®llf 1 S. 1. ItU aiibrars w Nnrtb (Earoltna i>tatp (ColUgf SB123 V98 N.C STATE UNIVERSITY DH HIL S00254388 U m — t\m WAY 2 Date Due DEC 2 1 1995:i 193B He -am APR 9 r19H: i < r?'^ k^ awstoioM ^ .%. MAR^I |90J i ' j i'^Uik^ PLANT-BREEDING jr COMMENTS ON THE EXPERIMENTS OF NILSSON AND BURBANK HUGO DE VRIES PROFESSOR OV BOTANY IN THE UNIVERSITY OF AMSTERDAM M CHICAGO THE OPEN COURT PUBLISHING CO. London: Kegan Paul, Trench, Trubner & Co., Ltd. 1907 Copyright by THE OPEN COURT PUBLISHING CO. 1907 PREFACE Under the influence of the work of Nilsson, Burbank, and others, the principle of selection has, of late, changed its meaning in practice in the same sense in which it is chang- ing its significance in science by the adoption of the theory of an origin of species by means of sudden mutations. The method of slow improvement of agricultural varieties by re- peated selection is losing its reliabiUty and is being supplant- ed by the discovery of the high practical value of the ele- mentary species, which may be isolated by a single choice. The appreciation of this principle will, no doubt, soon change the whole aspect of agricultural plant breeding. Hybridization is the scientific and arbitrary combination of definite characters. It does not produce new unit-char- acters; it is only the combination of such that are new. From this point of view the results of Burbank and others wholly agree with the theory of mutation, which is found- ed on the principle of the unit-characters. This far-reaching agreement between science and prac- tice is to become a basis for the further development of practical breeding as well as of the doctrine of evolution. To give proof of this assertion is the main aim of these Essays. Some of them have been made use of in the delivering of lectures at the universities of California and of Chicago during the summer of igo6 and of addresses before various audiences during my visit to the United States on that oc- casion. In one of them (II. D.), the main contents have fl / ^n I >*k (K^ vi PREFACE been incorporated of a paper read before the American Philosophical Society at their meeting in honor of the bi- centennary of the birth of their founder, Benjamin Franklin, April, 1906. The results of Xilsson have been published only in the Swedish language; those of Burbank have not been de- scribed by himself. IMy arguments for the theory of mu- tation have been embodied in a German book, " Die Mu- tationstheorie" (2 vols. Leipsic, Veit & Co.), and in lectures given at the University of California in the summer of 1904, published under the title of "Species and \'arieties; their Origin by Mutation." A short review of them will be found in the first chapter of these Essays. LIST OF ILLUSTRATIONS Fig. Page. 1. A. The Oak-leaved Hazelnut {Corylus Avclla)ia laciniata), a natural sport of the ordinary hazelnut (B) ... 7 2. A. The toadflax (Li)iaria vulgaris). B, C. Its pyloric va- riety. D. A peloric flower on an ordinary specimen 12 3. A. The Double-flowered Corn-marigold {Chrysanthemum segetum plenum), an experimental mutation produced at Amsterdam, 1899. B. A flower-head of the original cul- tivated variety. C. The first result of selection. D. The first sign of doubling. E. A typical double flower-head . 13 4. The Experiment Garden in the botanical garden at Am- sterdam, covered with iron wire netting. Cultures of different Evening-primroses, some enclosed in bags for artificial pollination, 1904 ...... 15 5. Lamarck's Evening-primrose {Oenothera La'narekiana), a mutating species . . . . . . .17 6. Leaves of Lamarck's Evening- primrose (A), and of two of its mutants (B. Oen. lata. C. Oen. scintillans) . . 19 7. Mutants of the Evening-primrose. A. The red-veined form (O. rubrinervis) which is of the same size as the original species. B. and C. The dwarfish variety {Oen. nanella) . . . . . . . . .21 8. A flower-spike of the giant-mutant {Oenothera gigas), which originated in my garden, 1896 ..... 23 9. A flower-spike of the red-veined mutant {Oenothera rub- rinervis), which has been produced almost yearly by the parent species ........ 25 10. Dr. Hjalmar Nilsson, Director of the Swedish Agricultural Experiment Station at Svalof ..... 28 11. Poland wheat {Triticum polonicum) . . . . 2^ 12. A. Bellevue de Talavera-wheat, isolated by Le Couteur. B. Bearded white wheat, produced by Patrick Shirreff. C. Scjuarehead wheat, the most famous production of the same breeder ....... 32 13. A. Hallett's pedigree Chevalier barley. B. Hallett's pedi- gree wheat ....... 39 14. A reproduction of part of the first advertisement of pedi- gree wheat by F. F. Hallett. See the Times, London, June 18, Nov. 8 and Dec. 19, 1862 .... 40 15. The Swedish Agricultural Experiment Station at Svalof. Part of the campus and residence of the Director . . 49 16. The first building of the Swedish Experiment Station at Svalof, being the building of the Institute of the Swedish Seed-grain Society . . . . . . -53 viii PLANT-BREEDING Fio. Page. 17. The La])oratory of the Agricultural Experiment Station at Svalof, Sweden . . . . . . -57 18. The Dairy building of the Agricultural Experiment Station S\alof, Sweden ....... 59 19. Svalof Concordia pea, a most productive erect new variety of green peas, produced at Svalof .... 69 20. Svalof Pearl Summer wheat, not layering, early rijjening, with full-rounded kernels, that keep in the ears at har- vest time ........ 74 21. Ordinary Butt Summer wheat, for comparison with the im- proved variety of the previous figure .... 75 22-26. Five different types of new varieties of oats, pjroduced at Svalof. Fig. 22. Flag-oats .... 76 23. StitT-branched Svalof oats ...... 82 24. Svalof oats with spreading branches . . . -83 25. Svalof oats with bending branches .... 86 26. Svalof oats with weak branches ..... 87 27. A. Rye of Schlanstedt, produced by Wilhelm Rimpjau by slow repeated selection. B. Ordinary rj-e ... 97 28. Determination of centgener power of the progeny of individ- ual wheat plants at the Agricultural Experiment Station of Minnesota at St. Anthony Park. The progeny of each parent plant packed in a sack for separate harvesting. The Director, ]Mr. Hays in the first carriage, August, 1904 103 29. Breeding block of com which has been bred for high oil content on the farms of Funk Bros. Seed Co., Bloom- ington, 111. . . . . . . 108 30. Strength of individual stalks of corn on the breeding blocks of Funk Bros. Seed Co., Bloomington, 111. . . . 109 31. Different types of com. A. King Philipp, a variety of flint corn. B. Giant yellow dent corn. C. Rice popcorn. D. Dwarf popcorn ....... iii 32. A. Sweet corn, a cob with a staminate upper part and with some few kernels in top. B, C. Parts of a tassel of flint com bearing staminate spikelets and kernels . . 113 33. A highly ramified cob of corn . . . . .115 34. A. A male or staminate spikelet of corn. B. A pair of pis- tillate or female flowers. After models of Brendel, Berlin 119 35. A. Tassel of corn, flowering and producing the anthers from the spikelets. C. Cob in the husks, producing the silks 121 36. Sweet com, with scattered starchy kernels, produced by partial cross-pollination . . . . -123 37. Method of sacking ear and tassel in corn for hybridizing. Agricultural Experiment Station, Manhattan, Kansas . 125 ;^8. The hand pollination of corn in one of the breeding blocks on the farms of Funk Bros. Seed Co., Bloomington, 111. 126 39. Another view of hand pollination in breeding blocks of corn of Funk Bros. Seed Co., Bloomington, 111. . , 129 149 LIST OF ILLUSTRATIONS ix Fir- _ _ Page. 40. Growth of individual rows of corn on the breeding blocks of Funk Bros. Seed Co., Bloomington, 111. . . . 135 41. Rows from cobs of corn which have been self-fertilized and from those which have not been self-fertilized. The short rows being those self-fertilized. On the breeding blocks of Funk Bros. Seed Co., Bloomington, 111. . . . 13Q 42. Alternate detasseled rows of corn, at a later period of growth, on the breeding blocks of Funk Bros. Seed Co., Bloomington, 111. ....... 1 10 43. View in the experiment garden of Amsterdam, with cul- tures of corn and Evening-primroses .... 143 44. Twisted stems. A. Of a horsetail {Equisctiim Tchnatcja). B. C)ii\\evf\\(l\.e2i?,t\ {Dipsacus sylveslris) . . . 144 45. Sterile Corn, a special form of barren stalks without tassel and without ear. Originated in the botanical garden at Amsterdam, 1888 . ...... 145 46. Sweet corn. A. With straight rows. B. With oblique rows ......... 47 A kernel of corn cut longitudinally. H, E. Horny endo- sperm. M, E. Mealy or starchy endosperm. S. Scutel- lum. G, G. Germ. B. The young bud from which the stem will develop. R. Rootlet. After Frank . . 153 48. One of the breeding blocks of corn, which is being bred for high protein on the breeding blocks of Funk Bros. Seed Co., Bloomington, 111. Sept. 1906 . . . iSS 49. Luther Burbank of Santa Rosa, Cal. . . . -158 50. Burbank's farm at Santa Rosa, Cal., showing the residence, the greenhouse, the shed, and part of the Experiment gar- den. Photograph of the S. Pac. R. R. Co. . . " . 161 51. Experimental garden of Luther Burbank at Santa Rosa. A spineless cactus is seen along the fence. Cultures of Echeveria and other species in the foreground. Photo- graph of the S. Pac. R. R. Co. ..... 163 52. Luther Burbank in the garden before his house at Santa Rosa, Cal., receiving a visit of the author of these Essays (in the middle) and of Dr. G. H. Shull, of the Carnegie Institution (to the right) ...... 165 53. A field of improved Australian Star-tlowers on Burbank's home farm ........ 169 54. The improved Everlasting Australian Star-flower . • 171 55. A Hybrid Walnut reaching double the height of ordinary trees (Juglans Califoniica nigra) . . . -173 56. Extreme variability in the size of seedlings of hybrid wal- nuts in the second generation . . . . • 1 75 57. A row of hybrid walnuts before the residence of Luther Burbank at Santa Rosa. Photograph of t"he S. Pac. R. R. Co 177 58. Burbank Giant prune . . . . . . -179 X PLANT-BREEDING Fig. Page. 59. Burbank Sugar prune . . . . . . .181 60. The improved stoneless prune. The pit is not surrounded by any stony material, but by a jelly .... 190 61. Hybrid Cactus Seedlings at Santa Rosa, 1904 . . . 191 62. The Spineless edible Cactus, a hybrid between wild spine- less species and the cultivated varieties, growing along the fence of Burbank's farm at Santa Rosa . . . 193 63. A row of Shasta-daisies ...... 195 64. A flower-head of the fluted variety of the Shasta-daisy . 198 65. The crisp-leaved hybrid Heuchera . . . -197 66. The crisp-leaved hybrid Heuchera of Burbank. B, C. Normal type of Heuchera leaves .... 201 67. Extreme variability in the size of hybrid Callas . . 205 68. A. The plum and B. The brown-leaved Prunus Pissardi, two species grafted on the same tree . . . -215 69. Seedlings of the Spineless edible Cactus in their first and second years. !NIost of them are spiny, but the rare spineless ones will be selected for propagation . .227 70. Seedlings of the Spineless edible Cactus in their second year. 229 71. Extreme variability in the shape of the leaves of hybrid pop- pies. Second generation from a cross l)etween the Bride- variety of the opium poppy and the Oriental poppy . 231 72. A. The variety the Bride of the opium poppy. B. The wild species {Pa paver pilosiim). C. The hybrid of these two poppies . . . . . . -233 73. Flowers of Columbine, showing the spurs . . . 241 74. The deadly nightshade, or Atropa Belladonna. ' A. Brown flower, and B. Black fruit of the species. C. A twig of the yellow variety with pale flowers and yellow fruits . 243 75. T\\&\ox\g-\cdi\c'/H5. 4 tr//<7»a/acm/a/a), a natural sport of the ordinary hazelnut (B). 8 PLANT-BREEDING neighboring types. Such differences must be assumed to be produced each by a single mutation. By tliis means the significance of the mutations may best be judged, and whenever species dift'er from their nearest alUes in a higher degree, the inference is allowed that they have been origin- ated by more than one mutation. Since the pubhcation of Darwin's theory, the probabil- ity of such sudden changes playing an important part in the evolution of species has always found some support. Of late, the evidence has increased in this direction, especially under the influence of Cope. Discontinuous evolution has been defended among pakeontologists by Dollo, among zoolo- gists by Bateson, and among botanists by Korshinsky. This Russian author compiled the history of a large number of varieties from the widely scattered horticultural literature and showed that, in almost all cases where the history of the origin of a variety was recorded, it originated suddenly. Alany other varieties, especially among trees and shrubs, have been discovered, as such in the field, and, although their origin is not historically known, the constant absence of intermechates pleads vigorously for the explanation of their differential rjuahties by mutation. The conception of mutations agrees with the old view of the constancy of species. Tliis theory assumes that a species has its birth, its lifetime, and its death, even as an individual, and that throughout its life it remains one and the same. Thus it is only natural that wild species are almost always observed to be constant, since by a mutation they do not change themselves but simply produce a new type. This is allied to its ancestor as a branch is to a tree, the stem continuing its own growth, no matter how many branches it produces. Just so a species may produce quite a number of new forms without being changed itself, in the the least, thereby. Among palasontologists Scott has gi^'en EVOLUTION AND MUTATION 9 forth this same view. According to his conception, species are derived from one another by small shocks. Each shock caused the old hmits to be transgressed; but, after it, the new species remained unchanged until, perhaps after centuries, a new shock made it transgress its new Hmits. Each single type (be it species, subspecies, or variety) is thus wholly constant from its first appearance and until the time it disappears, either after, or without, the production of daughter species. On the ground of the mutation theory, there is a struggle for life among species as well as among individuals. There is selection, also, between competing species and among the incUviduals of the same species; the fittest will survive, — but tliis holds good for species as well as for individuals. As to individuals, natural selection may, to some extent, cause a divergence from the average type. But among species, natural selection is the most potent factor, since it eliminates some and therel)y protects and favors others. Thus we come to the conclusion that natural selection is as active as Darwin assumed it to be, and is as pre-eminent a factor in the process of evolution. It causes the survival of the fittest; but it is not the survival of the fittest individ- uals, but that of the fittest species, by wliich it guides the development of the animal and vegetable kingdoms. Resuming the main point of this discussion, we may sketch the origin of species, according to the theory of mu- tation, in the following manner. Species are derived from other species by means of sudden small changes which, in some instances, may be scarcely perceptible to the inexper- ienced eye. From their first appearance they are uniform and constant, when propagated by seed; they are not con- nected with the parent species by intermediates and have no period of slow development before they reach the full display of their characters. They do not always arise, but lo PLANT-BREEDING only from time to time. A parent species may produce its offspring separately at intervals, or in larger numbers during distinct mutating periods. After this production, the old species is still the same as it was before, and it subsists in the midst of its children. New forms are produced by the old, either in one, or a few, or in numerous incUviduals; in the latter case, the chance of survival is evidently enhanced. Some young species will be better fitted for their life- conditions than others, and the struggle for life will induce a selection among them by which the fittest survive. Even as the new species are produced locally and as the effect of local causes, the struggle for life and natural selection decide concerning the survival according to the local con- ditions. These conditions thus have a twofold significance for the development of the pedigree of the main groups of plants and animals, but it is probable that they determine the hues of progress chiefiy by their selective activity. The main arguments in the discussion of the production of species by slow changes or by mutations were taken by Darwin from the experience of agricultural and horticul- tural breeders. Therefore it is desirable to inquire into their real significance. Do they support the one or the the other view? Darwin assumed that tliey gave proof of slow changes, and took his arguments mainly from the agri- cultural side. In horticulture, however, as we have seen in discussing Korshinsky's work, the prol)ability is on the other side. In my experiments on mutabihty I have shown that it is possible to repeat and control the origin of horti- cultural and analogous varieties under strict experimental precautions, and that the full proof may be given that they originate at once, and not by a slow process of changes. They may, in the first instance, appear with the full display of their average character, or only with a small indication of it as an extreme variant of its fluctuation, but in the latter EVOLUTION AND MUTATION ii case the average is often reached after one more genera- tion. I observed the origin of the peloric toadflax and of a double marigold, and produced, almost artiiicially, the twisted variety of a Dracocephalum. In the case of the toadflax, Linaria vulgaris peloria, the change came suddenly, and more or less unsuspectedly, after a culture of about eight years. The ordinary form produces, from time to time, some few five-spurred, regular or peloric flowers. At once an individual arose which had such flowers only. The next year the mutation was re- peated. The seeds of the mutated individuals reproduced the new variety almost exclusi^'ely, and each plant of it had peloric flowers only. No intermediates were observed, neither in the number of the spurs of the flower nor in the number of the peloric flowers on the plants. It was as sud- den a change as any horticultural sport, but its ancestry had been purely fertilized and carefull} recorded so as to leave no doubt concerning the real nature of the mutation. The double variety of the corn-marigold (Chr^'san- themum segetum) arose in my garden in a culture in which I was increasing the number of the ray-florets by contin- uous selection. During four years I had succeeded in in- creasing this number to about sixty on each head, starting from the cultivated variety, with an average of twenty-one. All the ray-florets, however, belonged to the outer rows of the heads, as in the original variety. At once a plant arose which produced some few ligulate florets in the midst of the disc. This indicated the production of a double race. When the seeds of this mutating individual were sown, the next year, they yielded a uniformly double group; and from this time the new variety remained constant. The Dracocephalum moldavicum is an annual garden- plant belonging to a genus in which Morren has described ^i Fig. 2. A. The toadflax (Lhiaria vulgaris). E, C. Its peloric variety. D. A jieloric flower on an ordinary specimen. s; 5.' 5 hj o ,?■ c [2 ri ■ p m ro n|| ^ ^^ K- o ^ c ^ D- ?s ^ -1 P ^ o '^ "^ 1^2 o S ? ■-n fC -1 ^ Ij en P- M Q p -; 9 3 'Jq" PS-S 13 14 PLANT-BREEDING some beautifully twisted specimens. I succeeded in procur- ing such a specimen in this species by cultivating a race of it during some few years, selecting the specimens which showed a marked tendency toward variation in the arrange- ment of their leaves. The twisting appeared at once, but the race has not been continued. AU these, and many other, experiments have been con- ducted under conditions which allowed of a close scientific study. They confirm the common experience of the horti- cultural breeder in stating the suddenness of the changes and thv immediate production of distinct races. They show us the way in which analogous changes may have occurred in nature, and make it probable that sudden changes are, at least, an important factor in the evolution of the vegetable kingdom. With agricultural crops my experiments ha\'e been too rare to give a definite result. The German breeders assumed, as a rule, that they produced their races at will and by a process of slow variability and repeated selection. It is mainly upon this conviction that Darwin has based his con- ception of an analogous slow improvement of species in nature. This (ierman method has, however, been STib- mitted to a severe criticism by Dr. Xilsson, the director of the Swedish agricultural experiment station at Svalof. His pedigree-cultures have shown that the idea of a slow accumulation of characters by repeated selection is due to incorrect observations and to the use of untrustv/orthv methods. According to his experiments, changes occur in agricultural plants as suddenly as in horticultural species; there is no essential difference between them in this respect. By these discoveries the main support of the theory of slow and gradual evolution is broken down, and the analogv between artificial and natural production of species comes to plead wholly for the theory of mutation. These new i6 PLANT-BREEDING facts will be dealt with in our next chapter, and it may be sufhcient, here, merely to have indicated them. The principle of mutation is conducive to the assump- tion of distinct units in the characters of plants and animals. Even as chemistry has reached its present high develop- ment chiellv through the assumption of atoms and mole- cules as definite units, the ([ualities of which would be meas- urable and could be expressed in figures, in the same way systematic botany and the allied comparative studies are in need of a basis for measurement and calculations. The determination of the degree of affinity now largely de])ends upon vague estimates and personal views; while, on the basis of the theory of mutations, the relationship is meas- ured by the numlx-r of the mutations which have made the forms under consideration different from their common ancestors. The mutations themselves have evidently oc- curred in ])revious times and cannot be counted now. Hut if it were })ossible to count their products, the characters, the same aim could be reached. The study of these unit-characters may be undertaken in three different ways: first, by the production of hybrids; secondly, by the investigation of associated characters; and in the third place, by the cUrect observation of mutations producing such units. In hybrids the characters of the par- ents may be combined in different ways, but the unit-charac- ters connot be spht or divided. This follows directly from their definition. Thus the different combinations may lead to the distinction of the constituents of the mixture. In my third chapter I shall deal with this question on the ground of the experiments of Luther Burbank. ^ They afford a suffi- cient source of evidence to discuss this question and are well deserving of a separate treatment. On the other hand, their methods and scientific results are the same as those of the European horticultural breeders, as described elsewhere. Fig. 5- Lamarck's Evening-primrose {Oenothera Lamarck- iana), a mutating species. 17 1 8 PLANT-BREEDING The association of characters is often called correlation. It may be an accidental or a normal coincidence of charac- ter-units. But more often the same simple character mani- fests itself in different parts of the organism (as, for instance, in the color of flowers, berries, seeds and fohage) and thereby affords a means of investigating it. Of late, such associa- tions have become of liigh importance, since selection may be guided by them. Especially, in the isolation of new var- ieties of cereals has tliis use proven very valuable. Our fourth chapter will deal with these questions. For the direct observation of the process of mutating, the evening primrose of Lamarck affords, at present, an un- equaled opportunity. It produces numerous mutants, and does so in every generation, and almost any sample of pure seed may be used for this study. This species was described by Lamarck, from specimens of the botanical garden at Paris, a century ago. It seems to have since been lost. It was re-introduced into European garden-culture, about the mid- dle of the last century, by a nurseryman in London, who received the seed, without name and in a mixed packet, cul- tivated and multiphed it and sold it to the leading firms on the continent. Ah the strains derived from this scource show the same phenomena of mutability, as far as my experi- ments go. \Vhere the species is growing in America in the wild condition, is not known, at present, and so it is impossible to decide whether it has acciuired the habit of mutating in that condition or upon its introduction into European culture. Twenty years ago, I found this species on a waste field near Hilversum, in Holland, where it had escaped from culti- vation and was rapidly multiplying itself. Here it had pro- duced two new and distinct varieties which, up to the present time, have not been collected or observed elsewhere. One of them had smooth leaves, lacking the bubbles of the ordi- nary form; it was a fine type with narrower leaves and petals, Fig. 6. Leaves of Lamarck's Evening-primrose (A), and of two of its mutants. B. Oen. lata. C. Ocn. scintillans. 19 20 PLANT-BREEDING the latter often becoming ovate instead of cordate. The other had very short styles, the stigma reaching only to the mouth of the flower-tube, instead of being Hfted up above the anthers. Its ovary is only partly inferior, and it ripens only very few seeds in its capsules, wliich remain small. It has, moreover, some associated characters in its foUage by which it may be recognized before the flowering-period. In my cultures, both these varieties were found to be constant and pure from seed. Some further mutations ha^•e been produced on the same field, but since they were also produced in my experiment-garden, I shall not here mention them separately. In the year 1886, I collected some seed from the normal plants of this field and sowed them in my garden the next spring. This culture at once gave a new mutation wholly unobserved until that time. Three individuals diverged from the average, and all three in the same way. They con- stituted a new type which has been called OEnothera lata or the broad-leaved evening primrose. Its leaves have rounded tips, its stems are weak and bencUng and scarcely reach half the size of those of Lamarck 's primrose. It has thick flower- buds and produces flowers the petals of which often cannot completely flatten themselves. The anthers are barren of pollen, dry and twisted. Its ovary, however, is normal and can easily be fertiUzed by the pollen of the parent species. In doing so the next generation is, of course, of hybrid origin, but it does not produce intermediates but consists of some typical CEnothera lata and some normal Qlnotheni Lamarck- iana. By repeating the cross the lata type maybe kept indefi- nitely, occurring in about the same numerical proportion in each generation. Starting from these mutations, I began a regular scientiflc pedigree culture of Lamarck's evening primrose, fertilizing the flowers artificially with their own pollen, protecting them Fig. 7. IMutants of the Evening-primrose. A. The red-veined form (O. riibrinervis), which is of the same size as the original species. B and C. The dwarfish variety {Oen. nuuella). 22 PLANT-BREEDING from the visits of insects by paper bags and sowing, each year, the seeds of some few normal individuals of the race Tliis pedigree embraces, now, about a dozen generations, the first few of which were biennial, but the later annual. From tliis stock of normal plants it has regularly repeated its first mutation, producing some latas in almost every genera- tion. The number of these mutants was, on the average, about i^ per cent, the mutants themselves being always alike. Moreover, my pedigree culture has produced quite a number of other mutants. The most frec|uent among them is a dwarfish variety, the first flowers of which open when the stem is only some few inches high. It is called CEnothcra nanella and occurs as frecpiently as the CEnothera lata. It is completely fertile and produces an abundance of seeds, all of which give the same dwarf type, without ever reverting to the high stature of tlie parent species. I have cultivated these dwarfs during five, and more, generations and have found them true to their type. The first generations of my pecHgree culture had to meet with all the difficulties of a new experiment with unknown and partly unsuspected results. Accordingly, they yielded only a small number of mutants. i\s soon as the method had been elaborated, this number rapidly increased. In the si)ring of 1895 I sowed seed enough to have about 14,000 young seedUng plants, which T cultivated until they clearly showed whether they would mutate or not. The mutating indiAiduals were than isolated and grown under very favor- able conditions, but of the normal plants the larger part were destroyed. All in all, I isolated 60 dwarfs and 73 lata and five wholly different new types. Two of them were rare, one having been found only in one (O. gigas)and the other in two individuals (O. leptocarpa). Two others were less rare, the rubrinervis appearing in eight, and the albida in fifteen speci- mens. The fifth was the most frequent of them all, spring nJ my -^ ^^' '^^ts ^r^ Jgr^ gh^tf^^ .'/ dBs ' JK '^^M l^pHBfPt^ * ii i^.< n i^^^T ^Ji^^^SM Fig. 8. A flowerspike of the giant mutant {^Oenothera gigas), which origi- nated in my garden, 1896, 23 24 PLANT-BREEDING ing from the main stem of the Lamarckiana in 176 of the 14,000 seedlings. It was called oblonga. All these forms were purely self-fertilized and yielded uniform races without reversion to the original evening primrose of Lamarck. With the exception of the gigas, which has not been re- peated in this pedigree, all the types spring more or less regu- larly, in every generation, from the pure parent stock. As often as they were purely fertihzed they produced constant strains, which, however, did not differ from the previous races of the same name. Besides these, cjuite a number of minor mutations have occurred in my cultures. Some of them died in early youth or before flowering; others were barren of pollen, or not capable of fertilization, and yielded no seeds. Some were too weak for the conditions of my garden and succumbed, sooner or later, mostly during the winter after their germination. The range of mutability of this primrose, evidently, has not been exhausted; and even during last summer a wholly new type made its appearance. A main point in these observations is that the mutations occur suddenly, without preparation and witliout interme- diates. Xotliing indicates on the normal i)lants what their seeds will produce, and there is even no means at all by which to decide beforehand whether the fruit of one individual, or one branch, will Ijc richer than any other in the production of mutations or of some distinct mutant. The distribution of mutating seeds seems to depend simply upon chance. Nor are there intermediates. Each mutant is as good a repre- sentative of its type as its progeny will be; it does not need any special cultivation or improvement to reach the full dis- play of its character. No half-mutants are seen, neither from seed of the parent form nor from seed of the first mu- tant itself. These sharp distinctions clearly indicate that each mutation consists of the production of a single unit- nonimr library N. C. State College 25 26 PLANT-BREEDING character; because, if the characters were compound, they would spHt, from time to time, and be divided into their con- stituents. By this means a method is given of studying the expressions which the same unit-character may assume in the different organs of a plant. But this point will be more closely studied in another chapter. The question now arises, whether it must be supposed that species in nature ordinarily originate in the same way as in the case of the evening primroses. Of course, the de- tails of the process will be different in different cases. The number of the new types and the frecpiency of the mutating individuals in each will differ; sometimes they may, perhaps, be more rare and, in other instances, more crowded. Other differences there will, also, be. The main point is, knvever, that mutations occur suddenly and by leaps. One genera- tion is sufficien.t to produce the whole new type. This is a manifest contrast with the prevailing conception of slow and almost invisible changes pnxkicing new species. It may shorten tlie geological time recpiired for the evolution of the whole living world and bring it witliin the Umits derived from physical and astronomical evidence. Thus the theory of mutation satisfies these demands. The cases observed in horticulture, the constancy of wild species, the behavior of characters in crosses, the occurrence of shar])l}' defined small species within the ordinar}- species of wild plants and even of agricultural crops, and many other groups of facts, lead to the same conclusion. On the other hand, the slow change of one species into another has not, as yet, been })roven in any distinct and clear case. Therefore, we may assume that the mass of the present evidence points to the conclusion that species originate laterally from other species, by sudden leaps. These leaps we call mutations. Fig. lo Dr. Hjalmar Nilsson, Director of the Swedish Agricultural Ex- periment Station at Svalof. 28 11. THE DISCOVERY OF THE ELEMENTARY SPECIES OF AGRICULTURAL PLANTS BY HJALMAR NILSSON. A. DIFFERENT PRINCIPLES IN THE BREEDING OF CEREALS. From the beginning of civilization, the cereals have taken a prominent place in human culture. No industry has been so intimately connected with the interests of mankind, and upon no other agricultural crop has progress been so largely dependent. Long before the time of the ancient Egyptian kings, of the Romans and of the lake-dwellings of central Europe, the cereals yielded the principal nourishment in all the countries of the world where civilization developed itself. Solms-Laubach has pointed out that China and Egypt have cultivated mainly the same species and sub-species of grains, and that on this ground it must be conceded that their cul- tures have had a common starting-point. Three or four thousand years before Christ, the principal varieties must have been known to mankind, and it may even be assumed that the very first beginning of this culture is much older. Its probable origin is the central part of Asia, since only this region can have been its common source for the Chinese and Egyptians. Having so deep a significance, the cereals must have been given more attention and more care than any other crop. According to some verses of Mrgil, the Romans knew their cultivated races to be far from pure and uniform. They also knew that care had to be taken in the harvesting of the grains destined for sowing, since otherwise the races would surely deteriorate. Each year the best ears had to be selected in order to keep the varieties pure from an overwhelming 30 PLANT-BREEDING Fig. XI. Poland wheat {Triticum polonicum) . increase of the unavoidable admix- tures of little worth. During the middle ages no records seem to have been made as to the methods of cultivating cereals. Wheat and barley had been the grains of the ancients; to these, oats have been added during the period of the lake- dwellings, and rye is the most recent of the European species, having been introduced into Europe during the middle ages. Corn, of course, is of American origin, and has been con- nected with the development of the ancient American cultures, quite in the same way as the grains were con- nected with those of the old world. The idea of improving these valu- abk' crops seems to have presented itself only after the beginning of the last century. Different principles were set forth, as soon as the possi- biht}' of improvement had once been ascertained. Some of them were of a more practical nature, resting on direct observation, but others relied on theoretical views concerning the influence of environment on the (|ual- ities of Uving organisms. Both of these main directions have attained a high degree of significance in agri- cultural practice as well as in the purely scientific discussions concern- ing the origin of species in nature. NILSSON'S DISCOVERY 31 English breeders have, as a rule, preferred the more practical line of worlving, but their results have been isolated, and have not been combined into a dctmite system. German breeders, on the other hand, liave followed the theoretical principle of slow amelioration, and have developed this idea into a broad system, which has been applied by several of their most prominent men to the improvement of numerous varieties. Darwin, as is generally known, chose the principle of slow and gradual changes as affording the most reUable facts for his discussion of the manner in which species are produced in nature. In doing so, he has brought the Ger- man method to the rank of a scientific principle and secured for it the interest of the students of biology at large, but has almost thrown into obHvion the other side of the question. Of late, however, new facts have been discovered, which are of a nature to change the whole aspect of this part of the science of evolution. At the Agricultural Experiment Station of Sweden, at Svalof, the German method has been extensively tested, and the result has not been favorable to it. New discoveries have been made which go to prove that the whole principle of gradual changes rests on an insufficient knowledge of the laws of variability of agricultural plants, and may be replaced by more simple and more direct methods as soon as these laws are exactly studied. It is my object to give a survey of the deep significance of these Svalof experi- ments, partly in their practical bearing on agricultural plant breeding, but mainly in their complete compliance with the doctrine of elementary species, and in their appreciation of these as the true material from which selection has to make its choice. I shall endeavor to point out that these new dis- coveries must deprive the principle of gradual ameliorations of its present high rank in agricultural practice, as well as of its significance as a support for the prevaiHng views con- cerning the origin of species in nature. 32 PLANT-BREEDING Before doing so, however, an historical sketch of the principal methods and achievements of the most renowned breeders of cereals may be given. It will facihtate our •' i I s| 'wMl: j^ mi \'\vmml/' ■'/ F^H m WKiiil s ^ '^w\ 9 ^^ )Mjh w "J m i "i V '; I '. f j A :b. \ \ c 1 1 Fig. 1 2. A. Bellevue de Talavera-wheat, isolated by Le Couteur. B. Bearded white wheat, produced bv Patrick Shirreff. C. Squarehead wheat, the most famous production of the same breeder. appreciation of the most essential features of the wonder- ful variabihty of these plants, and will prepare us for an unprejudiced judgment of the opposite views concerning the NILSSON'S DISCOVERY ^t, significance of different kinds of variations for breeding experiments and for scientific discussions. — ^ Tlie first to discover tlie principle of improving cereals by selection was the English breeder, Le Couteur. He Uved in the first part of the last century on Jersey, one of the islands in the Channel, off the coast of France. Once he was visited by Professor La Gasca of the University of Madrid, who, far from admiring the purity and uniformity of liis host's cultures, pointed out to him how, in reality, they consisted of a mixture of more or less easily recognizable types. He suggested the idea that these types might have a chlTerent share in the harvest of the whole field, some of them being probably more and others less productive than the average. _In^ a field of wheat, he succeeded in distin- guishing23_forms, and in other cultures similar indica- tions of variabihty were observed. After Ms departure, Le Couteur saved the ears of the indicated types separately, and sowed their grains in small field plots in order to com- pare their productivity.l~He does not seem to have had any theoretical view concerning the causes or the nature of the observed differences, but simply assumed that the progeny of his selected plants would be Hke the parents.",' On this point he soon found himself justified by the results of his experiments. He had produced a group of new types of which some proved better and others less valuable than the ordinary sorts of liis fields. The best new varieties, isolated in this way, he then multiplied, and afterwards put them upon the market. One of them is still grown in England and the northern parts of France on a tolerably large scale. It is a kind of wheat called "Bellevue de Talavera" and it is known to be a very pure and uniform type. It is so uniform that it does not afford any deviations by which it can be subjected to further selection, and all trials in this direction have been in vain. Many breeders of later times 34 PLANT-BREEDINC; have approached this high degree of invariability in the pro- ducts of Le Couteur's selection, and only at present is it recognized as an instance of one of the most common laws, which rule the phenomena involved. Another celebrated breeder who worked on the same principle, though after a somewhat different method, was the Scottish agriculturist, Patrick Shirreff. He lived in about the middle of the nineteenth centiu^y and had his farm at Haddington in Haddingtonshire. During the first period of his work, he had no iK'tter conception concerning the purity of his fields than his contemporaries. But he observed that, from time to time, and as he thought by mere accident, a plant occurred which seemed far more promis- ing than all the remainder of the same field. Such individ- uals he marked, helping their development by pulling out their neighbors if they were crowded and surrounded them by all manner of attention. Then he saved their seeds separately and sowed them, in order to multiply Ms new types as fast as possible. That such isolated_indivi duals would yield a uniform progeny and become the ancestors of constant races he took for granted, and it is very curious to note in his writings that he did not judge it worth while to discuss this point, or to state the fact as he observed it. His races wTre pure, and there was no single reason for him to suggest that it could have been otherwise. Shirreff's exceptional plants were very rare, so rare even that in the first period of nearly forty years, he succeeded in isolating only four new varieties of prominent value. His first discovery was made in the year 1819. He observed a plant of wheat which surpassed its neighbors by its high degree of branching. It yielded 63 ears with about 2500 kernels. He saved the seeds, sowed them on a separate field and at considerable distances apart so as to induce in all the plants the same rich branching. He contrived to NILSSON'S DISCOVERY 35 multiply it so rapidly that it took only two generations to get seed enough to bring it advantageously into the trade. He gave it the name of Mungoswell's wheat, and it soon be- came one of the most profitable varieties of Scotland. It has found its way into England and into France, where it is still considered one of the best sorts of wheat. It is interesting to note that Shirreff had no idea of the necessity or even of the usefulness of a repeated selection. On this point he wholly agreed with Le Couteur. Without exercising any choice, he sowed all the grains of Ms selected plants and of their progeny, liis only aim being to multiply the new form as quickly as possible. They yielded a uni- form race, and were simply expected to do so. Only five years after his first selection, another excep- tional plant caught his eye. It was an exceedingly tall individual in one of his fields of oats. He saved and sowTd its seeds separately as in the previous case and won a variety which has since been largely cultivated under the name of Hopetown oats. His remaining varieties were the Hope- town wheat, found in 1832, which was discovered and multipUed in quite the same way, and the Shirrefl" oats, concerning the origin and treatment of which he has not judged it worth while to give any indications. Both of them have gained a high reputation and a widespread culture in Scotland as well as in some other European countries. Until the year 1856, these four varieties were his only im- provements. At that time, however, he had acquired more experience concerning the variabihty of his cereals, and he resolved to profit thereby. He had observed that though exceptionally promising plants arc of course very rare, less promising individuals may be met with in larger numbers. They would not yield such excellent races as the four men- tioned above, but notwithstanding that, they might sulfi- 36 PLANT-BREEDING cicntly surpass the average to be advantageously selected and cultivated. The trials would have to be made on a larger scale, and the results would be less striking, but on the other hand, improvements could be brought about in a far lesser number of years. Or, to state it more correctly, the results w^ould no longer be dependent on rare and casual discoveries, but would be brought about systematically. He began his selections, after this new method, with wheat, and saved 70 ears from different individuals. All of them seemed to promise more than the average varieties of his fields. Of course the kernels were sown separately for each mother plant, and their progeny was accurately tested and compared. As previously, he took it for granted that all of these new strains would be constant and uniform; he observed the fact but did not judge it interesting enough to mention it specially. Among liis 70 strains he chose at the end the three best ones, multipUed them as fast as pos- sible in order to bring them into the trade, and rejected all the others. Those three received the names of Shireff's Bearded Red Wheat, Shirreff' s Bearded White Wheat, and Pringle's Wheat. For many years they have had a notable place among the best local varieties, and the white variety among them has even found its way into England and France. Having obtained these results with wheat, he started, in the year of 1862, a similar experiment with oats. Four of his selections proved to excel the common sorts and were introduced into the trade. They bear the names of Early Fellow, Fine Fellow, Long Fellow, and Early Angus. Like the wheats, they have been constant and uniform from the very beginning. Ten years afterward, Shirreff published an account of his results and of his methods. It was a httle book, printed only for private distribution. But it has been translated NILSSON'S DISCOVERY 37 into German by Dr. Hcssc for the use of the general public. It is largely devoted to the description of the superior qual- ities of his varieties, and the historical evidence concerning their origin is only incidentally given. From his statements, we may gather that at first he assumed his mother plants to be sports, but afterwards took them to be simply old con- stituents of the ordinary cultivated varieties. He observed these to be mixtures, consisting of more and of less abun- dantly yielding types, and on this observation founded the method which he followed during the latter part of his life. He satisfied himself that even within these mixtures the constituents were uniform and constant races, and there- fore it was only natural that after isolation they would re- main so. Shirreff seems not to have had any idea of the possibiHty of the existence of another form of variability as a starting point for further improvement. Considering the great importance which has been conceded in Germany to this possibility, even during the latter part of Shirreff's life, it is not without interest to lay some stress on this fact. The more so, since he had in mind the desirabiUty of other ways to reach the same purpose more surely and more quickly. He turned himself to hybricUzations and made some valuable experiments on the crossing of cereals, and from his statements it seems ({uite evident that he did so only in the firm conviction of having exhausted the possibili- ties offered him by variabihty alone. Le Couteur and Patrick Shirreff seem to be the only breeders of cereals who ha\e worked on the principle of one single initial selection and of subsequent rapid multiplica- tion without renewal of the choice and without isolating the best individuals during the following generations. On this point they are to be considered the precursors of the method which has of late been discovered anew, at Svalof. But they had only a very limited appreciation of the importance 38 PLANT-BREEDING and productiveness of the principle involved in their method of selection. At nearly the same time with the latter experiments of Shirreff, another renowned breeder began to improve cereals by selection. At Brighton, in one of the southern districts of England, F. F. Hallett began his wT^rk in the year 1857. He seems to have known the improved varieties of Le Couteur but not those of Shirreff. He started from r^uitc another point of view, which did not rest upon the observation of the ^'ariability of his grains, but was derived from his previ- ous experience in tlie 1:) reeding of cattle, especially in that of the short- horns. His principle was that each plant has one head which is the best of all its ears, and that in the same way each ear has one best kernel. Moreover, he was convinced that the best kernel of the whole plant is always to be found in the best ear. He also assumes that the qualities of the single kernels arc inherited \)y the plants wiiich they produce. From these premises he concluded that varieties could be improved by choosing the best kernel of the best ear for their reproduction. This choice had to be repeated through a series of generations, but his experience taught him that though the gain was large in the beginning, it did not con- tinue so, but soon reached a limit which it was practically impossible to transgress. Two other features distinguished his work from that of Le Couteur and Shirreff. In the first place, he tried to improve his plants directly. He satisfied himself that a plant, in order to attain its utmost development, must have ample food at all seasons, and that for this purpose not only manure but also depth of soil and space were essential. Therefore he planted his selected plants in a little garden near his house, gave them the best garden soil and the ordinary culture and treatment of garden plants. By this Fip;. 13. A. Hallett's pedigree Chevalier barley. B. Hal- Ictt's pedigree wheat. 39 40 PLANT-BREEDING means he increased the number of their culms and heads and the number of the spikelets and kernels in the individual ears. Twenty to lifty and more ears on a plant of wheat HALLETT'S NURSERY (PEDIGREEl WHEAT, Bred" upon lljo same princfple of REPEATED , races of Aalmals. STARTINi; FROM IINE l.ri\l\ 1> l_\ni Y SclccUoD which has produced our pure II mm i'kaiis sictt:s,siVKi.v ONE OF THE ORIGINAL TWO EAKS. m HOW OITR WHEAT CROPS MAY BE DOUBU3>. Fig. 14. A reproduction of part of the first advertisement of pedigree wheat by F. F. Hallctt. Sec the Times, London, June iS, Nov. 8, and Dec. 19, 1862. became the rule, and ears with less than 80-100 kernels were commonly rejected. Tliis large increase can in some sense be called artificial. It appears as a direct result of the change of culture and therefore came wholly or almost wholly during the very first year of the selection experiment. NILSSON'S DISCOVERY 41 Of course the influence of better nourishment can only attain its liighest degree in the lapse of some generations, since only the very best nourished kernels will yield the very richest plants. In some cases, this process of artificial amehoration will be rapid, but in others more or less slow. Some instances may be given. Hallett's "Original Red Wheat" was started from an ear containing 47 kernels. The next generation yielded an ear of 79 grains, and the second came up to go in the richest car. During the seven- teen following generations, this limit has practically not been exceeded, the richest ear during all that time having produced only 91 kernels. In other cases the development was equal- ly rapid in the beginning, but lasted during a longer period. The Hunter's Wheat began with 60, increased in the first year to 90, and then during some twelve years came up to 106 in the best ear. The Victoria Wheat began with 53 and slowly increased to loi, the gain of the first generation being only seven kernels for the best ear. Hallett assumed that by this treatment the hereditary qualities were aiiected in the same way as the visible characteristics, or in other words, that the varieties were directly improved by the cul- ture, the selection having only the purpose of fixing the acquired qualities. A second feature of Hallett's method was the great care bestowed by him on the comparison and testing of his plants. For each single individual, the heads were counted and the exact number of kernels in each ear traced. These figures were considered as the main qualities according to which the plants were judged, and on this ground the average specimens and those of minor worth could be eUminated. The prominent ones were then brought to his study and minutely compared in all their visible marks. In this way the very best specimen was isolated, and the same work begun for its culms and ears. Only one ear was ultimately 42 PLANT-BREEDING chosen for the sowing of the next generation, and this was the best on account of its having not only the largest number of kernels, but also the biggest and best formed ones of them all. Repeatedly Hallett has insisted upon the immense amount of work which this kind of selection yearly recjuired. This is the more curious since at the present time hardly anybody attributes much importance to a choice of the best seeds on a given individual, jjrovided only that small or un- healthy kernels arc sufficiently excluded. For Hallett, on the contrary, the choice of the one best kernel on the wliole plant was the real aim in his selection. He tried all means for comparing the indivichial kernels of his one superior ear with one another and for linding out the best one. He made investigations embracing, on one side, their x'isiljle marks, and on the other their ]>l:ices on the ear, those in the middle part being in the main the better ones. But he could not discover distinct laws and so had to give up the whole system. Leaving aside all comparison of the kernels of liis chosen head, he resolved to sow them all and to delay tlieir study until the next generation. In this he repeated his testing in the manner described and judging the kernels from the pkints they had produced, he was enabled to discern among them the one 1)y means of which he wished to continue his race. To this method of selecting each year the best kernel on the best ear of the best ])lant, Hallett has given the name of pedigree-culture. Its essential feature is the repeated selection. Some of his varieties were given to the trade under the names of pedigree wheats and ])edigree oats. Of the latter, his "pedigree white Canadian oats" and his "pedigree black Tartarian oats" may here be mentioned. Both were introduced in the year 1862. He claimed that his gradual amelioration gave better varieties than the princi- ple of the isolation of single plants. This may be seen by NILSSON'S DISCOVERY 43 the title of the address dehvered by him in London in 1862, in which he first pubhshed his resuhs and his views. It was entitled, "On pedigree in wheat as a means of increas- ing crop." The improvement was obtained by the increase of the size of the ears, their numlx'r of kernels and the size of the latter. The number of heads on a plant he did not con- sider as a subject of selection, but rather assumed that it was wholly determined l3y the relative distance between the plants and therefore by the space given them in sowing. For him, the productiveness of a field was proportional to the yield of the single ears. Moreover, he assumed that his pedigree-races were not only to be amehorated but must be kept up to their highest point of development by continued selection. As soon as selection ceased, they would return to their original starting point, and their su])eriority over the ordinary cultivated varieties would chsappear. This assertion has a distinct and deep significance in agricultural practice, and has gained a great deal of influence in the discussion of theoret- ical questions as well. For practice it means that all the seed destined for sowing should be produced directly from the pedigree-stock, and that this is to be kept constantly under the same conditions of treatment and sharp selection. The truth of this assertion has been accepted by his custo- mers, and this fact has left the production of seed grain almost entirely in his hands. It is easy to see that the gain made by the breeder of a new variety depends, for a large part, on the acceptance of this proposition. In the varieties produced by Le Couteur and Shirreff, all seed is of equal value, provided the races are kept pure and free from admix- ture. Any one may multi|)ly them with the same success as the original breeder, but on Hallett's principle all the profit of the production of rehable seed grain was given into the hands of him who kept the original pedigree. 44 PLANT BREEDING I need not now discuss the truth of this assertion, since the same principle has been accepted by the German breeders. 1 might, however, point out that the real difference between Hallett's method and that of his two previously mentioned countrymen is to be sought in the choice of the starting points of their experiments. Le Couteur and ShirrelT have expressed themselves clearly on this point. "With them, all depends upon the first choice. What remains to be done afterward, is only the multiphcation of the progeny of the chosen plant. Hallett, on the other hand, is silent on this most essential question. Like them, he started, in each single case, from one plant, and therefore must have made a choice among the ty])es which his fields afforded him. On Shirreff's concei)tion, this clioice must have been the decisive jjoint in Hallett's work, and not the subscfjuent selection, and that this is true may be proven by his arguments. In the first place, Hallett has brought into the trade new and distinct varieties, and not merely more ])roduclive strains of the ordi- nary sorts. This may be seen by ihe names of the forms already cited, and to which the very distinctive types of his (jolden Drop wheat and Chevalier l)arley may be added. ]\Ioreover, it is proven by the fact that his varieties have kept their place in agriculture at large and are still keep- ing it, although it is a long time since Hallett himself dis- continued their pedigree-culture. They are now known to be independent varieties like those of Le Couteur and Shirreff. A second argument is given in the fact that the \alue of Hallett's varieties is dependent on his first choice, and that if this should prove a mistake, no subsequent selection is adequate to amend it. The proof of this is given by the miscarrying of some of his pedigree-cultures. Of course, most of these cases he will hardlv have mentioned, but it is NILSSON'S DISCOVERY 45 a well-known fact that his "Original Red Wheat" after- ward proved to be a failure. A very remarkable principle has been introduced of late into the methods of improving cereals by two highly distin- guished breeders. Working independently of one another, they have come to the same idea, and the ameHorations they have brought about give proof of the correctnessof their views. At the agricultural experiment station of Minnesota, W. M. Hays has appUed it to the improvement of wheat, and in Germany on his farm at Petkus von Lochow has appUed it to the selection of rye. The idea is the judging of the hered- itary value of a plant, not by its own visible marks, but by the average value of its progeny. It must be granted that the visible qualities of a plant are only a very imper- fect basis of measurement of its fitness to reproduce these quahties in its progeny. The direct study of this progeny in itself must be a far more reUable guide in such an estimate. The new principle was of course combined with the choice of single parent plants as the starting points for new races, and in this important feature it compHes with the principles laid down by the two first English breeders whose methods I have discussed. But with them the first choice was the principal act, although Le Couteur as well as Shirreff in his second method have largely relied on the comparison of the progeny of their first selections and rejected all those that proved inferior to his expectations. In Minnesota, the most widely cultivated varieties of wheat were Fife and Blue Stem, and both were decidedly inferior to the ordinary spring wheat varieties of other states. However, they showed themselves to be as impure as any other ordinary sorts, and thereby yielded material for method- ical improvement. Hays chose from among them a con- siderable number of types, and after sowing the seed of these 46 PLANT-BREEDING single mother plants, he compared their yielding capacity in the next generation. In order to have an easy standard of comparison, he sowed a hundred kernels of each and thence derived the name ''centgener power" for the index of productiveness of the single races isolated in this way. IHe claims to have obtained varieties which, under the same culture and treatment, will yield lo to 15 per cent more than the old unpurified wheats of ^linnesota. The same principle of judging the ])arent jjlant Ijy the average value of its progeny, and of founding selection on this mark, has been applied by von Lochow to rye, and it is said that his new race of "Rye of Petkus" as it is called, excels all the f)lder improved German kinds of rye, and that even the celebrated rye of Schlanstcdt may soon prove to be surpassed by it. We have gi\en a sur\ey of the most ])rominent and most renowned principles in the breecUng of cereals, and liave only to complete our hst by a description of the method followed by the larger number of the breeders of Germany. Among them, Heine, Drechsler, ^Mokry and Rimpau may here be named. Their purpose was to improve the ordinary varieties by continuous selection, directed according to distinct \'iews and requirements. They considered the starting points of the English breeders as accidental sports which no doul^t might be made use of with advantage, but would only yield improvements of an inferior rank. Two features are essential to this German method. First the initial choice, and secondly the slow and gradual improvement by selection. In this first choice they did not try to obtain deviating types and to isolate them from among the throng. Quite on the contrary, they selected the best representatives of the variety they wished to improve, in order to be sure to retain all of its good features in the new race and to combine them with the new characters which NILSSON'S DISCOVERY 47 they thought it possible to give them. Starting from this point of view, it was essential not to begin with one single mother plant, for tliis might perhaps possess, among those qualities wliich necessarily or at least ordinarily escape obser- vation, some inferior ones, whichj it must be feared, might destroy the whole effect of the ameUorations obtained on other points. Dependence on soil and manure, resistance to disease and other essential ([uaHties are not so easily taken into consideration when the selection is performed only at the time of the harvest, as was then the custom. In order to become as independent of these as possible, the only way seemed to start with quite a considerable number of indi- viduals and to rely on the laws of chance, trusting that these would keep all qualities in their average state, except those which should be consciously subjected to selection. It was this group of incUviduals that was to be amehorated. A scheme of the desired improvements was made, and each year those ears or panicles were selected wliich more fully comphed with it than the remainder. The result was a slow progress, but it was thought to be more rehable than the sudden amehoration of the EngUsh breeders. Moreover, sudden improvements are, os a matter of fact, Hmited in their degree, and even the pedigree-cultures of Hallett did not escape from this objection. The German principle w^as assumed to be unhmited, progress along the prescribed lines seeming to be always possible. As pointed out in the beginning, Darwin has, in large part, founded his theory of the slow and gradual change by which the species of plants and animals are transformed into one another, on the views of the German breeders of his time. For tliis reason we shall have to subject their principles to an elaborate criticism and the short indication given may therefore be sufficient for our present purpose. The most general conclusion to which our historical 48 PLANT-BREEDING sketch has led us is obviously that by very dilTcrent methods and under the intluencc of widely divergent theoretical premises, eciually good improvements have been obtained. We may add that even in the number of new and useful varieties produced, no single one among these methods evi- dently excels the others. It is always a small number, not exceeding ten or perhaps twenty novelties in each single instance, and orcUnarily even far less. Thus all these princi- ples are seen to have only a hmited apphcation, and perhaps failures have been more numerous than successes althoufrh as a rule only the latter have been recorded. Hence we may conclude that our knowledge of the variability of cereals is not yet sufficient to enable us to exhaust all of its possibiU- ties, or at least that such a knowledge was not in the posses- sion of the breeders whose great achievements have given the material for our present sketch. B. THE SWEDISH AGRICULTURAL EXPERIMENT STATION AT SVALOF. During the last twenty years, experiments in the Ijreed- ing of cereals and other agricultural crops have been con- ducted on an unusually large scale at the Swedish experiment station of Svalof. Considered from a practical point of view, they ha^■e produced cjuite an astonishing numljer of new races, by which agriculture in almost all the districts of Sweden has been greatly improved, and which are now at- tracting the attention of numerous agriculturists in other countries. Their methods took their origin from those fol- lowed in Germany, but were soon changed, and may, at present, be more closely compared with the work of Le Cou- teur and Shirreff, though developed quite independently of these men, whose ideas were, at that time, only locally appreciated. For the students of the problems of evolution, the methods 49 50 PLANT-BREEDING and the results of the Svalof station have a very deep signifi- cance. They contirm the fact that the ordinary cultivated varieties of cereals are by no means pure, but must be con- sidered as mixtures of well defined types. Moreover, they show that these types are far more numerous than was pre- viously supposed, and include hundreds of forms within each of the now prevailing sorts. They also show that the differ- ences among these newly discovered elementary types arc far greater than might be suspected from the study of the varieties isolated by other breeders. The range of variabil- ity disclosed by these new studies is simply so wide that it affords all the re(|uired material for almost all the selections desirable at present, and will no doubt continue to be an inexhaustible source of im])rovements for a long succession of years. They are founded on the ])rinci])le of single selec- tions, and the range of appHcation of this method is pro\en to be so extensive as to make all ideas of repeated or con- tinuous selection simply superfluous. It is even so rich in its productiveness tliat there is scarcely any room left for other methods of improvement; and especially should all endeavors of winning ameHoratcd varieties of cereals by means of hyl)ridi/.ation simply be left out of consideration, as compared with the immense number of more easily pro- duced novelties which this method offers. Leaving the teachings which may be derived from this work in the study of the evolution of the organic world for another chapter, I shall now tr\- to give an idea of the work itself. This may be divided into two parts; the first com- prising the use and criticism of the German method, and the second embracing the discover}^ and application of the principle of selecting elementary species. Some historical details may precede this discussion. Svalof is a little village in the Swedish province of Schonen, situated in the neighborhood of Helsingborg, Lund and NILSSON'S DISCOVERY 51 Malmo, close to the southwestern shore, and opposite Co- penhagen in Denmark. In this village, a company for the production and improvement of seed-grains for the southern part of Sweden was organized in the year 1886. Its aim was the procuring and testing of new and foreign varieties of agricultural crops, in order to replace the Swedish sorts, which at that time were slowly but manifestly deteriorating. This deterioration was discovered to be a consequence of the multiplication of admixtures of less value, which, though rare and unobjectionable in the countries whence the vari- eties were derived, were seen to thrive in a most obnoxious way under the influence of the Swedish soil and climate, and to lessen the value of the harvest in an important degree. To procure new samples of seed grains was the first way of combating this evil, the second being the purifying of the introduced supplies before giving them into the hands of the Swedish farmers. This cleaning could be performed partly in the imported samples themselves, but had to be combined also with the culture and multiplication wliich usually precede the sale. The company was founded by private agriculturists and had consequently to serve only the needs of practice. All educational aims and purel}- scientific researches are ex- cluded from its program, but, on the other hand, its work is based on exact scientific methods. Its botanical studies are as broad as possible, but always in the direct service of agricultural practice. In this respect it is to be sharply con- trasted with most of the experiment stations of Europe and America, and it is important to state that exactly through this procedure the obtained results have come to be of ex- ceptionally great significance for science as well as for prac- tice. Another consequence of this essential feature of the program is that its publications are destined only for the farmers of Sweden. They are pubUshed in the Swedish 52 PLANT-BREEDING language and deal with tlic results (^f the work. Fortu- nately, however, the Director and his staff have, from time to time, given short surveys of the progress realized, and of the methods followed in securing these practical results. One of the means by which the young company contrived to gain a notable influence over Swedish agriculture, was by increasing the interest of the farmers in the purity and the control of their seed grains. Exhibitions and distribu- tions of samples of pure seeds, descriptions of the various marks by which the varieties may be recognized, repeated inspections of the fields of the station, where pure cultures were grown side by side with the common Swedish sorts, gradually convinced the farmers of the great significance attached to the careful choice of their sowing-seeds. As soon as this conviction Ijecame general, the results could no longer remain doubtful, and, gradually, the fame of the station increased to a degree corresponding with the aug- mentation of the harvest. This purification of the imported strains must evidently lead to an exact study of the constituents of the original mix- tures and to a comparison of the part they take in the harvest. In the beginning, however, these were wholly obscured by the views which were then prevalent in Germany concerning the improvement of races among agricultural plants. It was taken for granted that the ])urification of the imported samples was simply to make them true representatives of the variety under the name of which they had been bought, so as to guarantee their ([uaHty to the Swedish purchasers. Furthermore, it was desired to accHmatize the best foreign kinds and to make them suitable to the requirements of the soils and climates of Sweden as well as to the various de- mands of the local industries. This part of the program, however, was intended as an application of the German 53 54 PLANT-BREEDING methods of improvements to the special needs of Swedish agricuhure. From these statements it may easily be gathered that the importation of new and valuable kinds from neighboring countries was, at first, one of the chief occu})ations of the station. The most prominent and most renowned varieties of the cereals of Europe were purchased and tested, the old and common sorts as well as the newly introduced and ameli- orated kinds. After fmding them ade([uate to the local cir- cumstances, they were multipHed, exhibited and recommen- ded and hnally given to the trade. In this way, Prol)steier oats, Tigowo oats, S(|uarehead wheat, \'ictoria ]x>as and different kinds of barley have been distributed. By their culture, the agriculture of the southern parts of Sweden was noticeably improved, and even the export of grains to Bel- gium and other Kuro])ean coimtries, which previously had suffered much from the deterioration of the races, could be restored to its former degree of importance. The influence of these new methods may best be judged by the rapid growth of the company. Already in the second year, it could extend its interests, which were primarily in- tended for the southern part of Sweden only, to the whole countrv. Soon afterwards, another company was organ- ized on the same principles and with the same aims. It had its seat at Orebro and was destined to work for the middle part of Sweden. But after an existence of only four years, it was combined with the Svalof company, which then (1894) took its present name of Sveriges Utsadesforening, or Seed- grain Society for Sweden. It entered into relationship with the greater number of local agricultural companies and was financially aided by them as well as by the Swedish govern- ment, so as to be enabled to work on a largely increased scale. Gradually the combination of the experimental and the commercial sides of the work became too cumbersome, and NILSSON'S DISCOVERY 55 moreover brought about a kind of competition with the local seed dealers, which was felt to be a hindrance to its further development. Five years after its establishment (i8gi) these considerations led to a separation of the two branches, a separate company for the sale of the improved grains being organized under the name of Allmanna Svenska Utsadesak- tiebolaget or General Seed-grain Trading Company of Sweden. This company has its seat at Svalof, too, and re- ceives the seeds of the ameliorated varieties which the society has produced, in order to multiply and distribute them. It is operated constantly under the control of the seed-grain society and thereby is enabled to keep its races uniform and to sell them under a full guarantee of purity. Before leaving the history of the experiment station, some words should be added concerning its means of providing races for different parts of Sweden. Sweden embraces a wide range of climates, from its cold northern parts to the mild and favorable clime of the southern provinces. ^Moreover, there is a large variety of soils. Hence it is evident that the production of good cereals for all those various parts can- not be effected at one single point. No variety can claim to be appropriate for a definite soil or climate before it has been tested under the circumstances for which it is destined. The work of the society is therefore twofold, and the principle has been accepted that the varieties are produced at Svalof, but afterward sent to other localities, according to their qualities and their probability of success. Everywhere in the country, the numerous local agricultural societies are co-operating with the station of Svalof for tliis purpose. As soon as a new race is considered especially recommendable for some soil or some chmate, it is sent to the locaUty in question and tested there by field cultures in comparison with the local sorts. By this means, many valuable improvements of local cultures have been obtained. 56 PLANT-BREEDING With the same object in view, two branch stations have been organized. One of them is situated at Lkiina in middle Sweden, and the other at Alnarp in the same region but on a richer soiL At Uhuna, for instance, the cuUures of the new Svalof Black Bell oats are attracting special attention. During the first years of its existence, the station followed the methods of selection and amelioration which, at that time, were generally accepted by the breeders of central Eu- rope. As we have seen in our last lecture, the German breeders considered the im])urities of their races as of minor importance. They could ])v gotten rid of by a careful choice of the best and most typical ears, and the saving of seed for sowing had of course to be accompanied always by some such kind of selection. The exclusion of inferior ears was more or less considered as the necessary means of keeping the races true to tlu'ir standard ty])e. Improved races, as a rule, were more responsi^■e to soil, manure and treatment than the local varieties. It is, however, unavoidable that, with the straw of the manure, some stray grains of these inferior sorts will, from time to time, and not rarely, come onto the fields. Here they will be content with a lesser supply of food, space and care than the improved races, and thereby be enabled to grow faster and multiply more ciuickly. It is hardly conceivable how soon these inferior races may multiply themselves to such an extent as to occupy large parts of the field, supplanting the ameHorated type and lessening the harvest to a noticeable degree. In bad years, even the wind oats which scatter their small seeds to the winds and thereby yield nothing at all for the harvest, may be seen to replace more than half the stock of the fields Under such circumstances, keeping the races pure by means of selection is evidently a necessary part of all intelli- gent culture. It is the first thing to be done, but it is consid- ered hardly worthy the name of imi)rovement. In Ger- 57 58 PLANT-BREEDING many, real improvement was treated as a separate occupation and was considered as requiring a large amount of study, and the devoting of oneself to a proposed aim. The gener- al custom was to start such experiments from the best local or improved varieties by an initial choice of a certain number of typical heads. Such a group of selected plants was called the elite, and this elite had to be ameliorated accord- ing to the prevaiHng demands or even simply in accordance with some ideal model. Year after year, the best ears of the ehte group were chosen for the continuance of the strain or family, and slowly, but gradually, its quahties were seen to improve in the desired direction. After some years, such a family might become decidedly better than the variety from which it had been derived. Then its yearly harvest would be divided into two parts, after having been sufticiently purified ])y the rejection of accidental ears of minor worth. The best ears were carefully soiight out and laid aside for the continuance of the elite strain, but the remainder were sown on a distant field in order to be multipHed as fast as possible. By this means, after a multiplication during two or three generations, its product could be used as seed grain for the farm or sold to others for the same purpose. Each year the elite would, of course, give a new and better har- vest which could be multiphed and sold in the same manner. From tliis description, it may easily be gathered that an improved variety, produced after these principles, cannot be called a race in the ordinar}- sense of the word. Only the ehte itself is a pure race, but it consists of only a small family, cultivated on a single farm. The extensive cultures of the succeeding years, however, are not related to one an- other in the ordinary way of ancestors and descendants. They are, or at least they should be, the ends of succeeding side-branches of the elite, each branch being surpassed in excellence by its successor, and therefore no longer deserv- 59 6o PLANT-BREEDING ing to be kept in culture. Since only the elite can produce the most advanced side-branches, the production of seed grains has always to return to it or rather to be started anew from it. No farmer should sow his own harvest, because if he docs so, he will soon be surpassed by others. Or, if he should be able to do it without harm, it can last only for a few years, since he cannot keep up the selection which alone is ade([uate to maintain the race at its highest standard. Contrary to the opinion of Hallett, who claimed to pro- duce his ameUorations by giving his plants large space, ample manure and the best possible exposure and treat- ment, the German j^rinciple was to make the selections under precisely the same conditions as those of the ordinary field cultures. It was assumed that changes produced by the outward conditions of life, were only of a temporary and and not of an hereditary nature. Hereditary qualities were assumed to be innate and independent of environmental intluences. Only by means of selection could they be fixed, increased or lessened, and fmally changed in detinite ways. On the ground of these views, selection was the true factor of the improvement, and since the breeder could select ac- cording to his own wishes and ideals, it was believed that selection was a means of changing any plant in any direction, and to any desirable degree. By direct changes, brought about by local and individual differences in the life conditions, this selection could only be misled, since such a change might be taken for an hereditary improvement whenever its real cause was hidden. Therefore it was a rule to reject all specimens which could possibly have profited by an excep- tional amount of space, manure or Hght, before beginning the real selection. Such were the more or less clearly understood, and more or less generally accepted views in central Euro])e at the tjme of the estabhshment of the experiment station at Svalof. No NILSSON'S DISC(3VKRY 6i reason to doubt their validity was at hand, and moreover, the cvidenec was only seanty and widely scattered, without affording sufficient material of facts for a thorough criticism. The results of the English breeders were hardly accessible at that time, and so the Svalof experiments had to begin by following the German principle. Resuming the principal features, we may state that it commenced with the choice of a certain number of ears, and cultivated their progeny as a mixed family, in which, year after year, the best heads were chosen in adequate number for the continuance of the race. / The experiment station at Svalof has accepted the prin- ciple that the selection cultures must be made on the same soiljinjl under the same conditions as the ordinary field cul- tures. Especially, the distances at which the seeds were sown from each other had to l^e the same, this being a point which had often been dealt with in another way, since by a somewhat larger relative distance, the treatment and the final distinguishing of the single plants is notably facilitated. This principle has been found to be reliable, and has been kept unchanged through all the periods of experimentation, which have supplanted almost all others. Moreover, the methods of testing and comparing have been largely improved. Instead of the personal apprecia- tion of the c[ualities of the ears, accurate measurements have been adopted. An elaborate book-keeping reciuired the statement of a large number of c[ualities by short indica- tions, and figures came to be preferred to descriptions. The length of the ears was given, their form indicated by width and breadth, and by the place where both reached their max- imum value. The density could be measured by the num- ber of nodes and spikelets, and in the latter, the number of single kernels could be noted. Other valuable c|ualities recjuired separate tools and instruments, and even the degree of brittleness had to be expressed by figures. 62 PLANT-BREEDING By these means it was soon found possible to extend the experiments to a previously unknown number, and, at the same time, to obtain far larger deviations from the initial type in a relatively short succession of generations. There- by the breeder was enabled to collect his experience on a scale large enough to yield the material for a full experi- mental criticism of the whole method. The result of this part of the work pro\'ed, however, to be not at all satis- fying. Of course, the first selection experiments were conducted according to the local needs of the farmers. Among oats the celel^rated races of the Probstei were cultivated, among the peas the variety called Victoria, and among wheat the squarehead sorts. Shortly before, the French breeder, Vil- morin, had produced a new variety of oats to which he had given the name of Ligow^o oats. It was tested at Svalof, and its introduction into Swedish agriculture has l)een one of the l)est successes of tlie young station. In the same way, two of the older varieties of barley, the "Plumage" and the "Prentice," were recommended and soon largely distrib- uted. The testing was always performed under strict com- parison with the local varieties, of which, for this reason, a considerable number were kept in culture. In the meantime, the deficiencies of the method could not escape observation. All those which were of a purely tech- nical nature could be overcome, and on this side of the problem a high degree of perfection was attained. But there were other weak points which were related to the very foun- dation principles of the method. Among these, the principal one was that the continuous selection of the best specimens in an arbitrary direction did not lead to improvement in all cases. Quite on the contrary, success was rare; so rare, even, that it could almost be looked upon as an exception. The fact itself was not new, since in Germany, also, only NILSSON'S DISCOVERY 63 in exceptional cases a real improvement had been obtained. But, of course, usually only successful instances are pub- lished, and concerning the remainder ordinarily no evidence is at hand. In Svalof, however, where numerous experiments of the same kind, but with different varieties of cereals, were con- ducted side by side, the fact could not escape observation. Soon, the idea suggested itself that if success is an exception, the principle involved in the method can hardly be a valuable one, at least, not one on which the breeder may confidently rely. An instance may be given. As such, I choose the Chev- alier barley, which is one of the most ^'aluable kinds for the brewers. In Sweden, it has the defect of being often ex- posed to lodging or lying down. The culms are too weak, and are thrown down by wind and rain shortly before the time of the harvest. Great losses are usually the conse- quence, and it was considered a distinct necessity to breed a Chevalier barley with culms stiff enough to resist these evils, even on the hard soils of the middle parts of Sweden. Here the culture of this variety had been tried on a large scale, but wos given up in consequence of the defect alluded to. In order to introduce it anew, and to restore the brewer's industry to its former degree of development, the Chevalier barley had to be improved and adapted to the circumstances. This demand seemed the more proper, since elsewhere and especially in Germany, this barley had attained the height of its renown exactly at that time. There could not be any doubt that it was the best kind for brewing purposes. On this account, it was cultivated at Svalof on a large scale, and with all possible care. It was submitted to repeated selec- tion with the distinct purpose of giving it stiffer culms. The results, however, did not correspond with the expectations. The harvest remained comparatively small, and the quality 64 PLANT-BREEDING was not that which might be expected. The cuUiires were correspondingly increased in extent, and the selection made more intense. The whole experiment was worked up to such a degree of perfection that it could not only be com- pared with the most renowned German pedigree cultures, but might even be considered as a test by which the value of the principle itself could be judged. Notwithstanchng this, the result was an absolute negative. It was simply impossible to get rid of tlie propensity to lie down. Xo real improvement could Ijc reached. After many years of hard work with steadily improved instru- ments and methods of testing and selection, the experiment had to be given up, since there was no ground for the hope of finally reaching the aim. At the same time, a considerable numljcr of other selec- tion ex])eriments had been carried on. Some of them gave the desired results, but others did not. The positive in- stances were only few, and although they have produced quite valuable new races, and have distinctly contril^uted to the improNement of agriculture in southern Sweden, it was clear that they could not afford sufticient proof for the reha- biUty of the principle. Success remained an exception, and exceptional improve- ments were not the aim of the work of the station. Dis- tinct problems it had to solve. It had to free the old varieties from definite defects, which impeded their more extensive use. A method wliich would give its results in some cases and in others not, could not be considered as involving the principle wanted. On the contrary, the conclusion had to be granted that in the positive cases, the result might be due to cjuite other causes, and that if it were only possible to dis- cover these, the whole system might be thrown over and replaced by sure and more reliable principles. The Ger- man idea that it was in the power of man to improve his NILSSON'S DISCOVERY 65 plants in an arbitrarily chosen direction, was manifestly con- tradicted by nature. The plant develops itself after its own capacity, but does not suffer itself to be forced into other ways. The principle of slow and gradual amelioration by so- called methodical selection was thereby condemned. The squarehead wheat showed itself to be as Httle amenable to improvement as the barley. Even the oats could not be im- proved. The new varieties which were occasionally ac- quired by the process might as well be considered as accidents. Among them was the Princess barley, which had been derived from the introduced Prentice barley, and wliich gained a high reputation and extensive distribution. In the same way, the Plumage barley yielded some valuable novelties. There was no reliabiUty in the method, nor could it be dis- covered why a result might be obtained in some cases, and in others not. It was clear that the solution of the great problem was to be sought in cpiitc another way. In the next chapter I propose to deal with the further experiments of the station at Svalof, which led to the dis- covery of the principle that the elementary species are the true material for selection, and that they are numerous and varied enough to satisfy all the present demands of practice. In order to make this description independent of all dis- cussions of the older principle, I will once more point out the essential differences between the German method and the work of the previous English breeders, as described in the former chapter. In doing so we have to exclude the views of Hallett, who partly participated in the ideas of his coun- trymen and partly held the same opinion as the Germans. The contrast now assumes this aspect: Improvement may be obtained by selecting single excellent individuals, and experience teaches that they will yield a constant and uniform progeny. This is the old EngUsh principle, by means of 66 PLANT-BREEDING which new races are not created but simply isolated from among a mixture. The alternative principle is, that a race may be improved and educated in arbitrarily chosen direc- tions. The original race is thereby assumed to be pure and uniform, and thus there is no reason for beginning with one single indi\idual. It is even better to start from a handful of ears, and to select in each generation a similar numljcr, in order to be sure that all characters which are not consciously considered in the selection may remain in the average condition which they held in the original variety. Concerning the causes of the improvement in this re- peated selection, two contrasting views have been discussed. Hallett assumed that variabiUty was induced or at least in- creased in the desired direction by his treatment. In Ger- many the opposite view was held, and it was even assumed that all changes induced by outer influences had no hered- itary power at all. They were considered as delusive, and the principle followed was to exclude them carefully. In- ternal causes were the real source of variabihty, and these had to be guided by selection. And since those internal causes, from their very nature, were not accessible to man, selection was considered the only real means of improvement. It worked slowly and often did not work at all, Ijut wherever a success was obtained, it was ascribed to the influence of this selection. ■ As I have already stated, methodical selection was as- sumed to produce races which could only be kept up to their high standard by a continuation of the selection. This point was of the highest practical interest for the breeder, since it kept the production of the seed-grains of his race in his own hands, at least for a long succession of years, and thereby enabled him to secure very considerable profits. On this account it is onlv natural that many breeders of cere- als of the present time still adhere to these old convictions. V NILSSON'S DISCOVERY 67 As an instance, 1 may cite the station for breeding cereals and potatoes at Nassenheide near Stettin in Germany, which is under the direction of Comit x\rnim Schlagentliin. Althougli in the main it offers for sale the new races produced at Svalof hx the methods to be described in our next chapter, it recommends the sale of the grains on the basis of the old views of dependency on elite strains instead of simply laying stress upon the purity of its products. Finally, a question is to be considered which has more of j scientific than of practical interest. Though the isolation of iadi vidua Is of exceptional excellence and the methodical improvement of races are absolutely contrasting principles, it is evident that they do not, in reahty, need to exclude one another. Quite on the contrary, it might be conceded that isolation is one process, but that the isolated types them- selves can afterwards be improved by selection. Tliis con- ception would lessen the difference between the opposite views and at the same time make them comply, at least apparently, with the idea of an origin of species in nature by means of slow and gradual changes. Theoretically, no objection could be made to this proposition and it would only remain to test its value by direct experiments. Practically, however, the proposition would be a purely hypothetical one, instead of being derived from the experience of the breeders, and it is manifest that these would thereby as well lose their significance as a support for Wallace's views on the ^ origin of wild species. C. THI<: SVALOF METHOD OF PRODUCING IMPROVED RACES. The criticism of the reliability of the German method of race-amelioration was part of the work during the first period of the operation of the experiment station at Svalof. It had not yet been conducted to a definite conclusion, when, in >