The survival of the unlike : a collection of evolution essays suggested by the study of domestic plants

Front matter

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Preface

For several years it has been my habit, when called upon to address horticultural societies, to choose some topic intimately associated with the evolution of domestic plants. My motives have been several. I have chiefly desired to attempt to answer many of the common questions which puzzle horticulturists by ap¬ pealing to the evidences of evolution, for I am con¬ vinced that many of these questions can be answered in no other ‘way. I have also desired to spread a knowledge of the evolution speculations and of the methods of research which they suggest, amongst those who deal with plants and animals, and who lead a rural life. Again, I have wished to make a record of a great class of most common and significant facts vitally related to the study of organic evolution, but which are almost wholly overlooked by students and philosophers. In making these essays, I have con¬ stantly had in mind the collation and publication of them, and I have, therefore, endeavored to discuss the leading problems associated with the variation and evolution of cultivated plants, in order that the final collection should be somewhat consecutive.

The results of this intermittent labor I now give

PREFACE.

to- those for whom it was from time to time conceived, — for horticulturists first, for evolutionists next. The essays are of unequal merit, and there are necessarily repetitions in them; but I conceive that they are the more valuable for having been written at dilferent times and for different occasions, for they thereby pre¬ sent the subjects in more diverse aspects. The audi¬ ences to whom the greater number of the essays have been addressed have been composed of persons who observe widely of facts, but who are unused to mak¬ ing broad inductions from ’them. It is only in the first two essays that I have ventured to state any general convictions respecting the bolder* problems of organic evolution, but I ‘count these of much less merit than the statements of many plain and simple facts of observation and experiment which are made in the humbler essays. If the author has been fortu¬ nate enough to make any contribution to positive sci¬ ence in these pages, it is probably that associated with the vexed question of bud -variation, which is chiefly presented in the third essay; but even this is novel only in its treatment. The underlying motive of the collection is the emphasis which is placed upon unlikenesses, and of their survival because they are unlike. The author also denies the common assump¬ tion that organic matter was originally endowed with the power of reproducing all its corporeal attributes, or that, in the constitution of things, like produces like. He conceives, as explained on pages 20 to 24,

PREFACE.

that heredity is an acquired force, and that, normally or originally, unlike produces unlike.

It may be well to state what are the chief lines of proof of evolution as they appeal to the author. A priori reasons for belief in the hypothesis are the two facts, that there must be struggle for existence from the mere mathematics of propagation, and that there have been mighty changes in the physical char¬ acter of the earth. These facts argue that organisms must either have changed or perished. To me, the chief demonstrative reason for belief in evolution is the fact that plants and animals can be and are modi¬ fied profoundly by the care of man. In fact, I should be convinced that the organic creation is an evolution if I had no other proof than this. But the proofs are abundant:

1. Those afforded by paleontology.

2. Those of embryology.

3. Those of comparative anatomy and structure.

4. Resemblances of types, which allow the objects to be classified. If species were specially created, there would have been no relationships.

5. The successive increase in complexity and dif¬ ferentiation, or divergence, in this classification, or the growth of the “tree of life.7’

6. The fact of adaptation to environment.

7. The vagaries of distribution. (See Essay XV.)

PREFACE.

8. The fact of variation, and the frequency of in¬ tergradient forms.

9. The observed behavior of animals and plants under the hand of man.

The reader who desires more explicit information upon the means of producing new varieties may con¬ sult “ Plant -Breeding, ” in which some of the more obvious speculations which are concerned w'ith the breeding of plants are set forth in some detail. His¬ torical narratives of our indigenous cultivated fruits will be found in ‘ ‘ The Evolution of our Native Fruits . ’ ’

L. H. BAILEY.

Cornell University,

Ithaca, N. Y., September 1, 1896.

PART I. Essays Touching the General Fact and Philosophy of

Evolution.

Page

I. The Survival of the Unlike . 13

II. Neo- Lamarckism and Neo- Darwinism . 55

III. The Plant Individual in the Light of Evolution.

The Philosophy of Bud -Variation, and its Bearing upon Weismannism . . 81

IV. Experimental Evolution amongst Plants . 107

V. Van Mons and Knight, and the Production of Varieties 138

VI. Some Bearings of the Evolution -Teaching upon Plant-

Cultivation . 162

VII. Why have our Enemies Increased? . 180

VIII. Coxey’s Army and the Russian Thistle. A Sketch of

the Philosophy of Weediness . 193

IX. Recent Progress in American Horticulture . 202

PART II. Essays Expounding the Fact and Causes of Variation

A. The Fact. Page

X. On the Supposed Correlations of Quality in Fruits 219

XI. The Natural History of Synonyms . 237

XII. Reflective Impressions of the Nursery Business . . 245

XIII. The Relation of Seed-Bearing to Cultivation . . . 251

B. The Causes.

XIV. Variation after Birth . 256

XV. A Pomological Alliance. Sketch of the Relation

ships between American and Eastern Asian

Fruits . 267

XVI. Horticultural Geography . 278

(ID

CONTENTS.

Page

XVII. Some Emphatic Problems of Climate and Plants.

Comprising “Speculative Notes upon Phenol¬ ogy (the Physiological Constant, and the Climatal Modification of Phenological Phenom¬ ena) ;” and “Some Interrelations of Climatology and Horticulture’ ’ . • • 288

XVIII. Are American Fruits Best Adapted to American

Conditions? . 311

XIX. Acclimatization : Does it Occur? . 320

XX. On the Longevity of Apple Trees. . . 334

XXI. Sex in Fruits . 347

XXII. Are Novelties Worth their Cost? . 356

XXIII. Why Do Promising Varieties Fail? . 364

XXIV. Reflections upon the Longevity of Varieties.

Comprising “Do Varieties Run Out?” “Are the Varieties of Orchard Fruits Running Out?” “Studies in the Longevity of the Varieties of Tomatoes” . 376

PART III. Essays Tracing the Evolution of Particular Types of

Plants.

Page

XXV. Whence Came the Cultivated Strawberry? . 400

XXVI. The Battle of the Plums . 418

XXVII. The Evolution of American Grapes . 431

XXVIII. The Progress of the Carnation. Comprising “Types and Tendencies in the Carnation;” “John Thorpe’s Ideal Carnation;” and “Bor¬ der Carnations.” . 438

XXIX. Evolution of the Petunia . 465

XXX. The Amelioration of the Garden Tomato. Com¬ prising 1 1 The Origin of the Tomato from a Mor¬ phological Standpoint;” “History of the Trophy Tomato;” “The Probable Course of Evolution of the Tomato;” and “Direction of Contemporaneous Improvement of the To¬

Index . 499

I

We all agree that there has been and is evolution; but we probably all disagree as to the exact agencies and forces which have been and are responsible for it. The subject of the agencies and vehicles of evolution has been gone over repeatedly and carefully for the animal crea¬ tion, but there is comparatively little similar research and speculation for the plant creation. This deficiency upon the plant side is my excuse for calling your atten¬ tion, in a popular way, to a few suggestions respecting the continuing creation of the vegetable world, and to a somewhat discursive consideration of a number of illus¬ trations of the methods of advance of plant types.

I.

Nature of the Divergence of the Plant and the Animal.

It is self-evident that the development of life upon our planet has taken place along two divergent lines. These lines evidently originated at a common point. The common life -plasma was probably at first more ani-

1 Originally an address before the Philosophical Club of Cornell University, April 20, 1896. Revised and presented, in part, before the American Philosophical Society, Philadelphia, May 1, 1896, and printed in the proceedings of the Society, vol. xxxv. pp. 88 to 110.

14 THE SURVIVAL OF THE UNLIKE. [i.

mal-like than plant -like. The stage in which this lifeplasma first began to assume plant -like functions is closely and possibly exactly preserved to us in that great class of organisms which are known as myeetozoa when studied by zoologists and as myxomycetes when studied by botanists. At one stage of their existence, these or¬ ganisms are amoeba -like, that is, animal -like, but at another stage they are sporiferous or plant -like. The initial divergencies in organisms were no doubt con¬ cerned chiefly in the methods of appropriating food, the animal -like organisms apprehending their food at a more or less definite point, and the plant -like or¬ ganisms absorbing food throughout the greater or even the entire part of their periphery. It is not my purpose to trace the particular steps or methods of these diver¬ gencies, but to call your attention to what I believe to be a characteristic distinction between the two lines of de¬ velopment, and one which I do not remember to have seen stated in the exact form in which it lies in my mind.

Both lines probably started out with a more or less well marked circular arrangement of the parts or organs. This was consequent upon the peripheral arrangement of the new cells in the development of the multicellular or¬ ganism from the unicellular one. A long line of animal life developed in obedience to this peripheral or rotate type of organization, ending in the echinoderms and some of the mollnsks. This type long ago reached its zenith. No line of descent can be traced from it, ac¬ cording to Cope. The progressive and regnant type of animal life appeared in the vermes or true worms, forms which are characterized by a two-sided or bilateral, and therefore more or less longitudinal, structure. The ani¬ mal-like organisms were strongly developed in the

ANIMALS AND PLANTS CONTRASTED.

power of locomotion, and it is easy to see that the rotate or centrifugal construction would place the organism at a comparative disadvantage, because its seat of sensation is farthest removed from the external stimuli. But the worm -like organisms “being longitudinal and bilat¬ eral, ” writes Cope, “one extremity becomes differen¬ tiated by first contact with the environment.7’ In other words, the animal type has shown a cephalic, or headforming, evolution in consequence of the bilateralism of structure. The individual has become concentrated. Out of this worm -form type, therefore, all the higher ranges of zootypic evolution have sprung, and one is al¬ most tempted to read a literal truth into David’s lamen¬ tation that “ I am a worm, and no man.”

If, now, we turn to plants, we find the rotate or peri¬ pheral arrangement of parts emphasized in all the higher ranges of forms. The most marked bilateralism in the plant world is amongst the bacteria, desmids, and the like, in which locomotion is markedly developed; and these are also amongst the lowest plant -types. But plants soon become attached to the earth, or, as Cope terms them, they are “earth -parasites.” They therefore found it to their advantage to reach ont in every direc¬ tion from their support in the search for food. Whilst the centrifugal arrangement has strongly tended to dis¬ appear in the animal creation, it has tended with equal strength to persist and to augment itself in the plant creation. Its marked development amongst plants be¬ gan with the acquirement of terrestrial life, and with the consequent evolution of the asexual or sporophytic type of vegetation. Normally, the higher type of plant bears its parts more cr less equally upon all sides, and the limit to growth is still determined by the immediate en-

THE SURVIVAL OF THE UNLIKE.

vironment of the given individual or of its recent ances¬ tors. Its evolution has been acephalic, diffuse, or head¬ less, and the individual plant or tree has no proper con¬ centration of parts. For the most part, it is filled with unspecialized plasma, which, when removed from the parent individual (as in cuttings and grafts), is able to reproduce another like individual. The arrangements of leaves, branches, the parts of the flower, and even of seeds in the fruit, are thus rotate or circular, and in the highest type of plants the annual lateral increments of growth are disposed in like fashion; and it is significant to observe that in the compositae, which is considered to be the latest and highest general type of plant -form, the rotate or centrifugal arrangement is most emphatically developed. The circular arrangement of parts is the typical one for higher plants, and any departure from this form is a specialization, and demands explanation.

The point 1 wish to urge, therefore, is the nature of the obvious or external divergence of plant -like and ani¬ mal-like lines of ascent. The significance of the bilateral structure of animal -types is well understood, but this significance has been drawn, so far as I know, from a comparison of bilateral or dimeric animals with rotate or polymeric animals. I want to put a larger meaning into it, by making bilateralism the symbol of the onward march of animal evolution, and circumlateralism (if I may invent the term), the symbol of plant evolution. The suggestion, however, applies simply to the general arrangement of the parts or organs of the plant body, and has no relation to structural characteristics and relationships. It is a suggestion of analogues, not of homologues. We may, therefore, contrast these two great lines of ascent which, with so many vicissitudes,

ARE PLANTS CATAGENETIC ?

have come up through the ages, as Dipleurogenesis and Centro genesis.

The two divergent directions of the lines or phyla of evolution have often been the subject of comment, but one of the sharpest contrasts between the two was made in 1884 by Cope, when he proposed that the vegetable king¬ dom has undergone a degenerate or retrogressive evolu¬ tion. “The plants in general,” he then wrote, “in the persons of their protist ancestors, soon left a free -swim¬ ming life and became sessile. Their lives thus became parasitic, more automatic, and in one sense degenerate.” The evolution of the plant creation is, therefore, held to be a phenomenon of catagenesis or decadence. This, of course, is merely a method of stating a comparison with the evolution of the animal line or phylum, and is, therefore, of the greatest service. For myself, however, I dislike the terms retrogressive, catagenetic, and the like, as applied to the plant creation, because they imply in¬ trinsic or actual degeneracy. True retrogressive or de¬ generate evolution is the result of loss of attributes. Cope holds that the chief proof of degeneracy in the plant world is the loss of a free -swimming habit; but it is possible that the first life -plasma was stationary: at any rate, we do not know that it was motile. Degeneracy is unequivocally seen in certain restricted groups where the loss of character can be traced directly to adaptive changes, as in the loss of limbs in the serpents. Re¬ tarded evolution expresses the development of the plant world better than the above terms, but even this is erro¬ neous, because plant types exhibit quite as complete an adaptation to an enormous variety of conditions as ani¬ mals do, and there has been rapid progress towards spe¬ cialization of structure. As a matter of fact, the vege-

2 SUR.

THE SURVIVAL OF THE UNLIKE.

table world does not exhibit, as a whole, any backward step, any loss of character once gained, nor any station¬ ary or retarded periods ; but its progress has been widely unlike that of the animal world, and it has not reached the heights which that line of ascent has attained. The plant phylum cannot be said to be catagenetic, but it is sni generis ; or, in other words, it is centrogenetic, as distinguished from dipleurogenetic.

The hearer should be reminded, at this point, of the curious alternation of generations which has come about in the plant world. One generation performs sexual functions, and the product of the sexual union is an asexual generation, and this, in turn, gives rise to an¬ other sexual generation like the first. In the low sexplants, as in some of the algae, the sexual generation — or the gametophyte, as it is called — generally comprises the entire plant body, and the asexual generation — or sporophyte — develops as a part of the fructifying struc¬ ture of the gametophyte, and is recognizable as a sepa¬ rate structure only by students of special training. In the true mosses, the gametophyte is still the conspicuous part of the plant structure. It comprises all that part of the moss which the casual observer recognizes as “the plant. ” The sporophytic generation is still attached to the persistent gametophyte, and it is the capsule, with its stem and appendages. In the ferns, however, the garnet - ophytic stage is of short duration. It is the incon¬ spicuous prothallus, which follows germination of the spore. Therefrom originates “the fern,77 all of which is sporophytic, and the gametophyte perishes. With the evolution of the flowering plants, the gametophyte becomes still more rudimentary, whilst the sporophyte is developed into the plant, tree or shrub, as we see it.

GENESIS OF DIFFERENCES.

The gametophytic generation is associated with the act of fertilization, the male prothallus or gametophyte de¬ veloping from the pollen grain and soon perishing, and the female prothallus or gametophyte developing in the ovule, and either soon perishing, or persisting, at least in the conifer -like plants, in the form of the albumen of the seed. The great development of the sporophyte in later time is, no doubt, a consequence of the necessity of assuming a terrestial life ; and with this development has come the perfection of centro - genetic form.

II. The Origin of Differences

The causes which have contributed to the origin of the differences which we see in the organic creation have been and still are the subjects of the most violent con¬ troversy. Those persons who conceive these differences to have come into existence full -formed, as they exist at the present time, are those who believe in the dogma of special creations, and they usually add to the doctrine a belief in design in nature. This doctrine of special cre¬ ation receives its strongest support when persons con¬ trast individual objects in nature. Certainly nothing can seem more unlike in very fundamental character than an insect and an elephant, a star fish and a potato, a man and an oak tree. The moment one comes to study the genealogies of these objects or groups, how¬ ever, he comes upon the astonishing fact that the an¬ cestors are more and more alike the farther back they are traced. In other words, there are great series of

THE SURVIVAL OF THE UNLIKE.

convergent histories. Every naturalist, therefore, is compelled to admit that differences in nature have some¬ how been augmented in the long processes of time. It is unnecessary, therefore, that he seek the causes of pres¬ ent differences until he shall have determined the causes of the smallest or original indifferences. It is thus seen that there are two great and co-ordinate problems in the study of evolution, — the causes of initial differences, and the means by which differences are augmented. These two problems are no doubt very often expressions of the same force or power, for the augmentation of a difference comes about by the origination of new degrees of difference; that is, by new differences. It is very probable that the original genesis of the difference is often due to the operation of the very same physiological processes which gradually enlarge the difference into a gulf of wide separation.

In approaching this question of the origin of unlike¬ nesses, the inquirer must first divest himself of the effects of all previous teaching and thinking. We have reason to assume that all beings came from one original life - plasma, and we must assume that this plasma had the power of perpetuating its physiological identity. Most persons still further assume that this plasma must have been endowed with the property of reproducing all its characters of form and habit exactly, but such assump¬ tion is wholly gratuitous and is born of the age-long habit of thinking that like produces like. We really have no right to assume either that this plasma was or was not constituted with the power of exact reproduction of all its attributes, unless the behavior of its ascendents forces us to the one or the other conclusion. Inasmuch as no two individual organisms ever are or ever have

UNLIKE PRODUCES UNLIKE.

been exactly alike, so far as we can determine, it seems to me to be the logical necessity to assume that like never did and never can produce like. The closer we are able to approach to plasinodial and unspecialized forms of life in our studies of organisms, the more are we impressed with the weakness of the hereditary power. Every tyro in the study of protoplasm knows that the amoeba has no form. The shapes which it assumes are individual, and do not pass to the descendants. To my mind, there¬ fore, it is a more violent assumption to suppose that this first unspecialized plasma should exactly reproduce all its minor features than to suppose that it had no distinct hereditary power, and therefore, by the very nature of its constitution, could not exactly reproduce itself. The burden of proof has been thrown upon those who attempt to explain the initial origin of differences, but it should really be thrown upon those who assume that life - matter was originally so constructed as to rigidly recast itself into one mould in each succeeding generation. I see less reason for dogmatically assuming that like produces like than I do for supposing that unlike produces unlike.

I advanced this proposition a year ago in my “ Plant - Breeding”* (pages 9 and 10), and I am now glad to find, since writing the above paragraph, that H. S. Williams has reached similar conclusions in his new “Geological Biology.” He regards mutability as the fundamental law of organisms, and speaks of the prev¬ alent notion that organisms must necessarily reproduce

*As an example of the common and unreserved acceptance of the notion that like produces like, I may cite the opinion of A. S., in a review of Plant-Breeding in the Bulletin of the Torrey Botanical Club (April, 1896) . He dogmatically asserts that the statement that inherent plasticity of organisms may allow of variation without an immediate inciting cause, is “certainly unscientific.” It is only fair to ask that he explain why it is.

THE SURVIVAL OF THE UNLIKE.

themselves exactly as “one of the chief inconsistencies in the prevalent conception of the nature of organisms.’ 7 “While the doctrine of mutability of species has gener¬ ally taken the place of immutability,” he writes, “the proposition that like produces like in organic generation is still generally, and I suppose almost universally, accepted. It therefore becomes necessary to suppose that variation is exceptional, and that some reason for the accumulation of variation is necessary to account for the great divergencies seen in different species. * * * * The search has been for some cause of the variation; it is more probable that mutability is the normal law of organic action, and that permanency is the acquired law.” I do not suppose that Professor Williams makes definite variation an inherent or necessary quality of organic matter, but that he conceives this matter to have had no original hereditary power, and that its form and other attributes in succeeding generations have been moulded into the environment, and that the bur¬ den of proof is thrown upon those who assume that life -matter was endowed with the property that like nec¬ essarily produces like. At all events, this last is my own conception of the modification of the lines of ascent.

This conception of the unstable constitution of the original forms of life is by no means novel, but it ap¬ pears to have been held most freely by those thinkers who are not themselves professed biologists. One of the best statements of it which I know is that of E. P. Powell in his powerful book, ‘ k Our Heredity from God.” “But Nature never fails to remind us,” he says, “that heredity is only a slowly established tendency, and that permutation is the original tendency in nature; for, if you succeed in breaking up an established order or

I.] HEREDITY AN ACQUIRED CHARACTER. 23

species, yon will find the most persistent effort necessary to prevent unlimited variation. * * * The difficulty is not so much to secure a new variety or a new species as it is to establish and confirm it.’7

In other words, I look upon heredity as an acquired character, the same as form or color or sensation is, and not as an original endowment of matter. The hereditary power did not originate until, for some reason, it was necessary for a given character to reproduce itself, and the longer any form or character was perpetuated, the stronger became the hereditary power.

It is now pertinent to enquire what determined the particular differences which we know to have persisted. The mere statement that some forms became sessile or attached to the earth, and that others became or re¬ mained motile, is an assumption that these differences were direct adaptations to environment. Every little change in environment incited a corresponding change in the plastic organization; and the greater and more various the changes in the physical attributes of the earth with the lapse of time, the greater became the modifications in organisms. I believe, therefore, that the greater part of present differences in organisms are the result, directly and indirectly, of external stimuli, until we come into those higher ranges of being in which sensation and volition have developed, and in which the effects of use and disuse and of psychological states have become increasingly more important as fac¬ tors of ascent. The whole moot question, then, as to whether variations are definite or multifarious, is aside from the issue. They are as definite as the changes in the environment are, which determine and control their existence. More differences arise than can persist, but

THE SURVIVAL OP THE UNLIKE.

this does not prove that those which are lost are any the less due to the impinging stimuli. Those who write of definite variation usually construe the result or outcome of some particular evolution into a measure of the vari¬ ation which is conceived to have taken place in the group. Most or all of the present characters of any group are definite because they are the survivals in a process of elimination; but there may have been, at va¬ rious times, the most diverse and diffuse variations in the very group which is now marked by definite attri¬ butes. As the lines of ascent developed, and generation followed generation in countless number, the organiza¬ tion was more and more impressed with the features of ancestral characters, and these ancestral characters are the more persistent as they have been more constant in the past. But these characters, which appear as hered¬ itary or atavistic variations in succeeding generations, were no doubt first, at least in the plant creation, the offspring, for the most part, of the environment react¬ ing upon the organism. As life has ascended in the time -scale and has become increasingly complex, so the operation of any incident force must ever produce more diverse and unpredictable results. What I mean to say is that, in plants, some of the variations seem to me to be the resultants of a long line of previous incident im¬ pressions, or to have no immediate inciting cause. Such variation is to all appearances fortuitous. It is, there¬ fore, evident that the study of the effects of impinging environments at the present day may not directly eluci¬ date the changes which similar conditions may have pro¬ duced in the beginning.

Whilst the steadily ascending line of the plant crea¬ tion was fitting itself into the changing moods of the

THE GROWTH - FORCE »

external world, it was, at the same time, developing an internal power. Plants were constantly growing larger and stronger or more specialized. The accumulation of vital energy is an acquired character, the same as pecu¬ liarities of form or structure are. It is the accumulated result of every circumstance which has contributed to the wrell- being and virility of the organism. The gar¬ dener knows that he can cause the plant to store up energy in the seed, so that the resulting crop will be the larger. Growth is itself but the expression or result of this energy which has been picked up by the way through countless ages. Now, mere growth is varia¬ tion. It results in differences. Plants cannot grow without being unlike. The more luxuriant the growth, the more marked the variation. Most plants have ac¬ quired or inherited more growth -force than they are able to use, because they are held down to certain limitations by the conditions in which they are necessarily placed by the struggle for existence. I am convinced that many of the members of plants are simply outgrowths resulting from this growth -pressure, or, as Bower sig¬ nificantly suggests (“A Theory of the Strobilus in Archegoniate Plants,’7 Annals of Botany, viii. 358, 359), they are the result of an “eruptive process.77 The push¬ ing out of shoots from any part of the plant body, upon occasion, the normal production of adventitious plant - lets upon the stems and leaves of some begonias (espe¬ cially Begonia phyllomaniaca) , bryophyllum, some ferns, and many other plants, are all expressions of the growth - force which is a more or less constant internal power. This growth -force may give rise to more definite varia¬ tions than impinging stimuli do; but the growth -force runs in definite directions because it, in its turn, is the