from the aquatic fertilisation by 
 
V] POLLINATION AND FERTILISATION 11 
 
 sperinatozoids to the terrestrial method by a pollen- 
 tube? A certain degree of probability that such a 
 change had taken place was derived long ago from 
 the general comparison of the propagative methods 
 in Ferns and Flowering plants. But the demon- 
 stration of spermatozoids still surviving in some 
 
 Fig. 16. Zamia floridana. Distal end of the pollen-tube, showing 
 the vegetative prothallial cell {v), the sterile sister-cell (.s) and the 
 two spermatozoids. a, before movement of the spermatozoids 
 has commenced ; h, after the beginning of ciliary motion : the 
 prothallial cell is broken down, and the separation of the two 
 spermatozoids is taking place. ( x circa 75.) (From Strasburger, 
 after H. J. Webber.) 
 
 Seed-bearing plant would naturally appear more 
 conclusive than such comparisons could possibly be. 
 Some botanists had long been expectant that instances 
 of this would eventually be found. The expectation 
 has now been realised in the case of two ancient 
 
78 PLANT-LIFE ON LAND [ch. 
 
 families of plants belonging to the Gymnosperms. 
 Such plants, as their name implies, show their primi- 
 tive character by bearing their seeds exposed, as in 
 the Pine or Yew, and not contained in a seed-vessel, 
 like the more advanced Flowering plants. It is in 
 the Cycads and in the Maiden-hair Tree {Ginlgo) that 
 fertilisation by motile spermatozoids has been found 
 to occur. In both cases the pollen-grain germinates 
 essentially as in other Flowering plants. But the 
 gametes which each produces, instead of being passive, 
 are motile, by means of cilia, in fluid extruded into 
 a hollow chamber at the apex of the ovule : and thus 
 access is gained to the egg (Figs. 16, 17). The con- 
 clusion which follows from such facts is unavoidable. 
 The condition of the Cycads and Ginkgo can only be 
 held to be vestigial ; moreover the motility of their 
 gametes is of little practical use. The gametes of the 
 higher Flowering plants must then be regarded as 
 spermatozoids which have given up this unnecessary 
 motility, and become passive. Thereby they have 
 parted with the last indication of their pristine mode 
 of fertilisation by means of gametes freely swimming 
 in water, and show full accommodation to life upon 
 Land. But the Cycads and Ginkgo -still show traces of 
 their amphibial origin. The rest of the Seed-plants, 
 however, now constitute a true Flora of the Land, 
 characterised as such by their complete independence 
 of external fluid water as a medium for fertilisation. 
 
V] POLLINATION AND FERTILISATION 79 
 
 The importance of the step thus taken is very 
 great. The most convincing indication of it is seen 
 in the numerical richness of the types which have 
 been emancipated from the restrictions imposed upon 
 Land-growing plants by fertilisation through the 
 medium of water. They exceed all other Vascular 
 plants both in number of species and of individuals, 
 
 ^^ • 
 
 Fig. 17. Zamia tJoridana. Mature free-swimming spermatozoid, or 
 male gamete. ( x 150.) (From Strasburger, after H. J. Webber.) 
 
 and form the dominating Flora of the present day. 
 On the other hand, the Cycads and Ginlgo show 
 all the signs of being archaic types. For the Cycads 
 are now represented by few genera, and are almost 
 confined to the Tropics, though formerly more Avidely 
 distributed ; while Ginlgo, which in earlier geological 
 periods was a relatively prevalent type, exists now 
 
80 PLANT-LIFE ON LAND [ch. v 
 
 only as G. hiloha, the Maiden-hair Tree of China and 
 Japan. Such facts give additional weight to the 
 conclusion which has been drawn. They show in the 
 form of practical results how essential that emanci- 
 pation was, in order that full advantage might be 
 taken of the opportunities offered by life upon 
 exposed land surfaces. 
 
CHAPTER VI 
 
 FIXITY OF POSITION AS A FACTOR IN THE 
 EVOLUTION OF PLANTS 
 
 Whenever there is heavy weather on our coast 
 combined with unusually high tides the surf disturbs 
 the sand collected in the rocky inlets, and as likely as 
 not lays bare the roots of land-plants which straggle 
 down to the high-water level. Here as elsewhere the 
 vegetation of the land encroaches upon the shore 
 with some degree of regularity of zonation, so that it 
 may almost reach downwards during the quieter 
 seasons to the usual high-tide mark. After such a 
 favourable period, if a heavy sea comes breaking in 
 at the full of a spring tide the encroachment is apt to 
 be checked, the foremost of the advanced guard are 
 uprooted, and the roots of those that pressed behind 
 are exposed. A glance at the wreckage demonstrates 
 at once the extent and the intimacy of the attach- 
 ment of the ordinary land-vegetation to the soil. 
 It impresses more forcibly than any contemplation of 
 
 B. 6 
 
82 PLANT-LIFE ON LAND [ch. 
 
 plants seen in the growing state the fixity of position 
 which is so prevalent a factor in plant-life. 
 
 It was long ago laid down as a general distinction 
 between animals and plants, that plants live, while 
 animals live and move. This antithesis still survives 
 in the mouth of the artist when he includes plants 
 under his designation of "still life." It is hardly 
 necessary to-day to refute this distinction, or to show 
 how far it is from accordance with fact. Every 
 elementary student knows that active life and move- 
 ment in some degree are inseparable. The movement 
 may be molecular only, or intracellular : in either case 
 it would be invisible to the naked eye, but still it 
 would be there. Moreover, the student soon learns 
 how closely such movements depend for their activity 
 upon those conditions which favour vigorous physio- 
 logical change : for him movement of some sort is 
 a common expression of life in plants as well as in 
 animals. Darwin's well-known book on the Power 
 of Movement in Plants has gone far to disillusion the 
 public on the point. He there showed that, apart 
 from the more rapid and obvious movements in such 
 cases as the sensitive plant {Mimosa), ordinary seed- 
 lings and growing plants at large execute movements. 
 These, being slow, are for the most part indistinguish- 
 able by the naked eye, but they may be readily 
 demonstrated by simple means. Thus we approach 
 the conclusion that even plants move in greater or 
 
VI] FIXITY OF POSITION IN PLANTS 8.3 
 
 less degree during active life, and that " still life," as 
 applied to them, is in point of fact a contradiction in 
 terms. 
 
 Nevertheless there is an underlying truth in the 
 old distinction between animals and plants, though it 
 applies only in a rough sense to the higher terms of 
 the two series. Fixity of position is the common lot 
 of the higher plants just as an ambulatory habit is 
 the rule for the higher animals. I propose, on the 
 one hand, to examine the circumstances which may 
 have led to the adoption of the fixed habit in plants, 
 and on the other to point out certain disabilities 
 which it imposes upon them. These have had to 
 be overcome before success could be assured among 
 the thronged life which subsists on the earth's 
 surface. 
 
 It is through the study of nutrition and mechanical 
 construction that the circumstances are to be sought 
 which have led to the adoption of the fixed habit by 
 plants. The two kingdoms differ widely in their 
 methods ; for while animals take their organic supply 
 at second hand, absorbing in some form or another 
 material already elaborated from its inorganic sources, 
 capturing it, and ingesting it often in bulk ; plants 
 go direct to those inorganic sources, and elaborate 
 their food themselves, absorbing its materials always 
 molecule by molecule. One consequence of this fun- 
 damental difference in the method of nutrition is that 
 
 6—2 
 
84 PLANT-LIFE ON LAND [ch. vi 
 
 in the plant the complete enclosure or encystment of 
 the primitively naked protoplast by a cell-wall pre- 
 sents no serious obstacle, provided that the cell- wall 
 be permeable to the molecules of the food to be taken 
 in, these being in the condition of solution in water. 
 But encystment brings great mechanical advantages, 
 and is indeed the chief means by which the construc- 
 tion of the large tissue-masses of the plant becomes 
 mechanically possible. So long as the wall is 
 sufficiently permeable, there is no need for any part 
 of the protoplast to be freely exposed, and as a 
 matter of fact, except among the simplest organisms, 
 or the reproductive cells of those which are more 
 complex, the cells of the plant-body are habitually 
 encysted (Fig. 18). But the cell- wall which is thus 
 a general feature in all but the simplest plants 
 presents at once an obstacle to free movement. The 
 protoplast is fettered by its armour more seriously 
 than any mediaeval knight. It has sold its birth- 
 right of free external movement for the pottage 
 of mechanical protection and structural stability. 
 Among the simpler aquatic organisms many naked 
 plant-forms are found, which like the simpler animals 
 are capable of active movement. But there are 
 others in which the movement is only an occasional 
 incident connected with propagation, others again in 
 which the encysted state is permanent. These may 
 be held to illustrate the sort of steps which have led 
 
Fig. 18. A, parenchymatous cell, highly magnified: at the exterior 
 is the cell-wall (shaded) which encysts the body : the latter is 
 composed of a protoplasmic lining which surrounds the large 
 watery vacuole, while in the centre the nucleus is suspended by 
 bridles of protoplasm. The arrows indicate the movements of 
 the protoplasm during life. 7) shows a portion of the cell-wall 
 and protoplasmic lining more highly magnified. (From Vines' 
 Lectures on Physiology of Plants, after Hanstein.) 
 
86 PLANT-LIFE ON LAND [ch. 
 
 from the primitive freedom of the protoplast to the 
 bondage of encystment. 
 
 The protoplast thus encysted remains isolated 
 only in the simplest forms. In all the more complex 
 the plant-body is made up of many, it may be of 
 millions of individual cells, derived ultimately by 
 division from a common source. Each is united with 
 its neighbours so as to constitute a tissue, or tissue- 
 system. The bondage of each encysted cell applies 
 collectively to the whole mass of them, and a large, 
 relatively immobile plant-body is the result. It is 
 no wonder that with tissues thus constituted the 
 movements of plants even in the young state are slow, 
 and act within narrow limits : and that as the tissues 
 become mature and their cell-walls thicken, the parts 
 composed of them become rigid, and lose the power 
 of movement altogether. 
 
 The nutrition of such encysted cells or cell-masses, 
 in the case of the Algae which inhabit fresh or salt 
 water, may take place at any point of their surface 
 which is exposed to the surrounding medium. Such 
 Algae are in simple cases suspended without attach- 
 ment, and constitute the large proportion of the so- 
 called "plankton," or floating life. They may be 
 collected in quantity from the surface of salt or fresh 
 water, in tow-nets of muslin drawn in the Avake of a 
 boat. The collection will be found to consist for the 
 most part of relatively simple organisms of small size. 
 
VI] FIXITY OF POSITION IN PLANTS 87 
 
 But some few plants of larger growth, such as the 
 Avell-known Gulf- Weed {Sargassum), may also float 
 unattached, growing and taking nourishment at the 
 surface of the open sea. This is, however, excep- 
 tional, and for the most part the more advanced 
 vegetation of salt and fresh water is attached to the 
 substratum, though the reason for this is not directly 
 one of nutrition, for they still feed by absorption at 
 the general exposed surface. The fact that in the 
 sea, in large bodies of fresh water, and in streams the 
 medium in which the plant lives is always changing 
 owing to the tides, currents, and general water-move- 
 ments, materially aids nutrition, for by this means 
 fresh supplies of inorganic materials are continually 
 being presented to the floating plants. 
 
 Coming finally to the vegetation of the land, we 
 find it composed essentially of plants rooted in the 
 ground. The extent and effectiveness of the attach- 
 ment are well seen when the roots are washed clear 
 of the soil, as on the shore about high-tide mark, or 
 along the banks of a stream that has been in spate. 
 The reasons for this fixity by the root are primarily 
 mechanical and nutritive. It is by such anchoring of 
 the plant firndy in the soil that it is possible for it to 
 raise its limbs and leaves upwards to expose them to 
 light and air. And, as every one knows, this is a 
 condition necessary for the successful nutrition of the 
 green plant. But, secondly, it is in the root-system 
 
88 PLANT-LIFE ON LAND [CH. 
 
 that the absorption of water and of the salts dissolved 
 in it is localised. These are abstracted from the soil 
 by the roots, to be carried by the transpiration stream 
 to the foliage, where the water evaporates away, 
 leaving the salts in the very region where the con- 
 struction of new organic stuffs is proceeding. More- 
 over the supply of food stuifs is further facilitated by 
 constant movement of water in the soil. This, together 
 with the growth and spreading of the roots, and the 
 recurrent renewal of their absorbing surfaces, result 
 in conditions which bring the plant in touch with ever 
 fresh supplies of raw materials. It is thus seen that 
 the fixed position of the plant in the soil is a necessary 
 condition of successful nutrition in all the ordinary 
 vegetation of the land. A measure of its effectiveness 
 may be seen in the permanence of large trees, such 
 as the Sequoias, or Mammoth Trees of California, 
 which bear evidence of individual growth for over 
 1000 years. 
 
 The facts alluded to in the preceding paragraphs 
 are so familiar that one is apt to neglect the important 
 restrictions which necessarily follow from them. In 
 considering these it will be well to compare the 
 higher plants, which are typically fixed to the sub- 
 stratum, with the higher animals which are ambulatory 
 in the habit. So we shall see actually worked out in 
 practice the consequences which this difference in 
 habit has entailed. The most important disabilities 
 
VI] FIXITY OF POSITION IN PLANTS 89 
 
 under which the stationary plant suffers as compared 
 with the freely mobile animal are four: (1) difficulties 
 of self-protection against animal attack, and (2) against 
 climatic conditions : (3) difficulties in effecting polli- 
 nation and intercrossing, and (4) in the distribution of 
 the new germs when produced. These will severally 
 be considered, and the methods will be explained by 
 which plants have met the problems raised by their 
 immobility. 
 
 The stationary plant is the natural victim of the 
 mobile herbivorous animal, and in many cases, such 
 as the ordinary pasture grasses, clover, oi* plantain, 
 there are no special means of defence. The cater- 
 pillar, the slug, and in tropical countries the leaf- 
 cutting ant all take their toll, as well as the larger 
 grazing animals, and frequently without any reprisals. 
 The only resource of the victim is to restore by 
 renewed growth as quickly as possible the parts that 
 have been lost. The animal, on the other hand, which 
 is the victim of a predatory attack has the chance of 
 escape by a combination of wariness and speed, but 
 this is denied to the fixed plant. Other means, 
 however, of protection of the plant against predatory 
 animals exist, and are effective. Some plants, such 
 as the Spurges and Asclepiads, contain distasteful 
 substances in their milky juice : others, such as the 
 Dock and Wood-Sorrel, and some Begonias are 
 protected by their acid taste : others such as the 
 
90 PLANT-LIFE ON LAND [CH. 
 
 Rue and the Sweet Rush (Acorus) by ethereal oils : 
 others again are protected by sharp needle-shaped 
 crystals embedded in their tissues. These, which are 
 especially effective against the attacks of snails, are 
 found in many Monocotyledons, such as Narcissus or 
 Orchis, and in some Dicotyledons, such as the Vine. 
 The sharp crystals are usually associated with mucil- 
 age, which swells on access of water when the tissues 
 are crushed or cut by chewing or biting. The crystals 
 are thus dislodged. Pointing irregularly in all direc- 
 tions, and puncturing the delicate tissues of the 
 mouth, they make the plant distasteful, and thus 
 protect it from further attack. The experiments of 
 Professor Stahl with snails have shown how effective 
 this protection actually is, even when the snails had 
 been famished for the purpose of the test. In other 
 cases the protection may be by pointed hairs, spines 
 or thorns, and this is particularly prevalent in dry 
 climates, where the succulent character of the vegeta- 
 tion would offer peculiar attractions to animals. The 
 most conspicuous examples are among the Cactaceae. 
 
 These notes must suffice to suggest some of the 
 many ways in which plants, owing to relatively minor 
 characters which they possess, are enabled to subsist 
 even where they are exposed to the attacks of 
 herbivorous animals. 
 
 Similarly they have to meet the risks of climate. 
 The mobile animal may protect itself against these 
 
VI] FIXITY OF POSITION IN PLANTS 91 
 
 risks ill various ways : such as by migration, or by 
 retiring into nests or burrows. The fixed plant has 
 to remain where it is. It may hibernate, however, 
 underground, as do many herbaceous and bulbous 
 plants ; or it may reduce its physiological risks by the 
 fall of the leaf, as do our ordinary deciduous trees in 
 the autumn ; or it may elude the period of extreme 
 conditions in the form of seeds or resting spores, 
 which are shown to be more resistant than the 
 actively vegetating plant. But it would take too 
 long to do more than merely suggest these as some 
 of the many devices by which plants overcome the 
 difficulties of climatic stress, to which their fixed 
 position condemns them. 
 
 A still more weighty disability than those which we 
 have thus seen to follow on the adoption of a fixed 
 position, is the difficulty in effecting pollination, and 
 its usual concomitant intercrossing. This is not the 
 place to discuss the advantage which follows on cross- 
 fertilisation in plants. It may be accepted as a general 
 principle that advantage does accrue. A general 
 reference may be given to Darwin's book on The 
 Effects of Cross and Self-fertilisation in the Vegetable 
 Kingdom. He there states, in his last chapter, that 
 "the first and most important of the conclusions 
 which may be drawn from the observations given 
 in this volume is that cross-fertilisation is generally 
 beneficial, and self-fertilisation injurious." In am- 
 
92 PLANT-LIFE ON LAND [ch. 
 
 bulatory organisms, such as the higher animals, the 
 search for a mate is readily carried out. But where 
 the organism is fixed, that fact at once places fertili- 
 sation and still more intercrossing at a disadvantage. 
 It is obvious that in them special means will have to 
 be provided in order to ensure its taking place. 
 When the importance of intercrossing is fully realised, 
 as well as the embargo on its ready occuri*ence which 
 follows from the fixity of position, it becomes in- 
 telligible that the sacrifices to secure it should be 
 great, and the means employed various and even 
 recondite. 
 
 Few subjects within the scope of botanical science 
 have raised more interest for the general reading 
 public than the cross-pollination of Flowering plants. 
 Ever since the time of Sprengel, who first demonstrated 
 the importance of animal agency for this end, and 
 drew attention to the specialisation of flowers as 
 mechanisms which should co-operate with the active 
 insect, the interest has been on the increase. But it 
 was specially stimulated in later years by the writings 
 of Darwin, and of Miiller, and has been expanded by 
 the observations of many other authors. It is now 
 a matter of common knowledge that not only are 
 insects, snails, birds and even bats made use of as 
 the carriers of pollen from flower to flower, but the 
 natural motor impulses of winds and moving water 
 are also employed. It has also been pointed out how 
 
VI] FIXITY OF POSITION IN PLANTS 93 
 
 mutually adaptable, and indeed mutually dependent, 
 certain plants and insects are upon one another. No 
 better example of this can be quoted than that of the 
 genus Aconitimi (Monkshood), and the humble-bees 
 that pollinate it. The northern limits of distribution 
 of the two in Asia coincide with an exactitude that 
 can only mean an intimate biological relation. This 
 is not the place to describe such observations in detail, 
 but rather to consider the conditions which have made 
 it necessary to resort to such artifices, and the evolu- 
 tionary steps which may have led to their adoption. 
 These conditions, simple though they may be, are 
 frequently overlooked by those who pursue this 
 branch of observation, or omitted from popular state- 
 ments on the subject. Their recognition, however, 
 must underly any rational study of pollination. 
 
 The Flowering plants of the land were without 
 doubt evolved from Fern-like plants, and these again 
 are generally held to have originated from the 
 primitive Algal Flora of the water. In such organ- 
 isms as these the male cells, and sometimes the 
 female also, are capable of independent movement 
 in water, into which they are extruded at maturity 
 (compare Fig. 2). And if they come, as they frequently 
 of necessity do, from different parent plants, the cross- 
 ing is easily effected as a consequence of their own 
 independent powers of movement. In the Pterido- 
 phytes such as the Ferns, we see organisms which, 
 
94 PLANT-LIFE ON LAND [CH. 
 
 originating from an Algal source, have adapted 
 themselves to life upon the land. But their sexual 
 propagation is still through the medium of external 
 fluid water, to which they have occasional access in 
 case of rain or copious dew (compare Figs. 8 and 9). 
 Their spermatozoids are capable of active transit 
 through water, and their course has been shown not 
 to be entirely at haphazard, but a chemically directive 
 influence is exerted by the diffusion of soluble 
 substance from the neighbourhood of the egg-cell, 
 which attracts the motile sperm. In such cases the 
 obstacles to intercrossing are not such as to require 
 extraneous aid, and there are analogies with what 
 occurs among ambulatory animals. 
 
 But it is otherwise with those organisms which 
 have taken the further step in specialisation to life 
 on the land involved in the adoption of the Seed- 
 habit. In these a condition for fertilisation to take 
 place is that by some means the pollen-grain shall be 
 transferred bodily from the stamen where it is pro- 
 duced to the stigma, or in Gymnosperms to the ovule, 
 or future seed itself. Since the stamen may be on a 
 dififerent branch, or even on a different plant from the 
 ovule, a real transfer, often through a considerable 
 space, is a necessary feature of propagation. The 
 pollen-grain is itself incapable of spontaneous move- 
 ment. And so some external agency must of necessity 
 be called in if pollination is to be carried out at all. 
 
VI] FIXITY OF POSITION IN PLANTS 95 
 
 The origin of Seed-plants having this requirement 
 dates back to the most ancient epoch which has left 
 to us any remains of terrestrial plants. The earliest 
 Seed-plants (Gymnosperms) were probably as de- 
 pendent for pollination upon external agencies as 
 are the Seed-plants of the present time. Moreover, 
 since in most of these the male and female flowers 
 were distinct from one another, the carrying out of 
 pollination was for them a condition of setting seed 
 at all, not merely a condition of securing the ad- 
 vantages which follow from intercrossing. The call 
 for external help was thus not merely a matter of 
 advantage, but of imperious necessity. 
 
 There is no clear evidence how the earliest Seed- 
 plants were pollinated. The fact that the pollen was 
 transferred is proved by its observation actually 
 within the orifice of the ovule, in sections of fossils 
 of Carboniferous age. The grains were relatively 
 large and smooth, so that though the agency of 
 transfer may have been the wind, there was no 
 definite specialisation to that end. Certainly the 
 wind is the usual means of conveyance of the pollen 
 in the Gymnosperms of the present day, though 
 among them are some Avhich rely upon insect agency ; 
 and it is quite possible that among their early corre- 
 latives the latter may have figured more largely than 
 has hitherto been believed. But whatever may have 
 been the case for the more primitive Seed-plants, it 
 
96 PLANT-LIFE ON LAND [CH. 
 
 seems clear that in the Higher Flowering plants, 
 animal agency was early available, and was soon 
 made use of. There is ample evidence of insect 
 life from the Secondary Rocks, and it was in that 
 period that the outburst of evolution of Flowering 
 plants took place. Though many of the simpler 
 types employ the agency of the wind or of water, 
 there is good reason to believe that the more com- 
 plex flower structures were evolved correlative to 
 and together with their insect visitors, a parallelism 
 as probable as it is interesting. There may doubtless 
 have been cases of transfer from the one agency to 
 the other, as for instance in the Rue (Thalictrum), 
 which has become wind-pollinated in a family 
 (Ranunculaceae) as a rule insect-pollinated ; and 
 the converse is also possible. It is not our object 
 here to define the actual degree of dependence for 
 pollination upon one or the other of these two 
 important agencies, but rather to indicate that, 
 whatever the detail, this principle rules in Seed- 
 plants : — that in very many cases to secure pollina- 
 tion at all, and in all cases to secure the advantages 
 of intercrossing, some agency outside the plant itself 
 is a necessity ; and that this necessity arises primarily 
 from the immobility imposed by the rooted habit. 
 
 The fixed position is then the prime factor leading 
 to all those wonderful adaptations of the fiower which 
 have pollination as their end. It may also be lield as 
 
VI] FIXITY OF POSITION IN PLANTS 97 
 
 a circumstance favouring, and so helping to explain, 
 the prevalence of that type in flowering plants where 
 stamens and cari)els are present in the same flower. 
 This juxtaposition makes self-pollination possible, 
 and in many cases probable. There are indeed some 
 flowers which do not open at all : in these self- 
 pollination is virtually a certainty. Such arrange- 
 ments may be held to be a provision against the 
 risk of pollination failing. A higher degree of 
 certainty of setting seed is thus achieved than 
 would be possible by dependence upon extraneous 
 agents. Thus taking a broad view of the matter it 
 would appear that it is ultimately the fixed position 
 which has made hermaphroditism more common 
 among the higher terms of the Vegetable Kingdom 
 than it is among the Higher Animals. 
 
 Following a similar line of thought we may enquire 
 what is the reason for those varied methods by 
 which plants secure the distribution of their seeds. 
 The high importance of that distribution must first 
 be grasped. In order that each germ may have the 
 best chance of growing to maturity, it must on 
 germination take up its position in the soil at such 
 a distance from its fellows as not to compete with 
 them for light or sustenance. In proportion as this 
 is achieved with success there will be provision not 
 only for the maintenance of the race, but also for its 
 spread into regions hitherto unoccupied, with increased 
 
 B. 7 
 
98 PLANT-LIFE ON LAND [ch. 
 
 chance of survival as a consequence. In the case of 
 the Higher Animals the necessary spread of the race 
 is secured by individual movement, and accordingly 
 they possess no special means for the distribution of 
 their germs. A nest of young birds or rabbits dis- 
 perses of its own initiative on approaching maturity. 
 But in the case of the Higher Plants fixity is a con- 
 dition of nourishment, and such distribution as is 
 necessary must be secured for the germ while young. 
 When once the germ is established as a rooted plant 
 the opportunity is gone for ever. It need then be no 
 surprise, however much the details may command our 
 admiration, that the adaptive arrangements in plants 
 for the distribution of their germs should be varied 
 and eflPective. As in pollination, so also in seed- 
 distribution the foi'ces of nature, wind and water, are 
 used : the former easily wafts away the light seeds of 
 small size, such as those of the Orchidaceae, or 
 Ericaceae, without special adaptive structure. But 
 whole families, such as the Compositae, the Ascle- 
 piadaceae, and the Willows, and especially many trees 
 such as the Sycamore and Elm, show definite mechan- 
 isms which secure distribution of seeds of larger 
 dimensions, by flocculent hairs, or winged expansions, 
 readily caught by the breeze. Water transit is 
 proverbially cheap, and still larger seeds may be 
 conveyed by floating away from the parent plant. 
 This is seen in the Coco-nut, and as an extreme 
 
VI] FIXITY OF POSITION IN PLANTS 99 
 
 example, the double Coco-nut of the Seychelles 
 {Lodoicea) may be cited, probably the largest single- 
 seeded fruit in the Vegetable Kingdom. Again, 
 in some cases animal agency is used, externally by 
 hooks and barbs on the surface of the seed or fruit, 
 which catch upon the coat of a passing animal: or 
 internally by pulpy developments, which attract the 
 animal as food, and the seeds swallowed with the 
 pulp are deposited with the excreta at a distance. Or 
 plants may develope mechanically effective means of 
 propulsion of their own. The common Broom and 
 the hairy Bitter Cress have explosive fruits, which 
 scatter the seeds far and wide. An extreme case is 
 that of the Euphorbiaceous Sand-Box tree (Hura 
 crejntans), the woody fruit of which explodes with a 
 report like a pistol shot, and scatters the relatively 
 large seeds to a considerable distance. Or the 
 principle employed may be that of the common 
 squirt, as in Echalllum, the Squirting Cucumber, 
 which extrudes its semifluid pulp, seeds and all, to a 
 distance of many feet, as it detaches itself from its 
 stalk when ripe. These are merely examples of the 
 varied artifices employed by plants for the distribu- 
 tion of tlieir germs. The raison d'etre of all of them 
 is idtimately to be found in the fixity of position, 
 Avhich the plant assumes at once on germination. 
 
 It is thus seen that, in the first place, the encyst- 
 ment of the protoplast within a firm cell-wall, and 
 
 7—2 
 
100 PLANT-LIFE ON LAND [ch. 
 
 secondly, the adoption of a fixed position by the 
 plants of the ordinary land-vegetation for purposes 
 of nutrition, have introduced certain disabilities into 
 the life of the plant, and that these have had far 
 reaching effect upon the course of further develop- 
 ment. The early encystment, while it prevented the 
 free movement of the whole body of those aquatic 
 organisms which adopted it, affected their general 
 biology in a comparatively minor degree. For it Avas 
 still open to them to extrude individual protoplasts, 
 for purposes of propagation, into the water in which 
 they lived. And many of the lower forms do so 
 habitually, thus securing by their motility both 
 spread of the germs and opportunity for fertilisation. 
 But with the spread of vegetation to the land, where 
 the medium of water no longer gives free opportunity 
 at all times for the movement of germs, the need for 
 other means of spread became urgent. The results 
 are seen in the multifarious methods of distribution 
 of spores and seeds. The adoption of the seed-habit 
 necessitated also some mechanical means of transfer 
 of the pollen. This, together with the advantages 
 derived from intercrossing, have led to the wonderful 
 and varied devices for securing pollination. The 
 prime cause of the difficulties was the encystment of 
 the protoplasm, and the consequent immobility of the 
 organism as a whole. Fixity of position has in fact 
 dominated the whole course of evolution of plants. 
 
VI] FIXITY OF POSITION IN PLANTS 101 
 
 The difficulties which beset polHiiation and dissemina- 
 tion have followed as secondary consequences. They 
 have been overcome by those adaptations which 
 command our interest and admiration. But too 
 often the interest in the adaptations themselves has 
 tended to obscure the prime cause which brought 
 them into existence. It has been the object of this 
 essay to place the cause and its consequences in their 
 proper relation one to another. 
 
CHAPTER VII 
 
 PLANT POPULATION 
 
 An idle hour on a summer's afternoon may be 
 pleasantly passed by any one who knows the Native 
 Flora, in trying to identify all the plants within 
 reach, as he sits, perchance, on some grassy slope. 
 The vegetation of cliffs facing the sea, the turf on a 
 mountain-side, the dense wiry growth of the golf-links, 
 or the ordinary sward of a meadow would serve, all 
 different as they are, to propound each its own 
 conundrum. And happy may the observer feel who 
 comes well out of an exhaustive study of all the 
 plants great or small, complex or relatively simple, 
 that grow within the radius of his arm's length. 
 Often they will be in some stage of development 
 which does not show distinctive characters, and this 
 will itself complicate the problem, and provide 
 tantalising uncertainties. But supposing the in- 
 ventory to have been made with some degree of 
 completeness, and all the various dwellers within the 
 
CH. VII] PLANT POPULATION 103 
 
 limited circle to have been duly recognised, any 
 active mind will ask, Why are these plants here ? 
 How did they get here? Why these instead of a 
 hundred others? You may perhaps be able, where 
 the ground is open and not under cultivation, to rule 
 out the direct hand of Man, so often a disturber of 
 the order of Nature. With some certainty it may 
 then be concluded that it is really Nature's own 
 achievement which has been observed and analysed. 
 How then does Nature bring it about that certain 
 species are present, and others absent from this 
 particular area of the earth's surface? 
 
 There are two main factors in this problem. It is 
 quite clear that as all living plants arise from their 
 like, in some way the germs of the plants recognised, 
 or of their ultimate parents, must have arrived within 
 the area observed. The first factor is then how this 
 area acquired the germs of the plants living there. 
 But further the growing plant developes from the 
 germ only when the conditions are favourable. From 
 the presence of any such growing plant it may then 
 be inferred that the conditions have been at least 
 tolerable. That they must necessarily be so is the 
 second factor in our problem. It is not proposed 
 here to consider the effect of external conditions 
 upon the growth and establishment of each germ as 
 an independent plant. That would involve some 
 review of the means of accommodation of plants to 
 
104 PLANT-LIFE ON LAND [ch. 
 
 their habitat : or perhaps rather the negative side of 
 the question might force itself more clearly upon the 
 mind, viz. the failure of germs to establish themselves 
 where the conditions are more severe than their 
 constitution will stand. This study would require to 
 be carried out with separate reference to each of the 
 species represented on the list observed, since the 
 reasons for the presence of each may have been 
 distinct and separate from those of others : indeed it 
 is probable that they were so. Such questions may 
 be allowed to stand aside for the present, and the 
 first factor will remain as the subject for discussion 
 here, viz. how the given area of ground acquired the 
 germs of the plants now established there. The ques- 
 tion divides itself naturally again into two branches, 
 first the origination of the germs, and secondly, the 
 means of transfer of the germs themselves, or those 
 of their ultimate parents, to the spot where they have 
 developed into the plants which we see. 
 
 It will be obvious to any one who recognises fully 
 the ordinary forces of Nature, and especially the 
 movements of air and of water, and their secondary 
 effects upon the surface of the soil, and upon the 
 organisms growing upon it, that chance will enter 
 largely into the determination whether any given 
 germ, when separated from its parent plant and 
 exposed to their action, shall lodge finally in one spot 
 or another. The limited area within reach as we sit 
 
VII] PLANT POPULATION 105 
 
 may be taken as a unit, and considered among the 
 millions of like areas which go to form a country-side. 
 What is the probability of the light grain of some 
 grass, say of Holcus, Fescue, or of the Trembling 
 Grass, with its chaffy paleae serving as sails, being 
 carried by the wind, and finally coming to rest, till 
 under favourable circumstances it shall germinate ? 
 Obviously the chances are very remote, but equally 
 clear is it that the larger the number of germs 
 produced the greater will be the probability. We 
 shall then enquire with interest into the fecundity of 
 plants, as estimated by the number of germs they 
 produce in a given time ; for plainly this is a factor 
 which will go far in determining the plant-population as 
 we see it established in any area open to the free play 
 of natural conditions. 
 
 The- third Chapter of Darwin's Origin of Species 
 dealt with the geometrical ratio of increase of living 
 things. Following Malthus he there pointed out that 
 " there is no exception to the rule that every organic 
 being naturally increases at so high a rate, that, if 
 not destroyed, the earth would soon be covered by 
 the progeny of a single pair." The effect of a 
 geometrical ratio of increase is apt to be under- 
 estimated ; but a simple example makes it clear. If 
 a plant produces 10 seeds each year, and each of 
 these germinates, the result in six successive years 
 will be 10, 100, 1000, 10,000, 100,000, 1,000,000. 
 
106 PLANT-LIFE ON LAND [ch. 
 
 Plainly as the years go on the result becomes rapidly 
 very large. Already Linnaeus had calculated that if 
 an annual plant produced only two seeds, and their 
 seedlings next year produced two, and so on, then in 
 twenty years there would be a million plants. This 
 is, however, a very slow rate of breeding, and it will 
 be well to enquire what are the rates of production 
 of germs seen in well-known plants. Taking first the 
 case of Seed-plants, the following table gives the 
 results of careful computation by Kerner of the 
 number of seeds produced in a single season by an 
 average specimen of each : 
 
 Henbane {Hyoscyamiis niger) 10,000. 
 
 Radish {Raphanns Ra^yhanistrum) 12,000. 
 
 Plantain {Plantago major) 14,000. 
 Shepherd's Purse {Capsella Bursa-iyastoris) 64,000. 
 
 Fleabane {Erigeroii Canadense) 120,000. 
 
 Tobacco {Nicotiana Tabaemn) 360,000. 
 
 Flixweed {Sisijmhrimn Sophia) 730,000. 
 
 Extreme cases of productivity were found by 
 Darwin among the Orchidaceae, and his estimates of 
 the numbers of seeds were as follows : 
 
 
 per capsule 
 
 per plant 
 
 Cephalanthera 
 
 6020 
 
 24,080. 
 
 Orchis maculata 
 
 6200 
 
 186,300. 
 
 Acroj^era 
 
 371,250 
 
 74,000,000. 
 
 Maxillaria 
 
 1,756,440. 
 
 
VII] PLANT POPULATION 107 
 
 The Ferns also afford striking examples of an 
 extreme power of productivity. I have estimated 
 the number of spores of the Common Shield-Fern 
 {Nephrodium filix-mas) produced by a well-grown 
 plant in a single season at approximately 50 to 100 
 millions. But this is by no means the limit for plants 
 of that affinity, as the subjoined table shows, in which 
 the numbers quoted are estimated not for the whole 
 plant, but for the single leaf : 
 
 A tliyrium filtx-foemina 1 6,000,000. 
 
 Polypodium aiireum 96,000,000. 
 
 Cyathea dealhata 200,000,000. 
 
 Danaea 150,000,000. 
 
 Ka nlfussia 1 73,000,000. 
 
 Marattia 2,800,000,000. 
 
 Angiopterls 4,000,000,000. 
 
 The productivity of Fungi is well known, and 
 any one who has blown the spores off a fully matured 
 culture of some common Mould, and seen the dense 
 cloud that spreads into the air, would be prepared 
 for high numbers on a rough estimate being made of 
 them. In the common olive-green Mould {Aspergillus 
 herhariorum), the number of conidia produced upon 
 a single conidiophore or head is at a moderate estimate 
 about 1500. These heads are formed in countless 
 luimbers in a few days upon a suitable nutritive 
 medium. If 1000 of them were borne upon a single 
 
108 PLANT-LIFE ON LAND [ch. 
 
 square inch of its surface we arrive at the output of 
 1^ millions of conidia as the result of a few days' 
 growth over that limited area. 
 
 As a last example, taken this time from the 
 Bacteria, it has been stated by Cohn that in a suitable 
 medium at a temperature of 35° C. a cell of Bacillus 
 subtilis will take about 20 minutes to divide into two. 
 If this process be repeated continuously, and the 
 resulting cells all retain their vitality, the product of 
 a single germ would in a period of nine hours (i.e. in 
 a single night) amount to over 134 millions ! 
 
 Kerner has illustrated the results which would 
 follow if such numerical increase as that we have 
 been contemplating were actually carried out un- 
 checked, in the case of certain Seed-Plants. He 
 points out that if a Henbane plant developed 10,000 
 seeds in one year, and 10,000 plants sprang from 
 those seeds next year, and themselves produced 
 10,000 seeds each, by the end of five years ten 
 thousand billions of Henbane plants would have 
 come into existence. As the entire area of the dry 
 land of the earth is approximately one hundred and 
 thirty-six billion square metres, and there is room for 
 about 73 Henbane plants on one square metre, if all 
 the seeds referred to ripened and germinated, the 
 whole of the dry land would at the end of five years 
 be occupied. Or, in the case of the Flixweed 
 (Sisymbrium Sophia), the normal multiplication from 
 
VII] PLANT POPULATION 109 
 
 a single parent would if unchecked cover an area 
 2000 times as great as the surface of the dry land in 
 the course of three years. A glance at the figures 
 quoted for Orchids, Ferns, Moulds, and Bacteria 
 shows that the Flixweed is by no means an extreme 
 case of fecundity. It is hardly possible to express in 
 words the consequences of successful establishment 
 of every germ which such plants might produce within 
 even a moderate period of time. 
 
 There is no need to astound or stupify the mind 
 by the statement of further figures such as those 
 above quoted. No brain can realise what is meant 
 by a million units, and speaking of billions conveys 
 no more than some general impression of vastness. 
 What is desired is to make it clear that the production 
 of potential germs is very great, and that even in cases 
 of relatively low productivity the number of germs 
 produced is far in excess of the actual requirement 
 to make up directly for losses by death. There is in 
 fact an immense overplus, which may be held as a 
 very efficient reserve to meet, with an ample margin 
 to spare, all the contingencies involved in the estab- 
 lishment of the germ, and its continued existence up 
 to the time of its propagative maturity. 
 
 But there is another circumstance to be considered 
 besides the mere number of the progeny. There is a 
 diversity in different types of plants in the time 
 required for the individual to reach the reproductive 
 
no PLANT-LIFE ON LAND [ch. 
 
 stage. Clearly the shorter that time, other things 
 being equal, the greater will be the propagative power 
 of the species. The annual plant germinates, de- 
 velopes, fructifies, and dies all in a single season. 
 Sometimes in arctic or alpine regions (which, however, 
 are on that account little suited to the life of annuals) 
 that season may be only a few weeks in duration. On 
 the other hand, many plants live and grow for a long 
 term of years merely as vegetative individuals, enter- 
 ing late upon a propagative period. In some cases, 
 as the gigantic Talipot Palm {Coryplia), or many Bam- 
 boos, the parent plant then dies. In other cases, as in 
 many forest trees, the fructification may be rej^eated 
 annually. In others again, as in the Common Beech, 
 a period of storage of nutriment may extend over a 
 series of years, to be terminated by a profuse fructi- 
 fication which suddenly depletes the store. Such 
 differences of behaviour modify, it is true, the details 
 of the propagative output, but the rate of increase is 
 as a rule so great that their effect is apt to be 
 swamped in the vastness of the totals, when taken 
 over an average of years. 
 
 In considering the chances of any given germ 
 becoming established as a new individual, the amount 
 of nutriment which it carries with it is a matter of 
 the highest moment. The larger the supply the more 
 thoroughly can the germ fit itself for acquiring its 
 own sustenance before the need for doing so actually 
 
VII] PLANT POPULATION 111 
 
 falls upon it. In the case of the spores of Mosses or 
 Ferns the store within the single-celled germ is small 
 indeed, but the grave risks which consequently attend 
 their germination are neutralised in great measure by 
 the enormous number of the chances of success. In 
 this lottery the proportion of prizes to blanks is small, 
 but the issue of tickets is very large. In the seed- 
 bearing plants the store that accompanies each germ 
 varies greatly, from that of the minute seeds of an 
 Orchis or Rhododendron with their exiguous store, 
 to the huge supply carried in the Coco-nut. In the 
 former cases the seeds are very numerous : in the 
 latter a solitary large seed is matured from each 
 flower. In the case of large seeds the issue of lottery 
 tickets is not great, but there is a reasonable pro- 
 bability of each bringing a prize. 
 
 Obviously the mere production of germs is not all 
 that is necessary. If those of the same plant remain 
 in close juxtaposition, in cases of the large output of 
 germs, the young plants on germination would be so 
 crowded that an internecine struggle would ensue 
 between them. To have a good chance of success 
 each must be separated from its neighbours : dis- 
 semination is essential, and it Avill be effected with 
 the greatest difficulty where the seeds are largest. 
 The agencies by which this is carried out have already 
 been alluded to above (p. 98), viz. spontaneous 
 ejection, transfer by wind, and water, and by animal 
 
112 PLANT-LIFE ON LAND [ch. 
 
 movement Putting on one side the spontaneous 
 impulse of mechanical ejection as effective only 
 within limited range, the most important agencies of 
 transport are by wind, by water, and by animals. As 
 a rule the consequences of their action are not very 
 obvious owing to the ground being already tenanted 
 by a mixed vegetation. It is only where a perfectly 
 sterile area has to be peopled with a new covering of 
 vegetation, or when a new organism gains access to 
 an area previously untenanted by it, that the results 
 can be fully appreciated. An experiment upon the 
 grand scale was made in the formation of a completely 
 new Flora of the Island of Krakatau, and fortunately 
 its results were followed by competent observers who 
 kept careful records. These form the best authentic 
 story of the natural formation of a plant-population 
 where none existed before. 
 
 Up to 1883 the islands forming the small group in 
 the Sunda Strait between Java and Sumatra, of Avhich 
 Krakatau is the largest, were covered by dense 
 vegetation. From May to August of that year suc- 
 cessive volcanic eruptions resulted in the complete 
 stei-ilisation of the surface, which was covered by hot 
 stones and ashes. Thus on cooling an miinhabited 
 desert was exposed, lying at a distance of fully 12 
 miles from the nearest living vegetation. In the 
 intervening 25 years a new Flora has sprung up upon 
 the islands. This has been studied at intervals : thQ 
 
VII] PLANT POPULATION 113 
 
 late Dr Treub, who visited Krakatau in 1886, con- 
 cluded that the first colonists were blue-green Algae 
 associated with Diatoms and Bacteria. These formed 
 a suitable nidus for the spores of Mosses and Ferns, 
 and for the seeds of some Flowering plants adapted 
 for dispersal by winds. On the beach were found the 
 fruits and seeds of Flowering plants some of which 
 had germinated ; many of them belonged to the 
 characteristic strand-flora of the Malay Region. But 
 plants introduced by animals or by man were not 
 found by him on this visit, which took place only 
 three years after the eruption. In 1897 Penzig 
 visited the island, and estimated that of the Flower- 
 ing plants noted 60*39 "/o had reached it by ocean 
 currents, 32*07 ^/o by wind agency, and only 7*54 7o had 
 been transported by fruit-eating animals and man. On 
 a subsequent visit by a party of botanists in 1906, the 
 results as stated by Ernst show that though these 
 proportions for Flowering plants were not exactly 
 maintained, still the largest number were borne by 
 water transit, and the smallest by animal agency. If 
 the Ferns be added to the list of plants with wind- 
 borne germs, this would raise the estimate of the 
 Vascular plants which had arrived in this way to 37 7o- 
 Thus for an oceanic island the most eftective agency 
 of transit is water : wind-carriage takes a middle 
 place, and transit by animal agency is the least 
 effective of the three. 
 
 B. 8 
 
114 PLANT-LIFE ON LAND [ch. 
 
 The results of successful dispersal combined with 
 high fecundity in any given organism come out clearly 
 in cases of invasion of areas j^reviously untenanted 
 by it. Darwin, in the Voyage of the Beagle, 
 quotes the case of the Cardoon Thistle in various 
 districts of South America. Its germs are spread by 
 the wind. Though not a native, it has by this means 
 occupied hundreds of square miles of country to the 
 exclusion of the native Flora. Similarly in Ceylon, 
 Lantaua, though introduced not long ago as an 
 ornamental garden plant, has spread throughout the 
 island, and forms dense thickets wherever the land 
 falls out of cultivation. The dispersing agents here 
 are birds, which greedily eat the pulpy fruits. But 
 we need not go so far afield as South America or 
 Ceylon for our examples. A very striking instance 
 of the ubiquity of germs, and the occupation by them 
 of any suitable nidus, is seen in the almost invariable 
 appearance of the Common Cord Moss (Fimaria 
 hygrometrica) on cinder paths, or places where the 
 ground has been burnt. There may apparently be 
 none of the Moss in the near neighbourhood : the 
 ground has been sterilised by heat. It can only be 
 that the spores are conveyed by currents of air, in 
 which countless numbers are present, but relatively 
 few find a spot for germination. The case is similar 
 for the appearance of Moulds on bread recently 
 baked, but kept in a confined atmosphere. Such 
 
VII] PLANT POPULATION 115 
 
 examples illustrate the magnitude, and the far reach- 
 ing character of the results which may follow, in 
 cases where the immense potentialities conferred upon 
 organisms by the geometrical ratio of increase are 
 combined with effective means of dispersal. Most 
 plants possess some such potentialities, but few find 
 the opportunity of realising them. 
 
 The failure in so many cases leads us to enquire 
 what becomes of the enormous surplus of potential 
 lives Avhich never get beyond the initial stage of the 
 germ ? The fact is that the risks of youth are very 
 great indeed. Many germs are killed off almost at 
 once by unfavourable conditions, such as undue 
 temperature, or drought. Light affects some injuri- 
 ously, and happily this is the case with many Bacteria. 
 INlany fail to find a suitable nidus for germination ; 
 others succumb to unsuitable seasonal changes in the 
 defenceless condition of the seedling. Competition 
 crowds out others. Many fall victims to the predatory 
 attacks of animals, which naturally divert to their 
 own uses any food-stores designed for the germ. 
 Fungal attack accounts for the failure of others, and 
 especially in the seedling state. When we contem- 
 plate the multiplicity and the insistence of these risks, 
 the cause for astonishment is rather that any come 
 through the ordeal than that so many fail. There is, 
 however, a more occult series of obstacles to success 
 than those which have been mentioned, and though 
 
 8—2 
 
116 PLANT-LIFE ON LAND [ch. 
 
 they are less obvious they are no less potent in 
 limiting- a plant-population. I mean the inter-rela- 
 tions of organisms. Relatively few plants complete 
 their whole life-cycle independently of other living 
 things, and the degree of inter-dependence is often 
 a surprise to beginners. Darwin in The Origin of 
 S^Mcies cited the example of Red Clover and Cats. 
 Having shown that the Clover is absolutely dependent 
 upon Humble-bees for its pollination, without which 
 no seed is set, he further pointed out that the number 
 of Humble-bees depends in great measure upon the 
 number of Field Mice in the district, which destroy 
 their combs and nests. The number of Mice is 
 dependent on the number of Cats, and he concludes 
 that " it is quite credible that the presence of a feline 
 animal in large numbers in a district might determine, 
 through the intervention first of mice and then of 
 bees, the frequency of certain flowers in that district." 
 Again, it has been shown by elaborate observations 
 in Europe and Asia that the northern limit of dis- 
 tribution of the Monkshood and that of the Humble- 
 bees which pollinate their flowers, is almost exactly 
 coincident, a fact which clearly points to an inter- 
 dependence. Many similar instances might be quoted. 
 But such relations are not confined to the higher 
 plants : Goebel quotes the case of the Splachnaceae, 
 those bright red and yellow Mosses which inhabit the 
 dung and remains of animals. The question is how 
 
VII] PLANT POPULATION 117 
 
 they attain with a high degree of certainty to this 
 peculiar and circumscribed nidus, especially as their 
 spores are aggregated in a sticky mass. It appears 
 that Flies are the agents, and passing from station to 
 station for the purpose of oviposition, they convey 
 the sticky spores from old cultures of the Moss to the 
 fresh dung. It is hard to see how this could possibly 
 be effected without insect agency. Another case is 
 that of the fungus, Plloholns, which grows on the 
 dung of horses and cows. When matui*e it can shoot 
 off its sporangium with its sticky mass of spores to a 
 considerable distance, and they adhere to grass or 
 herbage in the vicinity. If this again be eaten by 
 horses or cows, the spores passing through the 
 alimentary tract will be ready to germinate upon the 
 excreta, and so are very efficiently dispersed. These 
 are examples of that inter-dependence which is so 
 frequently a more or less necessary condition of the 
 successful completion of the life-story. Such relations 
 will go far to determine the numbers and spread of 
 the species involved. It may thus happen that where 
 the production of germs, their dissemination, and 
 gei-mination may have all been achieved, the species 
 may still fail by reason of its inability, in some other 
 respect, to complete the cycle of its life. 
 
 The general question which will present itself with 
 some insistence is, what positive advantages following 
 from the over-production of germs can repay the race 
 
118 PLANT-LIFE ON LAND [CH. 
 
 for the vast expenditure of material upon them ? A first 
 result is the provision with a high degree of probability 
 for the maintenance of the race in full numbers. The 
 fisherman knows that if he takes a trout in a certain 
 pool its place will be almost certainly occupied before 
 long by another. Naturally such replacement of 
 individuals cannot occur with any degree of regularity 
 among the rooted plants of our area of sward. But 
 the enormous over-production tends in this direction, 
 and Avill suffice to secure a reasonable average over 
 all. A second advantage gained is the probability of 
 spread of the species to any new spot which is 
 favourable, and the incursions of alien plants fully 
 show how effective this may be, as soon as opportunity 
 offers. A third result, and certainly not the least 
 important, is that the overplus gives a basis for 
 Natural Selection, bringing as a consequence the 
 maintenance of the stamina of the race by the 
 elimination of weaklings, and the preservation of 
 favourable variations, with the consequent possibility 
 of advance to a state of higher efficiency. 
 
 In late years there has been a definite tendency 
 to minimise the effect of Natural Selection. It is 
 hardly necessary to point out that Selection in itself 
 is not a factor of advance. Naturally it can only 
 contribute indirectly by the elimination of weaklings, 
 and by sifting out favourable variations from among 
 the vast number of potential lives. The ultimate 
 
VII] PLANT POPULATION 119 
 
 question is the origin of those variations. Variants 
 from the type are classified as (a) Mutations, and 
 (b) Fhictuating Variations, and it is commonly held by 
 those who are engaged with enquiry into such matters 
 that the Mutations bring considerable divergence 
 from the type and are transmitted to the oiFspring, 
 while Fluctuating Variations involve as a rule minor 
 divergence from the type and are not transmissible to 
 the offspring. More especially has it been insisted 
 upon that characters acquired during the individual 
 life of the parent are not transmitted to the offspring. 
 It has been shown, it is true, that certain considerable 
 variations which are held as spontaneous Mutations 
 are transmissible, and that certain minor variations 
 rightly held as fluctuating variations are not trans- 
 mitted. But what is not yet proved to the satisfaction 
 of all is that no acquired characters are in whole or 
 in part transmissible : nor is it clear that there is 
 necessarily a distinction between minor mutations 
 and fluctuating variations. The precise statement of 
 the distinction between these two categories, and the 
 assumption on the basis of a limited experience that 
 the one is inherited by the offspring and the other 
 not, has placed an obstacle in the way of understanding 
 how direct adaptation to environment can possibly 
 proceed. It is hard indeed to believe that all the 
 wonderful aitconunodations of organisms to their sur- 
 roundings are the product of blind chance. If there 
 
120 PLANT-LIFE ON LAND [CH. 
 
 were any directive influence determining the course 
 of inherited variation, and natural selection were 
 operative upon the variations thus produced, the 
 results which we see would be readily understood. 
 At present such directive influence, traceable to the 
 immediate accommodation of the organism to its 
 environment, is directly ruled out by certain inves- 
 tigators. But there are many who hold their opinion 
 in suspense on such questions. They look hopefully 
 in the direction of a theory involving some form or 
 other of the storing up of past experience, and its 
 perpetuation in the features of the race. By selection 
 among organisms with such memorised records the 
 facts of adaptation to the environment would become 
 intelligible. But of this the demonstration is not yet 
 come. 
 
 Returning now, in conclusion, to the limited area 
 of sward with its varied inhabitants from which we 
 started this discussion, we shall see in it the result of 
 a balance struck by Organic Nature. On the one 
 hand is the fact of constant over-production of germs : 
 on the other is the imminence of adverse fate 
 threatening each life we see, while the field on which 
 this tense battle of the individual is being fought is 
 strewn with countless failures. Efliciency is the ruling 
 condition of existence, and it is maintained by selection 
 among multitudinous variants. If those variants are 
 favourable, an ever-increasing efficiency is what such 
 
VII] PLANT POPULATION 121 
 
 surroundings will naturally produce. The very plants 
 we observe growing within our arms-length may even 
 now be stamping upon their race new characters, 
 Avhich will form features of the vegetation of the 
 future. 
 
CHAPTER VIII 
 
 SAND DUNES 
 
 It has already been remarked that the sandy 
 beach between tide-marks, being desert, is botanically 
 uninteresting. But above high-tide level the seaward 
 fringe of the Land Flora presents many features that 
 may well arrest the attention. Where precipitous 
 rocks face the sea there is little to remark beyond 
 the straggling of the usual plants of the neighbour- 
 hood on to the slopes and ledges of the cliffs, but with 
 a few plants added that are peculiar to the coast. 
 Here may be found the Samphire, mentioned by 
 Shakespeare as gathered on Dover cliiFs, where it 
 still growls and is collected for pickling. Or in 
 Scotland the Lovage, which has been used as a pot- 
 herb. The Wild Cabbage also, and the Carrot, Beet, 
 and Sea-Kale occur here and there. In fact the 
 Coastal Flora has given us the original stocks of 
 many of our most ancient garden vegetables, the 
 selection of them by our predecessors having doubt- 
 less been based upon the succulence of their foliage, 
 which is in relation to their growth upon saline soil. 
 

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124 PLANT-LIFE ON LAND [ch. 
 
 A peculiar vegetation, however, appears in parts 
 of the coast-line where a sandy beach leads up to 
 a more level land-surface, and solid rock is absent, 
 or at least discontinuous, or covered out of sight. 
 There in the inlets and bays, or along considerable 
 lengths of the shore, may extend those lands claimed 
 by the Golfer as the only true "Links," protected 
 seawards by rougher Sand-hills or " Dunes." Lastly, 
 between these and the tide-marks there is usually 
 a narrow, but more or less level expanse of dry sand, 
 which may bear its own limited but interesting Flora. 
 The substratum of the Links and Dunes is all com- 
 posed of sand, with here and there it may be projecting 
 bosses of the underlying skeleton of solid rock. The 
 sand of the Dunes is entangled with rough Marram 
 Grass. That of the Links is mostly covered by a 
 continuous but thin sod, matted with a dense growth 
 of smaller plants. 
 
 Sand-hills or Dunes may be formed by the action 
 of the wind alone. Examples are seen in various 
 localities, but they have been studied Avith special 
 care in the Libyan Desert, where the wind-formed 
 Dune takes a very definite crescentic shape styled 
 a "Barchan" (Fig. 19). The moulding of the wind- 
 formed Dune is commonly such that a gradual slope 
 of 5 — 10 degrees on the windward side leads up to 
 a ridge, from which the surface again falls Avith a 
 slope of about 30 degrees on the leeward face. But 
 
VIII] SAND DUNES 125 
 
 as this formation of ridges depends upon constancy 
 of direction of the wind, it is only occasionally 
 apparent on our oavu coasts, and the ridges themselves 
 are only of small dimensions ; for here the variable 
 
 ^^P^'"^**^ 
 
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 'J' ■ ' ' 
 
 Fig. 20. Showing a stone, and a bunch of dead grass as seen on the 
 beach after a high wind. Each has a long sti'eamer of sand 
 collected under its lee. In the close foreground are wind-ripples, 
 
 direction of the wind is liable soon to destroy such 
 constancy of form as a gale of some days may have 
 produced. 
 
 There has been some controversy as to the method 
 
126 PLANT-LIFE OX LAND [ch. 
 
 of the formation of these wind-created Dunes. The 
 prevalent vieAV is that the sand hurried along by the 
 gale is heaped up over that already present till a 
 slight ridge appears, which is then constantly increased 
 by more and more being carried over it from the 
 windward side. The steeper angle of the leeward 
 face is then due to gravity acting on the grains which 
 lose pace on the sheltered side. This accounts for 
 the steeper slope, which advances constantly but 
 slowly down the prevailing wind. The plain fact is, 
 however, that, — putting such wind-formed Dunes on 
 one side since they do not form a leading feature 
 here at home, — the existence of definitely shaped 
 Sand-Dunes on our shores and the genesis and 
 maintenance of Sandy Links are essentially due to 
 vegetable life. It may accordingly be a matter of 
 interest to consider carefully how they originate. 
 
 The sand itself consists of the comminuted frag- 
 ments of rock or of sea shells, and is cast up by the 
 waves upon the beach. Thence it is liable to be carried 
 by wind upward to the land. Once deposited in any 
 given position each grain, being unattached, is free 
 to be moved on again to another spot by any gust of 
 wind. But the probability of this happening in the 
 case of any individual grain is less if it should have 
 lodged in some place protected from the wind, while 
 it is more likely that the wind-borne particles will in 
 the first instance settle wherever there is a relatively 
 
SAND DUNES 
 
 •%j^- ^ 
 
 Fig. 21. Plants of Salt- Wort {Sahola), after exposure to strong wind 
 blowing along the beach. Each plant has gathered around it a 
 hillock of sand. 
 
128 PLANT-LIFE ON LAND [ch. 
 
 quiet spot. Such quiet spots are found under the 
 lee of any obstacle, such as a stone, a seaweed, or 
 a living plant. Any one who observes the beach after 
 a high wind, especially if it blew in a direction follow- 
 ing the coast-line, will find innumerable instances 
 of the sand-streamers which thus collect under the 
 lee of any solid object, living or dead (Fig. 20). But 
 if the object itself be a living organism, and grows 
 upwards as the sand collects around it, then there is 
 the possibility of an actual building up of a permanent 
 heap, provided that the winds recur at intervals. 
 This is the principle which underlies the origin of 
 all permanent sand-formations on the coast, and the 
 conditions are sometimes repeated inland. It is 
 the presence of certain sand-dwelling plants which 
 provides in the first instance the sheltered spots for 
 the settling of the sand, and secondly, it is by their 
 continued growth that that degree of permanence 
 and enlargement is secured which is characteristic of 
 the Dunes and Links as compared with mere shifting 
 sands. 
 
 We may take the formations thus built up from 
 the sand in the order in which they severally present 
 themselves as we pass upwards from the high-tide 
 mark. First, there may be a zone of loose sand, dry 
 at the surface and easily shifted by the wind. 
 Spreading downwards into it, and not much, if at 
 all, raised above the beach, comes the advanced 
 
villi SAXD DUXES 129 
 
 guard ill the form of plants belonging to various 
 affinities, but having this in common that they are 
 of low stature, and of more or less creeping habit. 
 They are characteristically " Halophytes," that is 
 denizens of saline soil, and most of them bear the 
 mark of it in their fleshy habit, their smooth hairless 
 surfaces, and their bluish tint due to a thin protective 
 covering of wax. Among such may be seen at the 
 lowest levels the Orache (Atrijylex), and Seablite 
 (Suaeda), the Sea-Rocket (Cakile), the Salt- Wort 
 (Salsola) (Fig. 21), and Sea Purslane (Arenaria pep- 
 loides) : w ith these, or often forming dense patches by 
 themselves, are found the Sea-Couch Grass (Triticum 
 jimceum), and the Common Sand Sedge (Ccirex 
 arenaria). These plants are joined not uncommonly 
 by some ordinary land-plants, such as the Silver Weed 
 (Potentilla anserina), and various forms of the Couch 
 Grass (Triticum i^epens). An interesting though rare 
 plant that shares this habitat is the pink-flowering 
 Convolvulus ((7. soldanella) : it creeps along the sand 
 much in the same way as its relative, Ipomaea 2MS- 
 caj?rae, which is a notable sand-binder of tropical 
 shores. Such plants as these, or various representa- 
 tives and combinations of them, by their mode of 
 growth give a coherence to the otherwise loose sand, 
 binding it together by their roots and runners. At the 
 same time, when wind is drifting the loose grains 
 along the shore, the shoots and foliage of the growing 
 R. 9 
 
130 PLANT-LIFE 0:N^ LA^N^D [ch. viii 
 
 plants provide those local shelters in which the 
 moving sand collects. But as many of these plants 
 are annuals, while none grow to any considerable 
 height, they are not efficient in securing permanence, 
 or in promoting any considerable rise of level of 
 sand collected. The result is that the areas they 
 cover are usually flat, and slope directly down to the 
 general level of the beach. Their effect is thus apt 
 to be local, and insignificant when compared with 
 that of the more efficient sand-binders of the Dunes. 
 Nevertheless the methods of action of these plants 
 are well worthy of observation and study, both from 
 the point of view of the self-preservation of the 
 plants under their peculiar surroundings, and as 
 regards the practical binding effect which they 
 produce. 
 
 Next in order landward come the Dunes, which 
 rise more boldly from the level of the beach, but as 
 often as not they abut directly upon the high water- 
 mark, and the lower growths just described may be 
 entirely absent (Fig. 22). The Dunes that face the 
 sea are usually " White Dunes " : that is, the sand is 
 not covered in by vegetation, but is largely exposed, 
 so that the colour of the whole is that of the sand 
 itself rather than of the plants growing upon it. 
 They commonly present a steep face to the shore, 
 sloping more gently on the landward side. This is 
 probably due to their growth seawards being re- 
 
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132 PLANT-LIFE OX LAND [CH. 
 
 peatedly checked by the high tides and heavy winter 
 seas washing away their bases. The sand then falls 
 in steep avalanches from above, and may be heaped 
 up in various ways by the prevailing winds. But it 
 is hardly possible to give more than a very general 
 description of their form ; it is so various. The 
 factors that determine it are primarily the growth 
 of the plants which serve to collect the sand and to 
 bind it together ; and secondarily, the effect of the 
 wind in again undoing what the plants have done, 
 by carving out and redistributing the sand collected 
 under their influence ; for there is in the White 
 Dune formation a constant construction and as con- 
 stant a destruction going on so long as the surface 
 is not covered in by plant-growth. This absence of 
 permanence suggested the designation of "Shifting 
 Dunes." 
 
 Before we consider the plants which take a 
 leading hand in the formation and the shaping of 
 Dunes, it may be well to enquire what are the 
 qualifications for their success. In the first place. 
 Dune-forming plants must be perennials, xinnual 
 Dunes are always small and temporary, for when the 
 plants die at the end of the season the sand collected 
 round them is dispersed : this is the case with such 
 plants as Salsola (Fig. 21). Secondly, the plants 
 should be capable of spreading by means of runners, 
 or by adventitious buds upon their roots. By this 
 
VIIl] 
 
 SAND DUNES 
 
 133 
 
 means the area of the Dune will be extended, and 
 its growth to a greater height will be possible. A 
 
 1 ti||^^»^i.%J li 
 
 Fig. 23. A dense mat of Marram Grass from which the sand has 
 been washed away by the waves at high water, so as to show the 
 horizontal rhizomes and the roots in their natural positions as 
 they were embedded in the sand. 
 
 third point, which will give a peculiar advantage in 
 Dune-formation, is the capacity of the plant for 
 
134 PLANT-LIFE ON LAND [CH. 
 
 growing upwards to the light when it may have been 
 completely covered by blown sand. The more rapidly 
 and effectively this can be accomplished the greater 
 will be growth of the Dune. Lastly, owing to the 
 low specific heat of the sand, and its free exposure, 
 and the consequent rapid cooling at night and liability 
 to sudden heat during the day, it will be necessary 
 that the plants of the Dune-flora shall be xerophyti- 
 cally adapted, that is, that they shall be able to stand 
 sudden conditions of extreme heat and drought. It 
 will be apparent that relatively few plants are in a 
 position to meet all these requirements, and it need 
 therefore be no matter for surprise that the Dune- 
 forming Flora is a restricted one. 
 
 By far the most common and efifective Dune- 
 forming plant is the Marram Grass, or " Bent " as it 
 is called by golfers {Ammo})Mla arundinacea). It 
 will therefore be worth while to examine the Bent 
 Grass carefully. It appears coarsely and densely 
 tufted above ground, with long leaves sheathing 
 below, but narrow in form, and very gracefully curved 
 in their upper region. They are furnished with 
 sharply pricking points, and doubtless these aid the 
 young growing leaves in making their way upward 
 through the sand. Examining the leaf it is seen to 
 have a convex surface (the lower or abaxial), which 
 is hard and smooth, and a concave surface (the upper 
 or adaxial), which is marked by deep longitudinal 
 
VIII] SAND DUNES 135 
 
 furrows. The behaviour of these leaves under vary- 
 ing circumstances of wind and moisture is interesting. 
 It may be noted on any breezy day that the leaves 
 present their smooth and convex surface to the wind, 
 so that not only is their mechanical resistance to it 
 the most eifective, but also any sand it may convey 
 glances off instead of catching in the grooves of the 
 concave face. Another point which is certainly an 
 adaptive one is the capacity of the leaf for rolling 
 in its margins in dry weather till it looks like a length 
 of green wire. But when moisture is plentiful it 
 flattens out so that the smooth lower surface is almost 
 flat, and the grooved upper face is widely exposed. 
 This automatic change of form, which quickly alters 
 the general appearance of the grass after a shower, 
 is brought about by the contraction or expansion of 
 certain water-containing cells on the upper surface. 
 As these swell with moisture the leaf flattens, and 
 evaporation of water-vapour from the upper surface 
 is easy. As the moisture becomes deficient the leaves 
 contract, the margins of the blade are drawn together, 
 and evaporation is checked. Such automatic control 
 is one of those features which make life possible for 
 the plant under the exacting conditions of the sandy 
 Dune. The inflorescence appears as a dense white 
 panicle in July, but it presents no characters of 
 special interest. This much may be observed without 
 digging j^tlie plant up. But below the surface of the 
 
136 PLANT-LIFE OX LAND [ch. 
 
 sand are features of still greater moment as bearing 
 upon its value as a sand-binder. 
 
 Hidden in the sand are the long horizontally 
 running rhizomes of the Marram Grass that are 
 densely matted together, and are thus so marked a 
 factor in its success (Fig. 23). On them the leaves 
 are borne alternately at long intervals, and develope 
 only their lower sheathing part while the lamina 
 remains small. These rhizomes are found to be firm 
 and resistant like strong cord, and their mechanical 
 strength is again an important point. They may be 
 traced for long distances, and are found throughout 
 the structure of the Dunes, even to their base. At 
 each node where a leaf is inserted a number of roots 
 may arise, radiating outwards into the sand, while 
 in an axillary position a bud originates, the mode 
 of development of which may vary according to 
 circumstances (Fig. 24). It may grow horizontally 
 with long internodes, and become a new runner, 
 having its terminal bud sharpened and indurated 
 like the point of an awl : or it may turn upwards 
 and form a leafy shoot, which on emerging at the 
 surface of the sand will, by shortening its internodes 
 and developing its axillary buds, form one of those 
 dense leafy tufts so characteristic of the species. 
 It is the adaptability of this grass to its circumstances 
 in respect of direction of growth of its shoots, and 
 the degree of elongation of its internodes, combined 
 
VIII] SAND DUNES 1.37 
 
 with its xerophytic specialisation, that makes it before 
 all other plants the leading builder of Dunes. Other 
 grasses ;take part also, for instance the>Lyme-Grass 
 
 Fig. 24. Horizontal rhizome of Marram Grass, showing three nodes, 
 from which roots arise. From two of them leafy buds have grown 
 upwards through the sand. The arrow points towards the apex 
 of the rhizome. 
 
138 PLANT-LIFE ON LAND [ch. 
 
 {Elymus arenarius), which shares many of the 
 characters of the Marram, and the Sea- Couch Grass 
 (Trlticum junceum). But these are neither of them 
 so successful, the latter together with the Sand-Sedge 
 {Gar ex areiiaria) being deficient in capacity for 
 upward growth after being buried in the driven sand, 
 in which respect the Marram especially excels. 
 
 The White Dune thus formed is sometimes styled 
 the Shifting Dune. Having its sand retained only 
 by entanglement amongst the relatively lax growths 
 of the Marram, its surface is liable to be blown away 
 again, while the sand removed from the windward 
 side will be caught by the vegetation on the sheltered 
 side. More especially does this occur where the Dunes 
 have attained great height, for there not only are 
 they more exposed to the wind, but also the plants, 
 being higher above the level of the ground- water, are 
 apt to grow less strongly, and form a less efficient 
 protection. And so the whole Dune may appear to 
 change its position, advancing by degrees down the 
 prevailing wind. There is probably no better example 
 of this in Great Britain than that of the sands of 
 Culbin near Forres, on the south coast of the Moray 
 Firth. Moreover the history of that strange waste of 
 sand is so far known that an additional interest springs 
 from it. The estate of Culbin, extending to some 
 3600 acres, was in the l/th century celebrated for 
 its fertility. It^was intersected by the river Findhorn, 
 
yiii] SAND DUNES 139 
 
 and included, besides smaller holdings, some sixteen 
 farms. The disaster which buried the whole estate 
 beneath the sands came suddenly in the autumn of 
 1694. The sea had been encroaching extensively on 
 the land further to the westward, so that a large 
 expanse of sand was exposed at low water. It is 
 stated that a westerly gale carried immense quantities 
 of this sand over the fertile land, covering fields and 
 houses, burying the mansion-house itself, and even 
 diverting the course of the Findhorn river. Ever 
 since the Culbin Sands have been a vast shifting area. 
 If Marram Grass obtains a hold here or there, and 
 Dune-formation proceeds, it is again torn out by the 
 winds. A large part of the area remains as bare 
 Sand-hill, without a trace of vegetation upon it. 
 Here the surface sand is free to move with every 
 wind, and the form is constantly changing. The 
 effect of this is well shown at a point where a wood 
 of Scotch Firs had grown to maturity. The sand 
 advancing in a wreath some 40 feet high is gradually 
 enveloping the trees (Fig. 25). Elsewhere the sandy 
 pall is being removed again, and the dead stumps are 
 all that remains to show the destruction that has 
 been wrought (Fig. 26). The complete obliteration 
 of woods may be seen on even a larger scale else- 
 Avhere : for instance,:on the shores of Lake Michigan. 
 Such effects illustrate to the full the irresistible 
 advance of sand borne as individual grains by a wind 
 
140 PLANT-LIFE ON LAND [CH. viii 
 
 constant in direction, but not necessarily great in 
 power. The principle is the same as that which may 
 be followed on any Dune of small size, where the 
 wind has got the better of the binding vegetation. 
 
 Enough has been said to show the instability of 
 the White or Shifting Dune. But provided that the 
 conditions be quiescent, various plant-growths appear 
 between the tufts of Marram or other prime formers 
 of the Dune. These gradually cover the surface, 
 converting the formation to what is called Grey or 
 Stationary Dune. This constitutes a third zone on 
 the landward side of the chain of White Dunes. 
 The plants that bring this about are usually of low 
 growth and straggling habit. Small annuals or 
 biennials are found among them, such as Whitlow 
 Grass, Teesdalia, and species of ]Mouse-ear : small 
 Leguminous plants, such as Lotus, and species of 
 Clover and Vetch. The Ladies Bedstraw, various 
 small grasses, such as Air a, Agrostls, and Sheep's 
 Fescue : or where in the hollows water will sometimes 
 stand, species of Rush and Cotton Grass and Sedge 
 may appear. Mosses may take their place in this 
 attractive little Flora, some Fungi such as Puff-Balls 
 and Clavarias, and Lichens such as Cladonia. But 
 amongst the most effective plants which give a greater 
 degree of consistence to the Grey Dunes are certain 
 woody plants, such as the Creeping Willow {Salix 
 rej^eus), with its almost prostrate twigs, while the 
 
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142 PLANT-LIFE OX LAXD [ch. viii 
 
 little Burnet Rose {Rosa spinosissima) or the Rest 
 Harrow (Onotils spinosa) may add a charm as well 
 as a permanence to the formation. Of the larger 
 woody growths which often follow the formation of 
 permanent Dune, one of the most effective plants is 
 the Sea Buckthorn (Hippophae rliamnoides), which 
 is native in the south and is naturalised in Scotland. 
 Not only is it xerophytic in its character, but it also 
 fulfils the condition of spreading by the formation 
 of adventitious buds on its long creeping roots. 
 Lastly, such xerophytes as Gorse and the Heaths 
 and Ling, make their appearance as well, and when 
 once the Grey Dune is thus permanently established 
 many other plants follow, and constitute a Flora of 
 ever-increasing variety. 
 
 And so what is at first an unstable formation 
 becomes compacted till it acquires a settled character. 
 It must not, however, be thought that actual encroach- 
 ment upon the sea itself is a common occurrence. 
 Doubtless plant-growths, upon which Dune-formation 
 depends, are continually edging seawards ; but they 
 are liable to be as continually checked and curtailed 
 by the action of the waves at high water in stormy 
 weather. The methods of Dune-formation are not 
 aggressive : they are rather those of defence, prevent- 
 ing inroads. Consequently Dunes are most commonly 
 found to run in concave curves between headlands, 
 and to round ofi* the indentations of the coast-line, 
 
144 PLANT-LIFE OX LAND [ch. viii 
 
 rather than themselves to project seawards. Like 
 the softer tissues of the animal body which round 
 off the more abrupt outlines of the skeleton, so the 
 Dune-formation softens the harsher configuration of 
 the rocky framework of the coast. 
 
 Nevertheless on certain low-lying coasts, w^hich 
 have no resistant skeleton of firmer rocks, and thus 
 are liable to inroads of the sea, the defensive methods 
 of the Dune-formers may be of the highest importance. 
 Where a shallow, gently graded beach leads up to 
 high-w^ater mark, breaking thus the force of the 
 weaves even in stormy weather, the Dune-formation 
 may oppose an effective barrier to further advance. 
 Moreover, in such places the ample supply of sand that 
 may readily be blown from the beach makes Dune- 
 building easy. It is on certain stretches of the 
 Continental Coast bordering on the North Sea that 
 the Marram Grass and Lyme Grass attain their greatest 
 use. They are planted out according to strict method, 
 and are even protected by law^. Thus Dune-formation 
 may be not merely a picturesque incident of the 
 Coast, but it may also be of positive use to man. 
 In the next Chapter it will be shown that it may also 
 minister to his amusements. 
 
CHAPTER IX 
 
 GOLF LINKS 
 
 The game of golf finds its home at the sea-side. 
 Widespread as it is to day inland, it was essentially 
 of coastal origin. It was primarily a game to be 
 played on a sandy substratum, and the constant 
 effort of the inland green-keeper is to construct 
 features which are characteristic rather of the sea- 
 shore than of the midlands. However well he may 
 carry this out, and even where a sandy soil favours 
 his efforts, the inland course is a thing different 
 from the true coastal links. Perhaps it is in part 
 the tang of the sea, but assuredly it is in the 
 main the contour of the surface and the quality of 
 the turf, and of the sand below it, that make one 
 realise that golf at the coast is the reality, and 
 inland golf its mere shadow. Accordingly though 
 this Chapter relates nominally to golf-links in general, 
 it will apply particularly to coastal links as having 
 those characters which stamped the game in its 
 original form. 
 
 B. 10 
 
146 PLANT-LIFE ON LAND [ch. 
 
 The links of the sea coast ma}^ be as various in 
 conformation as the coast itself. In point of fact 
 the rock-sculpture which underlies the surface gives 
 them their primary characters. However thickly 
 covered by sand and soil and varied vegetation, 
 sooner or later the solid rock would be reached 
 by boring, and it is in the inlets of the coast-line, 
 and the depressions of this rock-surface, that the 
 materials collect to form the links themselves. These 
 may take the form either of towering Dunes, built 
 up by agencies explained in the preceding chapter, 
 or of more level sand-fields originating in various 
 ways, but still owing their outlines primaril}^ to 
 the underlying rocks. Though often out of sight 
 the rocky skeleton has thus been the prime factor 
 in the shaping of the links, and the broader features 
 of the course may for the most part be properly 
 traced back to it. 
 
 Apart from the general conformation of the links 
 thus defined by their rocky skeleton, the detailed 
 characters, whether of contour or of surface, arise 
 from the agencies which afiect the transfer and 
 lodgement of wind-borne sand. The mere existence 
 of an inlet or hollow in the framework would tend 
 to detain some of the sand blown upwards from the 
 beach. But much more effective is the influence of 
 perennial vegetation. Wherever this has obtained 
 a footing sand-aggregates collect, and grow with its 
 
IX 
 
 GOLF LINKS 147 
 
 growth. The most potent of all such influences has 
 doubtless been that of the INLarram or Bent Grass, 
 as explained in the foregoing Chapter. Let us hope 
 that its work is properly appreciated by golfers. 
 When a sliced drive lands a ball in the rough 
 skirting the sea, instead of giving vent to objurgations 
 on the Bents, it is well to remember that they are 
 after all the best friends of the golfer, for without 
 them the links, if they existed at all, would have 
 been relatively flat and featureless. The rounded 
 contours of the green, and especially those heights 
 which have earned for themselves such picturesque 
 local titles, and have caused so many moments of 
 exultation or of black despair, owe their origin alike 
 to this most effective of Dune-Formers. 
 
 But Ave have already seen that the AVhite Dune 
 which they at first produce is unstable, and liable 
 to shift, partly oAving to the isolation of the particles 
 of the sand loosely held betAveen the tufted leaves, 
 partly to the failure of the ^larram Grass itself as 
 the Dune grows higher. It requires the growth of 
 many smaller plants of various affinity, forming 
 combinations as various as the coasts on which they 
 dwell, to build up between the tufts of jMarram Grass 
 that dense felt Avhich first gives permanence to the 
 Dune. A sod is thus gradually compacted, which 
 covers over the loose sand and protects it, con- 
 verting the White or Shifting Dune into the Grey 
 
 10—2 
 
148 PLANT-LIFE ON LAND [ch. ix 
 
 or Permanent Dime. Every Golfer knows how 
 important is the continuity of this skin of turf, thin 
 and delicate as it is. If even a small hole in it be 
 left to itself it may be enlarged into an undesirable 
 bunker by the action of the wind whisking away 
 the loose sand that lies below. It is not without 
 good reason that the replacement of a " divot " cut 
 out by an iron club has become something more 
 than a courtesy of the links. It should be accepted 
 as an imperative rule, the observance of which is 
 merely continuing the order of Nature. But the 
 green-keeper, with his barrow of soil and packet 
 of grass-seed, is doubtless a more efficient agent in 
 the maintenance of the protective skin of fine turf : 
 for the replaced sod frequently fails to settle again, 
 especially where the turf is thin and sandy. 
 
 There are thus three factors which share the 
 prime construction of the sea-side Links. The first 
 is the rocky skeleton which defines the broad features 
 of outline. Secondly, there are the Dune-Builders, 
 by whose means the moving sand is temporarily 
 held, and aggregated into heaps of various form : 
 and thus are initiated those swelling contours which 
 give so much of their character to the coastal 
 courses. Thirdly, the skin of mixed vegetation 
 which follows, giving permanence to the otherwise 
 inconstant Dune. Jointly these factors supply that 
 raw material from which the fully protected course 
 
 
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150 pla:n^t-life on land [ch. 
 
 may be produced (Fig. 27). The further agents are 
 Animals and Man. Of Animals the most effective 
 to this end are rabbits and sheep. The former do 
 harm as well as good. It is true they nibble down 
 the coarser growths, keeping in check the exuberance 
 of certain of the woody plants that invade the links, 
 and do so much to give them permanence. They 
 crop the sward to an even velvet, stiff it is true 
 in the pile, but short and smooth such as the 
 Golfer loves, and seldom finds except on the true 
 Links of the coast. So close is this film of turf to 
 the underlying sand that as the ball falls upon it 
 from a long tee shot the sound is sometimes like 
 the ringing of a bell : veritably it is the sound of 
 the "Musical Sands." But while rabbits thus help 
 to produce a suitable turf, their holes and scrapings 
 are a perpetual trouble, and discount in appreciable 
 degree the advantages which they bring. Over and 
 above the irritation from loss of balls, and " cupped " 
 lies, there is the risk from opening up the underlying 
 sand to the action of the wind. The close nibbling 
 of sheep is also effective without these disabilities, 
 but they do not crop so close as rabbits. Both 
 agents frequently work together, but the rabbit is 
 there on sufferance rather than by choice, while 
 the sheep is penned upon the Links on purpose. 
 
 The Raw ^Material of the Golf Course, originating 
 as the resultant of the factors named above, and 
 
IX] GOLF LINKS 151 
 
 trimmed by animal agency, presents many interesting 
 features for analysis. The varying characters seen 
 on divers shores may thus be traced back to tlieir 
 origin through various conflicting influences. Here 
 the rocky substratum rises to the surface in pro- 
 jecting bosses, there it is more flat in form, and the 
 wind-borne sand covers it entirely out of view. 
 Close by an eflete Dune with its grasses weakened in 
 growth is being attacked by the wind, and eroded into 
 hollows or "Blow-outs," which are however checked in 
 their spread by the covering of firmer skin compacted 
 of finer grasses, bedstraw, and thyme. Here may be 
 a strong stifi" growth of whins, constantly edging 
 forwards and as constantly trimmed back at the 
 margin by persistent nibbling of animals. Other 
 spots may be roughened by heather, or the creeping 
 willow, or made scrubby by growths of elder or 
 other shrubs. Lastly, where an old " blow-out " has 
 occurred, eroding the sand almost down to the moist 
 water-table itself, the sour and muddy soil Avill 
 harbour a host of rushes and sedges, stiff* and thick 
 in growth, and standing after rain ankle-deep in 
 "casual water." 
 
 Such is the material upon which the green-keeper 
 has to exercise his skill, whether constructive or 
 destructive. It is an ordered balance of Nature, 
 irregular enough in its results it is true, upon which 
 he enters as a disturbing influence. With his scythe, 
 
152 PLANT-LIFE ON LAND [ch. 
 
 his mowing machine, and his roller he does in 
 mechanical and prosaic fashion what is so much 
 more picturesquely done by the free agencies of 
 Nature. He fixes the " blow-outs " as bunkers, often 
 arresting the effect of the wind by lines of railway 
 sleepers, or piles of sods, thus straightening their 
 irregular edges into rigid lines. He opens out new 
 and artificial hazards, placed not by accident as 
 were those of the original course, but as intentional 
 traps which bear their artificiality upon their very 
 face. He cuts away the heather and creeping willow, 
 trims down the bents, and reduces the green to the 
 quality of the best-kept lawn. He may by these 
 means produce a course on which a record score 
 may be lowered by a stroke or two. But to the 
 Naturalist he merely appears to upset the balance 
 of Nature, the observation of which is one of the 
 keenest delights of the links. 
 
 There have not been wanting those who have 
 publicly expressed their regret at the change which 
 is passing over some of our leading courses. The 
 "Fairway" is mown and mown again. It widens 
 imperceptibly as the process is repeated, till the 
 outgoing course merges with the incoming. Not a 
 Bent dares to show its head in these ever-broadening 
 avenues. On some courses you must wander far 
 afield indeed before any serious obstacle of vegetable 
 origin penalises you. The policy of the green com- 
 
IX] GOLF LINKS 153 
 
 mittee seems to be to subordinate the guidance of 
 the ball to mere long driving. But it is possible 
 that the future may see a reversal of that policy by 
 the reintroduction, or the special preservation, of 
 Bents, Heather, and Whins so as artificially to 
 restore some of those natural penalties that the 
 green-keeper has so ruthlessly removed, or have 
 disappeared, may be, owing to the ordinary traffic 
 of the Links. Though we may regret their loss, 
 we may still remember that however deeply the 
 artificialities of the modern upkeep of the Links 
 may affect the surface and its vegetation, they do 
 little to modify the main contours of the ground. 
 These with their irregular undulations, their arbitrary 
 slopes and towering heights, are the true product of 
 natural forces, and the determining factor that has 
 influenced their origin and their form more than any 
 other is the vegetation of long ago. The individual 
 plants that shaped the Dunes may have passed into 
 natural decay, or have been swept out of existence 
 by the modern green-keeper, but still their record 
 remains registered for ages in the undulating surfaces 
 of the Links. 
 
CHAPTER X 
 
 GENERAL OUTLOOK ON THE FLORA 
 OF THE LAND 
 
 The foregoing Essays are apparently disjointed, 
 and aloof from one another. But just as a circle 
 may be defined by three or more detached points, 
 and be drawn so as to establish a clear relation 
 between them, so the subjects of the preceding 
 Chapters, isolated though they at first appear, may 
 be drawn together so as to give some general outlook 
 upon the vegetation around us. Ever since enquiry 
 into the Origin of living forms took shape in theories 
 of Evolution, the underlying principle has been 
 recognised that it is from the simpler organisms 
 that such origins are to be traced. The comparison 
 of these with the more complex has been held to 
 shed light on the genesis of the higher forms. On 
 the other hand, certain conditions and methods of 
 life are known to have led to simplification both 
 of structure, and of the cycle of events in the 
 completed life-story of the individual. Thus parasitism 
 leads to simplification of the organs of nutrition. 
 
CH. x] GENERAL OUTLOOK 155 
 
 Further, among Fungi some forms appear to omit 
 entirely certain stages which are shown in allied 
 forms. The life-history may thus be curtailed and 
 simplified. It is only with some limitation therefore 
 that the thesis is to be accepted that the simpler 
 organisms give a key to the problem of Descent. 
 Subject to such necessary limitations, the comparative 
 method may be adopted, and we may state a current 
 theory of the Origin of the Vegetation of the Earth 
 based upon such comparisons. As we do so we 
 may recognise how readily it accords with the 
 limited facts advanced in the foregoing pages. 
 
 A great body of evidence indicates that the 
 origin of Plant-Life on Land was from aquatic 
 surroundings. The water-problem is at the base 
 of the whole physiology of Land plants. There 
 is no requirement so imperative, and no adaptation 
 so exact, as that for the supply and the control of 
 the water which forms so large a constituent of 
 any Plant of the Land. The stability of the plant 
 while young, as well as the functional activity of 
 each cell of its body during life, depend upon a 
 balance of gain and loss of water being duly 
 maintained. The relative ease of aquatic plants as 
 regards their water-supply, compared with the almost 
 desperate shifts of many terrestrial plants, suggests 
 with some cogency that the latter is the derivative 
 and specialised, the former the primitive habitat. 
 
156 PLANT-LIFE ON LAND [CH. 
 
 But far the most convincing evidence is that derived 
 from the details of propagation. The simpler denizens 
 of the water commonly show a phase where detached 
 cells are motile in water, as we have seen in the case 
 of Ulva and Ulothrix (Chapter II). Such an 
 incident figures in the life-cycle of all the simpler 
 Land plants. It is seen in Mosses, Liverworts, Ferns 
 (Chapter III), Club-Mosses, and Horsetails. None 
 of these live through their normal life without 
 dependence at one critical point upon external fluid 
 water as the medium for that motility. In this they 
 are believed to show traces of their ultimate aquatic 
 origin still preserved. It is not till we reach the 
 Higher Flowering plants that freedom from that 
 embarrassing condition of life is seen : for in them 
 fertilisation is by a pollen-tube, and external fluid 
 water is no longer necessary for the process. In 
 this respect the Flowering plants have become in 
 the fullest sense Plants of the Land. 
 
 Further than this it has been suggested (Chapter 
 II) that the motile stage of Algae may itself have 
 been actually the primitive state for them, and have 
 preceded that non-motile phase which is usually 
 styled the "plant." The ultimate ancestors of the Sea- 
 weeds were probably detached and motile organisms, 
 like the simple Flagellates of the present day. It is 
 a very reasonable, and even physiologically a probable, 
 view that primitive life was like them naked and 
 
x] GENERAL OUTLOOK 157 
 
 unicellular, motile and unattached. The first step 
 was probably that of encystment in a cell-wall. In 
 some primitive forms this was soft and gelatinous, 
 and motility was retained, as is seen in Volvox. 
 But commonly the wall formed a firm coat, and 
 non-motility naturally followed. This state proved 
 effective since it conduced to protection, and offered 
 no obstacle to self-nutrition, while it led readily 
 enough to the constitution of organisms composed 
 of more than a single cell. So long as such fixed 
 and multicellular organisms grew submerged or 
 between tide-marks, the further working out was 
 not difficult. Since mechanical stability and conduc- 
 tion of water were not pressing necessities, such 
 plants were free to attain great size, and this is 
 fully realised in the larger Algae. Spread of the 
 species was sufficiently provided for by water-carriage, 
 either in the form of motile or non-motile germs. 
 In fact a non-motile and attached habit of the whole 
 plant presents few disabilities and definite advantages 
 to plants growing in water. Hence the extent and 
 the success of the Seaweed Flora as we know it. 
 
 But it was otherwise with the non-motile vege- 
 tation which, originating as we believe from some 
 Algal source, spread to the Land, and developed 
 into the terrestrial Flora as we see it to-day. Such 
 plants are exposed in part or even wholly to an 
 atmosphere seldom saturated with moisture, and 
 
158 PLANT-LIFE ON LAND [CH. 
 
 for the most part relatively dry. A fixed habit is 
 obligatory for them in order to secure their supply 
 of water and soluble salts from the soil. The 
 development of special tissues for conduction and 
 for mechanical strength followed, and these are seen 
 in a simpler type in the Mosses, but in quite an 
 advanced condition in the Ferns and Horsetails. 
 It was, however, on the propagative methods that 
 the change of habitat from water to land brought 
 special disabilities. The absence of external fluid 
 water, except at intervals, put a check upon pro- 
 pagation by self-motile germs. Fertilisation by 
 spermatozoids motile in water could only take 
 place at times of rain or copious dew. As a set 
 off" against this the formation of numerous detached 
 spores, dry and dusty when ripe, and thus readily 
 transferred by the wind, became a marked feature 
 of this primitive vegetation of the Land. It is seen 
 carried to high perfection in Mosses and Ferns 
 (Chapter III). By this means, while sexual repro- 
 duction in such plants was necessarily an uncommon 
 event, a vast number of individuals might be produced 
 as a consequence of a single fertilising act. This 
 arrangement provided adequately for the maintenance 
 of the race, and for the spread of its individuals. 
 The i:)ro vision for intercrossing was, however, deficient. 
 It is true that there is an attraction of tlie motile 
 sperm to the archegonium ; but the sphere of such 
 
X] GENERAL OUTLOOK 159 
 
 influence is restricted by the limits of the water- 
 medium within which it acts (Chapter III). Thus 
 what may be styled the primary vegetation of the 
 Land, including Mosses and Ferns and their allies, 
 constituted a true Land Flora as regards their 
 vegetative system, but their propagative method 
 was conservative and ineffectual for land-living plants. 
 It remained typical of their aquatic ancestry, and 
 sufiered from natiu-al restrictions on dry land. Such 
 a Flora might be styled in a sense amjihibial. 
 
 It remained for the Seed-plants to break loose 
 from these limitations, and to become a Land Flora 
 in the full sense of the term. The most important 
 change which they show is in tlie method of their 
 fertilisation by the pollen-tube. The pollen-grains 
 can be transferred from the stamen to the stigma 
 at any time, and dry conditions will even favour the 
 process, while the further growth of the pollen-tube 
 down the style is independent of external fluid water. 
 Thus the conservative restriction which hampered 
 the primary vegetation of the Land was finally 
 removed. It has been seen that the Mosses and 
 Ferns and their allies are deficient in opportunity 
 for intercrossing, as a consequence of their aquatic 
 method of fertilisation. This disability also falls 
 away in the Seed-plants. They show as one of 
 their most popular and sensational features an 
 extraordinary facility in tlie use of external agencies 
 
160 pla:n^t-life on LA:^^D [ch. 
 
 for securing cross-pollination. The wind, occasionally 
 water, but chiefly animal agencies have been brought 
 into the service of intercrossing. The full armoury 
 of colour, of honey, and of scents, together with 
 elaborate mechanical devices, contribute to this end. 
 Their study has become almost a play-ground of 
 science. The flower has developed into a highly 
 specialised mechanism for the purpose of intercrossing. 
 First came the segregation of the nutritive and pro- 
 pagative regions of the originally non-specialised 
 shoot, by such steps as are illustrated among the 
 lower Vascular plants. The propagative region then 
 gradually assumed the features of the flower as it 
 is seen in such various forms at the present day 
 (Chapter IV). But while we recognise to the full 
 the beauty and the almost infinite variety of the 
 methods employed to secure cross-pollination, the 
 fact that stands behind them all, and is indeed their 
 ultimate justification, is the immobility of the plant, 
 so different from the ambulatory powers of the 
 higher animals. The plant cannot move as a whole 
 to seek its mate, and so if intercrossing is to take 
 place at all, external agencies must be pressed into 
 the service. 
 
 The same fact is the ultimate raison d'etre of 
 the varied methods of dispersal of seeds and fruits 
 (Chapter VII). It has been seen how great is the 
 fecundity of many land growing plants. But the 
 
X] GENERAL OUTLOOK 161 
 
 full eflPect of this cannot be gained unless the spores 
 and seeds be scattered, so that each shall have its 
 individual chance on germination. The plant being 
 immobile cannot effect this of its own motion. 
 External agencies are made available by various 
 adaptive features. It is again the wind, water- 
 currents, and animal agents which are employed in 
 overcoming this disability which follows so directly 
 from the fixed position of plants. Thus we see a strong 
 antithesis between the mobile animal and the immobile 
 plant, which may be traced back ultimately to their 
 differences of nutritive method. It is, however, 
 between the higher terms of the two series that 
 the distinction is most marked. Passing backwards 
 to the simpler, and presumably earlier forms, they 
 assimilate more nearly, till we find ourselves contem- 
 plating forms which occupy a borderland distinctive 
 of neither kingdom, and suggestive of a common 
 origin. 
 
 The spread of germs leads not only to the 
 maintenance of the numbers of the species but also 
 to the occupation of new sites. In fact vegetation, 
 as we see it, may be held to represent a balance 
 struck between the high capacity for increase of 
 the species involved, and the restrictive influence 
 of external circumstances. Examples have been 
 quoted where the former obtains the upper hand, 
 and a rapid spread of a species may be the result. 
 
 B. 11 
 
162 PLANT-LIFE ON LAND [CH. 
 
 The contrary balance leads to restriction or even 
 to extinction. It is in this light that the vegetation 
 of the Golf-Links may be viewed. It may be taken 
 as an example of the occupation of a barren area 
 (Chapter VIII). The fresh blown sand from the beach 
 is a 7iidus presenting from time to time a fresh 
 surface, austere but ready to receive. Doubtless 
 there is a natural selection among the many germs 
 that fall upon it, and only those suited to the 
 situation obtain a permanent hold. Putting the 
 prime formers of the Dune on one side, the variety 
 of the species that bring about the conversion of 
 the Dunes from the White or shifting state to the 
 permanent condition of the Grey Dune is great. The 
 observation of it gives the opportunity for the study 
 of a new Flora in the making, aiid it may be noted 
 as we walk the Links, how many are the species 
 whose germs are called into existence, and how few 
 are physiologically chosen. 
 
 In drawing this Series of Sketches to a close, 
 it must be clearly understood that no attempt has 
 been made to follow with exactitude the Evolutionary 
 History of Plants as we see them. What has been 
 attempted has been to illustrate along various lines 
 of thought, each suggested by common features of the 
 country, the outlook of Modern Botany. Each of 
 these lines converges in one way or another upon 
 the central problem of descent. The most prominent 
 
X] GENERAL OUTLOOK 163 
 
 result is to bring into a clear light the importance of 
 the relation of plants to water. In particular, attention 
 has been drawn to the water-problem as it affects 
 Land-plants. It is indicated that the acute incidence 
 of it is a consequence of the migration of organisms 
 originally aquatic to the land. In fact, a broad com- 
 parison of vegetation as a whole shows that the 
 Flora of the Land is not primary, but secondary. 
 Its constituents have found it necessary to adapt 
 themselves to the atmospheric surroundings which 
 they have adopted. This has not always been suc- 
 cessfully carried out. The adaptation has sometimes 
 been hampered by an almost inexplicable conservatism. 
 It is the study of such features which has given the 
 clearest clues. In them we may find evidence, still 
 preserved, of that greatest of migrations in an age 
 long past, viz. the transition of Plant-life from Water 
 to the Land. 
 
INDEX AND GLOSSARY 
 
 Aconitum (Monkshood), 93, 116 
 
 Acropera, a genus of Orchidaceae, 
 106 
 
 " Adlerfarn," the German name 
 for the common Bracken, de- 
 rived from the double-eagle 
 seen in section of the leaf- 
 stalk, 33 
 
 Adventitious buds, additional 
 buds formed at points not in 
 the normal sequence, 132, 142 
 
 Agencies for effecting distribu- 
 tion of germs, 98, 113, 161 
 
 Agrostis, a genus of Grasses, often 
 called the "Bent"; but the 
 "Bent" of golfers is Ammo- 
 phila, 140 
 
 Aira, a genus of Grasses, 140 
 
 Algae of the sea and freshwater, 
 13 ; blue-green, 113 ; green, 
 113; red, 113; brown, 113 
 
 Algal Flora, term used collectively 
 for Algae of the coast or fresh- 
 water, 13, 157 
 
 Alternation of generations, the 
 alternating succession of two 
 phases in the life-history of 
 plants, as seen in Mosses and 
 Ferns, etc., 45 
 
 Ammophila arimdinacea, see 
 Marram Grass 
 
 Angiopteris, a genus of very 
 ancient Ferns, 107 
 
 Animal agency, 96 
 
 Animals, distribution by, 99, 
 113; movements of, 82; mo- 
 bility of, 161 ; predatory attack 
 by, 89 
 
 Annulus, a ring of hardened cells, 
 which acts as a spring in open- 
 ing the sporangium of Ferns, 
 and scattering the spores, 38 
 
 Antheridium, the male organ of 
 Ferns, and other land-growing 
 plants, which produces the 
 spermatozoids, 39, 40, 41, 71 
 
 Antipodal cells, a group of cells 
 situated at the base of the 
 embryo-sac in the Higher Flow- 
 ering Plants, 73 
 
 Archegonium, the female organ 
 in Ferns and other land- 
 growing plants: it produces 
 the ovum or egg, 39, 40, 42, 
 43 
 
 Asclepiad, member of the Ascle- 
 piadaceae, a family of the 
 Higher Flowering Plants, 89 
 
 Ascophyllum nodosum, a common 
 Brown Tangle (Alga) of our 
 coast, growing about half-tide 
 mark, 16 
 
INDEX AND GLOSSARY 
 
 165 
 
 Aspergillus, a genus of Moulds, 
 including the common olive 
 green Mould on Bread, 107 
 
 Athyrium filix-foeviina, the Lady 
 Fern, 1*07 
 
 Axillary buds, buds which arise 
 in the axil or angle between 
 the leaf-stalk and the axis, 136 
 
 Bacillus subtilis, the common 
 Hay Bacillus, one of the Bac- 
 teria, 108 
 
 Bacteria, productivity of, 108, 
 113, 115 
 
 "Barchan," a peculiarly shaped 
 sand-hill, seen in the Libyan 
 Desert, (Fig. 19), 123, 124 
 
 Batrachospermum, a genus be- 
 longing to the red Algae, which 
 grows in freshwater streams, 13 
 
 Beach, 12, 128 
 
 Beech tree, storage in the com- 
 mon, 110 
 
 Beet {Beta maritima), native on 
 the coast, 122 
 
 Begonia, protected by acid taste, 
 89 
 
 Bennettitales, a family of fossil 
 plants allied to the Cycadaceae, 
 63 
 
 Bents, a name for certain Grasses, 
 but not always strictly applied. 
 The golfer's "Bent" is the 
 " Marram," which see, 147, 
 152 
 
 "Blow-out," a term applied to 
 the hollows scooped out of 
 sand-hills by the action of the 
 wind, 151, 152 
 
 Bracken Fern {Pteridium aquili- 
 num), 29, 31 
 
 Buds, adventitious, 132, 142 ; 
 axillary, 136 
 
 Burnet Rose (Rosa spijiosissima), 
 
 142 
 Buttercup {Ranunculus), (Fig. 10) 
 
 Cactaceae, self-protection of, 90 
 
 Calyx, the outermost series of 
 floral organs, 53 ; origin of, 64 
 
 Cardoon Thistle, dispersal of 
 its fruits, 114 
 
 Carpels, the innermost series of 
 floral organs, 53 
 
 Carrot, 122 
 
 Cell-division, the common pro- 
 cess by which cells are multi- 
 plied in plants, 19 
 
 Cell-wall, 18, 19, (Fig. 18) 85, 
 157 ; permeability of, 84 
 
 Cephalanthera, a genus of Or- 
 chids, 106 
 
 Chlorophyll-body, green coloured, 
 embedded in protoplasm of the 
 cell, 18 
 
 Cilia, threads of protoplasm at- 
 tached to certain free cells of 
 water plants : by their active 
 lashing movements they cause 
 motion in the cells that bear 
 them, 20, 41, 78 
 
 Cladonia, a genus of Lichens, 
 140 
 
 Clavaria, a genus of Fungi, 140 
 
 Climate, risks from, 90 
 
 Clover, 140 ; clover and cats, 116 
 
 Club-Mosses, a very ancient 
 family of plants, represented 
 by the livmg genus Lycopo- 
 diujn, 45, 53 56, 156 
 
 Colouring, physiological meaning 
 of, 14 
 
 Couidiophore, a fungal filament 
 that bears propagative cells 
 (conidia), 107 
 
 11—3 
 
166 
 
 INDEX AND GLOSSARY 
 
 Conifers, the family of Pines and 
 Firs, 5 
 
 Convolvulus Soldanella, the Con- 
 volvulus of sandy shores, 129 
 
 Cord Moss [Fuuaria hygrome- 
 trica), 114 
 
 Corolla, collective name for the 
 petals of flowers, 53 ; origin 
 of, 64 
 
 Cotton grass {Eriophorum), a 
 genus of Sedges, 140 
 
 Couch grass {Triticum repens), 
 129 
 
 Creeping Willow {Salix repens), 
 140, (Fig. 27) 149 
 
 Cross-fertilisatiou, 91 
 
 Cross-pollination, 92, 160 
 
 Crystals, protection by, 90 
 
 Culbin sands, 138 
 
 Ct/athea dealbata, a large Tree 
 "Fern, 107 
 
 Cycadeoidea, a Mesozoic fossil; 
 flower of, 65 
 
 Cycads, an ancient family of 
 Fern-like plants, bearing naked 
 seeds : now only sparsely re- 
 presented, 63, 78 
 
 Cycle of Life, the whole series of 
 events, sometimes varied and 
 complex, comprised in the life 
 of the individual, 22, 44 
 
 Cytoplasm, the protoplasmic body 
 of the cell, exclusive of the nu- 
 cleus and plastids, 72 
 
 Danaea, a genus of Ferns of an- 
 cient type, 107 
 
 Darwin, 82, 91, 92, 105, 106, 114, 
 116 
 
 Depth, distribution of Algae in 
 the sea with regard to, 13 
 
 Diatoms, minute unicellular Al- 
 gae, 113 
 
 Disc of attachment, as seen at 
 base of many Algae, 17, 18 
 
 Distribution, agencies for effect- 
 ing, 98, 113, 161 ; by animals, 
 99, 113 
 
 Dock {Rumex), 89 
 
 Dunes, 122, 130, (Fig. 22) 131, 
 146 
 
 Dune-Flora, 134, 138, 140 
 
 Egg-apparatus, a group of three 
 cells, one of which is the egg 
 itself, attached to the apical end 
 of the embryo-sac in the Higher 
 Flowering Plants, 72, (Fig. 15) 
 73 
 
 Egg-cell or ovum, the female cell 
 which is to be fertilised, 42, 43, 
 73, 94 
 
 Elimination of weaklings, 118 
 
 Embryo, the product of fertilisa- 
 tion, 42 
 
 Embryo-sac, a large cell (mega- 
 spore) embedded in the tissue 
 of the ovule of the seed-bearing 
 plants, in which the ovum and 
 ultimately the embryo are pro- 
 duced, 72, (Fig. 15) 73 
 
 Encysted cell, 22, 24, 157 
 
 Encysted state, secondary, 27 
 
 Encystment, the surroundmg of 
 the protoplasm by a covering 
 cell-wall, 84, 86, 99, 157 
 
 Enteromorplia, a genus of green 
 Algae, 18 
 
 Ernst, A., 113 
 
 Evolutionary tree, blind branches 
 of, 28 
 
 Explosive fruits, 99 
 
 Eye-spot, 21 
 
 Female cell, 69 
 
 Ferns, life-cycle of, 44 ; pro- 
 
INDEX AND GLOSSARY 
 
 167 
 
 ductivity of, 107; wind-borne 
 
 germs of, 113 
 Fertilisation, 42, 45, 68, 73, 74, 
 
 75, 156 
 Filamentous structure, 19 
 Findhorn river, 139 
 Fixed position, secondary, 28 
 Flagellates, certain unicellular 
 
 organisms, motile in water, 
 
 24, 156 
 Fleabane {Erigeron), 106 
 Flies, as bearers of spores, 117 
 Flixweed {Sisymbrium sophia), 
 
 106, 108 
 Flora of the land, 48, 163 ; new, 
 
 112 ; of the sea, 13 
 Flower, 48, 49, 53; parts of, 51, 
 
 (Fig. 10) 53 ; origin of, 55, 67 
 Flowering Plants, 47, 55, 70, 77, 
 
 156 
 Fluctuating variations, 119 
 Foliage-shoot, distinct from 
 
 flower, 50, 54 
 Foot, the part of the embryo in 
 
 Ferns and some other plants, 
 
 which serves as a haustorium 
 
 or sucker, 39 
 Fucus platycarpus, one of the 
 
 common brown Tangles (Algae) , 
 
 16 
 Fungi, 140; productivity of, 107 
 Funiculus, the stalk of the ovule, 
 
 72, (Fig. 15) 73 
 
 Gametes, the sexual cells, un- 
 differentiated in some of the 
 lower forms, but distinct as 
 male and female in all the 
 higher, 21, 23, 26, 72, 78; in- 
 equality of, 26; origin of, 25 
 
 Gametophyte, that stage or phase 
 in the life-history which bears 
 the gametes, or sexual cells. 
 
 In the Fern it is represented 
 by the prothallus, 46 
 
 Generative cells, the male ga- 
 metes in the pollen-tube of a 
 Flowering Plant, (Fig. 14) 71 
 
 Geometrical ratio of increase ; for 
 explanation see p. 105 
 
 Germs, detachable living products 
 of the plant, used generally for 
 spores, seeds, or other bodies 
 from which a new individual 
 may spring, 102, 109 ; transfer 
 of, ' 104, 111 ; chances of life 
 of, 110; over-production of, 
 117 ; spread of, 161 
 
 Ginkgo, the Maiden Hair Tree of 
 Japan, 78, 79 
 
 Goebel, K., 116 
 
 Goethe, 54, 67 
 
 Golf Links, 145 
 
 Gorse or Whin {Ulex europaeus), 
 142, 153 
 
 Grey Dune, that type of Dune in 
 which the sand is covered by 
 a coat of vegetation, 140, 142, 
 147 
 
 Ground-water, 138 
 
 Gulf Weed (SdrgassiDii haccife- 
 rum), a form of Tangle, which 
 is found floating freely in large 
 quantities in the neighbour- 
 hood of the Gulf of Florida, 87 
 
 Gymnosperms, a large body of 
 primitive Seed Plants, includ- 
 ing the Pines and Firs and 
 Cycads, characterised by having 
 their seeds exposed, 78 
 
 Gynoecium (p. 72), the central 
 part of the flower in the Higher 
 Flowering Plants, composed of 
 the carpel or carpels, and en- 
 closing one or more ovules : 
 e.g. Fig. 15, p. 73 
 
168 
 
 INDEX AND GLOSSARY 
 
 Halophytes, plants which grow 
 where the water contains salt ; 
 the effect upon them is seen in 
 their fleshy habit, 129 
 
 Hard Fern {Lomaria spicant), 60 
 
 Heath {Erica), 142 
 
 Henbane {Hyoscyamus niger), 
 106, 108 
 
 Hermaphroditism, the existence 
 of the male and female organs 
 on the same individual, 97 
 
 Higher Plants, generally equiva- 
 lent to Seed-bearing Plants, 
 47, 50, 70, 156 
 
 Himanthalia lorea, one of the 
 common brown Tangles of the 
 coast, 16 
 
 Hofmeister, W., 56 
 
 Horsetails, a very prevalent 
 family of plants in early geo- 
 logical times, but now repre- 
 sented only by the genus 
 Equisetum, 45, 53, 56, 156 
 
 Horticulture, 5 
 
 Humble Bees, 116 
 
 Immobility of Plants, 82, 89, 96, 
 157 
 
 Increase, geometrical ratio of, 105 
 
 Indusium, a protective covering, 
 usually thin and membranous, 
 which overarches the sporangia 
 in Ferns, 35, (Fig. 6) 37, 38 
 
 Inflorescence, a branch-system in 
 the Higher Plants, specially de- 
 veloped for bearing flowers, 
 135 
 
 Insects, attraction of, 64 
 
 Insect-agency, 70 
 
 Integuments, the outer coats of 
 the ovule, 72, (Fig. 15) 73 
 
 Internode, the length of stem 
 intervening between the inser- 
 
 tion of two successive leaves, 
 136 
 
 Intra-cellular movement, the 
 movement of the protoplasm 
 of the living cell within its 
 cell-wall, 82, (Fig. 18) 85 
 
 Ipomoea Pes-caprae, a member of 
 the Convolvulus family, preva- 
 lent on tropical shores, 129 
 
 Kaulfussia, a genus of Ferns, 
 
 107 
 Kerner, A., 106, 108 
 King Charles' oak, 33 
 Krakatau, Island of, 112 
 
 Ladies bedstraw {Galium verum), 
 
 140 
 Lake Michigan, 139 
 Land Flora, 159, 163 
 Land, vegetation of, 45, 87, 156, 
 
 158 
 Lantana, a genus of Verbenaceae, 
 
 dispersal of, 114 
 Leaf, fall of, 91 
 Lemanea, a genus belonging to 
 
 the Red Algae, which grows in 
 
 mountain streams, 13, 14 
 Libyan Desert, 123, 124 
 Lichens, 140 
 Lilium Martagon, Turk's Cap 
 
 Lily, 71 
 Ling or Heather {Calluna vul- 
 garis), 142, 153 
 Links, 124, 126 
 Linnaeus, 106 
 Liverworts, 45, 156 
 Lopsided or dorsiventral forms, 
 
 of shoot or flower, 51 
 Lotus, a genus of Leguminosae, 
 
 140 
 Lovage {Ligusticum scoticum), one 
 
 of the Umbelliferae, 122 
 
INDEX AND GLOSSARY 
 
 169 
 
 Lijcopodium Selago, a common 
 Club Moss, 60, (Fig. 12) 61, 
 62 
 
 Lyme grass {Elymus arenarius), 
 137, 144 
 
 Magnolia, 66 
 
 Maiden-hair Tree (Ginkgo biloba), 
 80 
 
 Male cell, 69 
 
 Male Fern [Nephrodium filix- 
 mas), 31, 35, 59, 60, " and 
 Figs. 5, 6, 7 
 
 Mammoth Trees [Sequoia), 88 
 
 Marattia, an ancient genus of 
 Ferns, 107 
 
 Marram Grass {Ammophila arun- 
 dinacea), 124, (Fig. 23) 133, 
 134, (Fig. 24) 187, 144, 147 
 
 Maviston, (Fig. 25) 141, (Fig. 26) 
 143 
 
 Maxillaria, a genus of Orchi- 
 daceae, 106 
 
 Memorised records, 120 
 
 Metamorphosis, 49, 54, 63 
 
 Mice, 116 
 
 Micro-zoospores, small free cells 
 of certain Algae, motile in 
 water, but not sexual, 20, 21 
 
 Mimosa, the Sensitive Plant, 
 movements of, 82 
 
 Molecular movement, such move- 
 ments as are not in mass, but 
 molecule by molecule, 82 
 
 Monkshood (Aconitum), 93, 116 
 
 Monostroma, a genus of green 
 Algae, 18 
 
 Moray Firth, 138 
 
 Moss, 45, 140, 156 
 
 Moulds, productivity of, 107, 114 
 
 Mouse-ear {Hieracium pilosella), 
 140 
 
 Movement, 82, 156 
 
 Miiller, H., 68, 92 
 Mutations, 119 
 
 Name, specific, 4 
 Natural selection, 118 
 Nephrodium filix-mas (common 
 
 Male Fern), 31, 35, 59, 60, and 
 
 Figs. 5, 6, 7 
 Nucellus, the central body of the 
 
 ovule in Seed Plants ; it is 
 
 covered by the integuments 
 
 and encloses the embryo-sac, 
 
 72, (Fig. 15) 73 
 Nucleus, a clearly defined and 
 
 highly refractive part of the 
 
 protoplasm of the cell, 18, 72, 
 
 (Fig. 18j 85 
 Nutrition, method of, 83, 88 ; 
 
 precedes propagation, 50 
 
 Orache {Atriplex), 129 
 
 Orchids, 51, 67, 106 
 
 Orchis, 70 
 
 Orchis maculata (common spotted 
 
 Orchis), 106 
 Osmunda regalis (Royal Fern), 
 
 60 
 Ovary, the part of the flower 
 
 which contains and protects 
 
 the ovules, 72, (Fig. 15) 73 
 Ovule, the body which developes 
 
 into the seed after fertilisation, 
 
 52, 53, 72, (Fig. 15) 73 
 Ovum, the female cell, 42, (Fig. 9) 
 
 43,72 
 
 Parenchymatous cell, a cell 
 usually thin-walled, with liv- 
 ing protoplasm, approximately 
 cubical or oblong, (Fig. 18) 85 
 
 Pea, 51 
 
 Pelvetia, a genus of Brown Sea- 
 weeds, 16 
 
170 
 
 INDEX AND GLOSSARY 
 
 Penzig, 0., 113 
 
 Pilobolus, a Mucorineous Mould, 
 which grows on dung, 117 
 
 Pinnae, segments of leaves, 33 ; 
 fertile, 65 
 
 Pistil, the central region of the 
 flower, which bears and pro- 
 tects the ovules, 72 
 
 Plankton, a general term for the 
 floating life of the sea, or of 
 freshwater, 72, 86 
 
 Plant, the, 23, 156 ; immobile, 
 161 ; movements of,. 82, 156 
 
 Plant-life on Land, origin of, 155 
 
 Plant-population, 102 
 
 Pollen, the detachable male spores 
 of Seed-plants, 52, 70, (Fig. 14) 
 71 
 
 Pollen-grain, (Fig. 14) 71 
 
 Pollen-tube, the tube which grows 
 out from the pollen-grain, and 
 traversing the style, conveys 
 the sexual cells or gametes 
 to the ovule, (Fig. 14) 71, 
 (Fig. 15) 73, 74, 77, 156 
 
 Pollen-sac, the chamber in which 
 the pollen-grains are produced. 
 There are usually four of them 
 on each anther, 52, 53, 70 
 
 Pollination, the transfer of pollen 
 from the anther to the re- 
 ceptive surface of the stigma, 
 or, in Gymnosperms, directly to 
 the ovule, 68, 95, 160 
 
 Pollination, difliculty of, 91 ; 
 agents for effecting, 96 
 
 Pollinating mechanisms, 69, 160 
 
 Polygonum convolvulus, a climb- 
 ing Dock, common in corn 
 fields, 73 
 
 Polypodium aureum, a common 
 cultivated Fern, 107 
 
 Population of plants, 102 
 
 Position, fixity of, 81, 87 
 
 Propagation, period of, 19 
 
 Prothallus, the sexual stage, or 
 gametophyte, as in a Fern, 
 (Fig. 7) 39 
 
 Protoplasm, movements of, (Fig. 
 18) 85 
 
 Protoplast, the whole body of 
 living protoplasm belonging to 
 a single cell, 18, 19, 84, 99 
 
 Pteridium aquilinum, the Com- 
 mon Bracken, 30 
 
 Pteris aquilina, the older synony- 
 mous name for the Bracken 
 Fern, 30 
 
 Puff-balls, 140 
 
 Eabbits, 150 
 
 Race, maintenance of, 97 ; spread 
 of, 97, 161 
 
 Radish {Baphanus), 106 
 
 Raw Material of Golf Course, 
 (Fig. 27) 149, 150 
 
 Receptacle, the enlarged out- 
 growth of the Fern leaf on 
 which the sporangia are in- 
 serted, 37 
 
 Rest Harrow {Ononis spinosa), 142 
 
 Rhizoid, a cellular outgrowth 
 which has an absorptive func- 
 tion, 20, 39 
 
 Rhizome, an underground stem, 
 as in the common Bracken, 
 (Fig. 4) 31, 44 
 
 Roots, attachment of, 87 
 
 Royal Fern (Osmunda regalis), 60 
 
 Rue, Meadow (Thalictrum), 96 
 
 Runners, horizontal underground 
 stems, 132 
 
 Rush (Juncus), 140 
 
 Salt-wort {Salsola), 127, 129, 
 (Fig. 21) 132 
 
INDEX AND GLOSSARY 
 
 171 
 
 Salvia (Sage), 71 
 
 ^SLmphire (Crithnium viaritimum) , 
 
 122 
 Saud, its composition, 12, 126 ; 
 
 shifting, 12 ; binders, 129, 130, 
 
 136, 147 ; Dunes 122, (Fig. 22) 
 
 126 
 Sand-sedge [Garex arenaria) , 129, 
 
 138 
 Sand-streamers, (Fig. 20) 125, 
 
 128 
 Sargassum, the Gulf Weed, a 
 
 brown Tangle, 87 
 Scotch Fir [Pinus sylvestris), (Fig. 
 
 25) 139 
 Sea-blite {Suaeda), 129 
 Sea-buckthorn (Hippophae rham- 
 
 noides), 142 
 Sea-couch-grass [Triticum jim- 
 
 ceum), 129, 138 
 Sea-kale {Crambe maritima), 122 
 Sea-lettuce {Ulva), 16 
 Sea-rocket {Cakile maritima), 129 
 Seaweeds, brown, green, and red, 
 
 13, 14, 16 
 Seaweeds, coralline, 12 
 Seaweeds, nutrition of, 15 
 Sedges, members of the family of 
 
 Cyperaceae, 140 
 Seeds, distribution of, 97 
 Seed-plants, 47, 77 
 Seed-plants, earliest, 95 
 Self-nutrition, period of, 19 
 Self-pollination, 97 
 Self-protection of plants, 89 
 Sequoia, Mammoth Trees of Cali- 
 fornia, 88 
 Sewage impurities, 16 
 Sex, differentiation of, 25, 53 
 Sexuality, origin of, 25, 27 
 Sexual organs, 40 
 Sexual propagation, 93, 94 
 Sexual zooids, 21 
 
 Sheep, 150 
 
 Sheep's fescue [Festuca ovina), 140 
 
 Shepherd's purse (Capsella), 106 
 
 Shield fern {Nephrodium filix- 
 mas), 31, 35, 107 
 
 Shifting Dunes, 132, 138, (Fig. 25) 
 139, 140, (Fig. 26) 143, 147 
 
 Silica, 12 
 
 Silver weed {Potentilla anserina), 
 129 
 
 Snails, attacks by, 90, 92 
 
 Sorus, one of those groups of 
 sporangia, seen on the under 
 surface of Fern-leaves, (Fig. 5) 
 35, 37, 38 
 
 Specialisation of study, 11 
 
 Species, new, 2 
 
 Spectrum, 14 
 
 Spermatozoids male fertilising 
 cells, motile in water, (Fig. 8) 
 41, 42, 76, (Fig. 16) 77, (Fig. 
 17) 79, 94 
 
 Sperm-cells, which give rise to 
 spermatozoids, (Fig. 8) 41 
 
 Splachnaceae, a family of Mosses, 
 which grow on dung of herbi- 
 vorous animals, 116 
 
 Sporangium, a capsule-like organ 
 which bears one or usually 
 numerous spores, (Fig. 6) 37, 
 38, 52 
 
 Sporangium, abortion of, 63 
 
 Spores of Fern, 37, 38, 52; dis- 
 semination of, 40, 45 ; germi- 
 nation of, 40 
 
 Sporophyte, the phase or genera- 
 tion in the life-history which 
 bears the spores, and is non- 
 sexual, 46 
 
 Sprengel, K., 68, 89 
 
 Spurge {Euphorbia), 89 
 
 Stahl,E., experiments with snails, 
 90 
 
172 
 
 INDEX AND GLOSSARY 
 
 stamen, that part of the flower 
 which bears the pollen-sacs, 
 usually four in number, 53, 70 
 
 Staminate disc of Cycadeoidea, 
 (Fig. 13) 65 
 
 Sterilisation, theory of, 58, 63 
 
 Stigma, the receptive surface for 
 the pollen, (Fig. 15) 73 
 
 Stock, or rhizome, an under- 
 ground stem, 30 
 
 Storage of material, 34, 50 
 
 Struvea, a genus of green Algae, 15 
 
 Style, the part of the pistil below 
 the stigma, which is often elon- 
 gated, (Fig. 15) 73 
 
 Sweet rush (Acorus), 90 
 
 Swimming-free stage, 25, 28, 156 
 
 Talipot Palm (Corypha), 110 
 
 Tangles, brown Algae, 16 
 
 Teesdalia, a genus of Cruciferae, 
 140 
 
 Terminology, 6 
 
 Tobacco (Nicotiana), 106 
 
 Transition from aquatic to terres- 
 trial, 77, 156 
 
 Treub, M., 113 
 
 Ulva lactuca, sea lettuce, (Fig. 1) 
 
 17 
 Ulva latissima, 16, 156 
 Ulothrix, a tilamentous green 
 
 Alga, 18, 156 
 Ulothrix zonata, (Fig. 2) 21, (Fig. 
 
 3) 28 
 
 Vacuole, pulsating, (Fig. 2) 21 
 Variations, fluctuating, 119 
 Vegetation of the earth, 27 ; ori- 
 gin of, 155 
 Vegetative cell, (Fig. 14) 71 
 Vetch {Vicia), 140 
 
 Volvo.v, a free-swimming green or- 
 ganism of freshwater, 157 
 
 Water, distribution of germs by, 
 98, 113 ; medium of fertilisa- 
 tion, 79 
 
 Water- problem, or water-relation, 
 45, 155, 163 
 
 White dunes, those in which the 
 vegetation does not cover the 
 surface, and the sand gives 
 the prevalent colour, 130, 138, 
 140, 147 
 
 Whitlow-grass {Erophila verna), 
 140 
 
 Wieland, G. K., 65 
 
 Wild Cabbage {Brassica olera- 
 ceae), 122 
 
 Wind, distribution by, 98, 113 ; 
 ripples on sand produced by, 125 
 
 Wolff, 54 
 
 Wood soriel {Oxalis acetosella), 89 
 
 Xerophytic specialisation, the 
 special structural development 
 of plants so as to fit them for 
 resisting extremes of drought 
 and heat, 134, 137, 142 
 
 Zamia Jioridana, one of the Cy- 
 
 cadaceae, 77 
 Zonation of seaweeds, 15, 16 ; 
 
 of vegetation of the shore, 81 
 Zooid, an independently motile 
 
 primordial cell, 20 
 Zoospores, motile propagative 
 
 cells consisting of naked pro- 
 toplasm, 20, 21, 23 
 Zygospore, the result of fusion of 
 
 two equal gametes, 23 
 Zygote, the result of fusion of two 
 
 gametes, 22, 23, 74 
 
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