The Shasta Daisy
How A Troublesome Weed Was Remade Into a Beautiful Flower
"White is white," said one of my gardeners, "and all these daisies are white. They look just the same color to me." "Yes," I said, "white is white-there is no doubt about that. But these daisies are not white-and they do not look just alike to me. No one of them is pure white, but there is one that is nearer white than the rest, or else my eyes deceive me." All the other gardeners agreed with the first one, and it was some time before a visitor came who was not of the same opinion. Person after person was questioned, and each one declared that all the daisies in the row seemed to be pure white in color. No one could discriminate between them. But one day an artist from San Francisco visited the garden, and when she was shown the row of daisies and asked about their color, she answered instantly that there was one much whiter than all the rest; and to my satisfaction she indicated the one that all along had seemed quite different from the others to my eye. There was no question, then, that this plant bore flowers nearer to purity in whiteness than any others of all the thousands of daisies in my garden. Needless to say that particular plant was selected for use in future experiments, for the ideal I had in mind was a daisy that would be of the purest imaginable white in color. How the ideal was achieved-after fifteen years of effort-will appear in due course. The daisies in question, of which the plant bearing the nearly white flowers was the best example, had been produced by several years of experimentation which had commenced with the cultivation of the common roadside weed familiar to every one in the East as the ox-eye daisy, and known to the botanist as Chrysanthemum leucanthemum. This plant, which grows in such profusion throughout the East as to be considered a pest by the farmer, was not to be found in California until these experiments were begun. I brought the plant chiefly as a souvenir of boyhood days. But I soon conceived the idea of bettering it, for it had certain qualities that seemed to suggest undeveloped possibilities. In its native haunts of New England, the ox-eye, as everyone knows, is a very hardy plant and a persistent bloomer. Its very abundance has denied it general recognition, yet it is not without its claims to beauty. But it did not greatly improve or very notably change its appearance during the first few seasons of its cultivation at Santa Rosa; nor indeed until after I had given it a new impetus by hybridizing it with an allied species.
MATING THE OX-EYES
The plant with which the cross was made was a much larger and more robust species of daisy which I imported from Europe, where it is known colloquially as the ox-eye daisy, although the botanist gives it a distinct name, in recognition of its dissimilar appearance, calling it Chrysanthemum maximum. There is also a Continental daisy, by some botanists considered as a distinct species and named Chrysanthemum lacustre, which is closely similar to the British species, and of this seeds were secured from a German firm. Both these plants have larger flowers than the American daisy, but are inferior to it in grace of form and abundance of bloom. The plants have a coarse, weedy appearance, with numerous unsightly leaves upon their flower stalks, whereas the stalk of the American daisy is usually leafless. Notwithstanding the rather unsightly appearance of the European ox-eyes, I determined to hybridize them with the American ox-eye, in the hope of producing a plant that would combine the larger flowers of the European with the grace, abundant flowers, and early blooming qualities of the American daisy. The cross was first made with the English daisy C. maximum, by taking pollen from this flower to fertilize the best specimens of the American daisy that I had hitherto been able to produce. When the seeds thus produced were sown next season and the plants came to blooming time, it was at once evident that there was marked improvement. Some of the flowers appeared earlier even than those of the American daisy; they were very numerous, and were larger in size than the flowers of either parent. But all the flowers had a yellowish tinge, unnoticed by the average observer, but visible to a sharp eye on close inspection. And this tendency to dinginess in color was not at all to my liking. Further improvement was attempted by crossing the hybrid plant with the German daisy just referred to. A slight improvement was noticed, but the changes were not very marked. By selecting the best specimens of the hybrid, which now had a tripleparentage, I had secured, in the course of five or six years, a daisy which was very obviously superior to any one of the original forms as to size and beauty of flower, and fully the equal of any of them in ruggedness and prolific blooming. But the flowers were still disappointing in that they lacked that quality of crystal whiteness which was to be one of the chief charms of my ideal daisy. So year by year I anxiously inspected the rows of daisies in quest of a plant bearing blooms whiter than the rest; and seeds were selected only from the prize plants. The daisy spreads constantly, and one root stalk will, if carefully divided, presently supply a garden. But of course each plant grown from the same root stalk is precisely like the parent, and while I thus secured a large bed of daisies that combined approximate whiteness with all the other good qualities I was seeking, yet the purest of them all did not appear to my eye unqualifiedly white. And when my judgment was confirmed by the decision of the artist, I determined to seek some new method of further improvement that should rid my daisies of their last trace of offending pigment. In casting about for a means to achieve this end, I learned of an Asiatic daisy known to the botanist as Chrysanthemum nipponicuim; and presently I obtained the seed of this plant from Japan.
AID FROM JAPAN
This Japanese daisy was in most respects inferior to the original American ox-eye with which these experiments had started. It is a rather coarse plant, with objectionable leafy stalk, and a flower so small and inconspicuous that it would attract little attention and would scarcely be regarded by any one as a desirable acquisition for the garden. But the flower had one quality that appealed to me-it was pure white. Needless to say no time was lost, once my Japanese plants were in bloom, in crossing the best of my hybrid daisies with pollen from the flowers of their Japanese cousin. The first results were not reassuring. But in a subsequent season, among innumerable seedlings from this union, one was found at last with flowers as beautifully white as those of the Japanese, and larger than the largest of those that the hybrid plants had hitherto produced. Moreover the plant on which this flower grew revealed the gracefulness of the American plant, and in due course was shown to have the hardy vigor of all the species. From this remarkable plant, with its combined eration after generation the same influences from the soil and atmosphere, the stamp of these influences on its organic structure becomes more and more fixed and the hereditary influence through which these conditions are transmitted to its descendants becomes more and more notable and pronounced. So it is that a plant that has lived for countless generations in Japan has acquired a profound heredity tending to transmit a particular set of qualities; and when we hybridize that plant with another plant that has similarly gained its hereditary tendencies through age-long residence in Europe, we bring together two conflicting streams that must fight against each other and strangely disturb the otherwise equable current of hereditary transmission. Long experience with the hybrids of other species of plants had taught me this, and hence it was that I expected to bring about a notable upheaval in the hereditary traits of my daisies by bringing the pollen of a Japanese plant to the stigmas of my hybrid European and American ox-eyes. That my expectations were realized, and more than realized, is matter of record of which the present Shasta Daisy gives tangible proof. We shall see the same thing illustrated over and over again in our subsequent studies. Mixed ancestry, exceeded my utmost expectations in its combination of desirable qualities. I can hardly say, however, that the result achieved was a surprise; for my experience with hundreds of other species had led me to anticipate, at least in a general way, the transformations that might be effected through such a mingling of different ancestral strains as had been brought about. There was every reason to expect, while hybridizing the American and European ox-eyes, that a plant could ultimately be produced that would combine in various degrees all the qualities of each parent form. By selecting for preservation only those that combined the desirable qualities, and destroying those that revealed the undesirable ones, a fixed, persistent hybrid race that very obviously excelled either one of its parent forms was produced. Nor is there, perhaps, anything very mystifying about this result, for the simpler facts of the hereditary transmission of ancestral traits are now matters of common knowledge and of everyday observation. No one is surprised, for example, to see a child that resembles one parent as to stature, let us say, and the other as to color of hair and eyes. So a hybrid daisy combining in full measure the best qualities of the European and the American ox-eyes, as did my first hybrid race, perhaps does not seem an anomalous product, although certainly not without interest, in view of the fact that its parent stocks are regarded by many botanists as constituting at least two distinct species. But the final cross, in which the Japanese plant with its small flowers, inferior in everything except color, was brought into the coalition, calls for explanation. A general impression has long prevailed that a hybrid race whether of animals or of plants is likely to be more or less intermediate between the parent races; so perhaps the common expectation would have been that the cross between the new hybrid race of daisies and the obscure Japanese plant would result in a hybrid with medium-sized flowers at best, and, except possibly in the matter of whiteness of blossom, an all round inferiority to the best plants that I had developed. And in reality, there appeared the beautiful mammoth Shasta, superlative in all its qualities, surpassing in every respect each and all of the four parent stocks from which it sprang. This apparently paradoxical result calls for explanation. The explanation is found, so far as we can explain the mysteries of life processes at all, in the fact that by bringing together racial strains differing so widely a result is produced that may be described as a conflict of hereditary tendencies. And out of this conflict comes a tendency to variation. The reasons for this are relatively simple. Heredity, after all, may be described as the sum of past environments. The traits and tendencies that we transmit to our children are traits and tendencies that have been built into the organisms of our ancestors through their age-long contact with varying environmental conditions. The American ox-eye daisy, through long generations of growth under the specific climatic conditions of New England, had developed certain traits that peculiarly adapted it to life in that region. Similarly the European daisy had developed a different set of traits under the diverse conditions of soil and climate of Europe. And in the third place, the Japanese daisy had developed yet more divergent traits under the conditions of life in far away Japan, because these conditions were not only more widely different from the conditions of Europe and America than these are from each other, but also because the Japanese plant came of a race that had in all probability separated from the original parent stock of all the daisies at a time much more remote than the time at which the European and American daisies were separated.
THE PLANT AS A CAMERA
To make the meaning of this quite clear, we must recall that a given organism-say in this case a given stock of daisies-is at all times subject to the unceasing influence of the conditions of life in the midst of which it exists. The whole series of influences which we describe as the environment is perpetually stamping its imprint on the organism somewhat as the vibrations of light stamp their influence on a photographic plate. Indeed, as I conceive it, the plant is in effect a photographic plate which is constantly receiving impressions from the environing world. And the traits and tendencies of the plant that are developed in response to these impinging forces of the environment are further comparable to the image of the photographic plate in that they have a greater or less degree of permanency according to the length of time during which they were exposed to the image-forming conditions. If you expose a photographic plate in a moderately dim light, let us say, for the thousandth part of a second, you secure only a very thin and vague negative. But if without shifting the scene or the focus of the camera, you repeat the exposure again and again, each time for only the thousandth of a second, you will ultimately pile up on the negative a succession of impressions, each like all the rest, that result in the production of a strong, sharp negative. But if in making the successive exposures, you were to shift the position of the camera each time, changing the scene, you would build up a negative covered with faint images that overlap in such a way as to make a blurred and unmeaning picture. And so it is with the plant. Each hour of its life there come to it certain chemicals from the soil, certain influences of heat and moisture from the atmosphere, that are in effect vibrations beating on its protoplasmic life-substance and making infinitesimal but all-important changes in its intimate structure. The amount of change thus produced in a day or a year, or, under natural conditions, perhaps in a century or in a millennium, would be slight, for the lifetime of races and plants is to be measured not in these small units but in geological eras. Nevertheless the influence of a relatively brief period must make an infinitesimal change, comparable to the thousandth-second exposure of the negative. And when a plant remains century after century in the same environment, receiving generation after generation the same influences from the soil and atmosphere, the stamp of these influences on its organic structure becomes more and more fixed and the hereditary influence through which these conditions are transmitted to its descendants becomes more and more notable and pronounced. So it is that a plant that has lived for countless generations in Japan has acquired a profound heredity tending to transmit a particular set of qualities; and when we hybridize that plant with another plant that has similarly gained its hereditary tendencies through age-long residence in Europe, we bring together two conflicting streams that must fight against each other and strangely disturb the otherwise equable current of hereditary transmission. Long experience with the hybrids of other species of plants had taught me this, and hence it was that I expected to bring about a notable upheaval in the hereditary traits of my daisies by bringing the pollen of a Japanese plant to the stigmas of my hybrid European and American ox-eyes. That my expectations were realized, and more than realized, is matter of record of which the present Shasta Daisy gives tangible proof. We shall see the same thing illustrated over and over again in our subsequent studies. In offering this explanation of the extraordinary conflict of tendencies, with its resulting new and strange combination of qualities that resulted from the mixing of my various strains of daisies, it will be clear that I am assuming that the different ancestral races were all evolutionary products that owed their special traits of stem and leaf and flower to the joint influence of heredity and environment. I am assuming that there was a time in the remote past when all daisies had a common ancestral stock very different from any existing race of daisies.
TOURING THE WORLD
The descendants of that ancestral stock spread from the geographical seat of its origin-which may perhaps have been Central Asia-in all directions. In the course of uncounted centuries, and along channels that are no longer traceable, the daughter races ultimately made their way to opposite sides of the world. Some now found themselves in Europe, some in America, some in Japan. Thousands of years had elapsed since the long migration began; yet so persistent is the power of remote heredity that the daisies of Europe and America and Japan even now show numerous traits of resemblance and proof of their common origin that lead the botanist to classify them in the same genus. But, on the other hand, these races show differences of detail as to stem and leaf and flower and habit which entitle them to rank as different species. As the likenesses between the different daisies are the tokens of their remote common origin and evidences of the power of heredity, so their specific differences betoken the influences of the different environment in which they have lived since they took divergent courses. The Japanese daisy is different from the German daisy because the sum total of environmental influences to which it has been subjected in the past few thousand years is different from the sum total of influences to which the German daisy has been subjected. Not merely differences due to the soil and climate of Japan and Germany today, but cumulative differences due to ancestral environments all along the line of the migration that led one branch of the race of daisies eastward across Asia and the other branch westward across Europe.
ARE ACQUIRED TRAITS TRANSMITTED?
But all this implies that the imprint of the successive environments was in each case an influence transmitted to the offspring; and this is precisely what I mean to imply. To me it seems quite clear that the observed divergencies between the European and the Japanese daisy are to be explained precisely in this way. I know of no other explanation that has any semblance of plausibility. It is my personal belief that every trait acquired by any organism through the influence of its environment becomes a part of the condition of the organism that tends to reproduce itself through inheritance. In other words I entertain no doubt that all acquired traits of every kind are transmissible as more or less infinitesimal tendencies to the offspring of the organism. But it would not do to dismiss the subject without adverting to the fact that there are many biologists who dispute the possibility of the transmission of acquired traits. Indeed one of the most ardent controversies of recent years has had to do with that point; and doubtless many readers who are not biologists have had their attention called to this controversy and perhaps have received assurance that traits acquired by an individual organism are not transmitted. I shall not here enter into any details of the controversy, although doubtless we shall have occasion to revert to it. But it is well to clarify the subject in the mind of the reader here at the outset, by pointing out that this controversy, like a good many others, is concerned with unessential details, sometimes even with the mere juggling of words, rather than with essentials. As to the broad final analysis of the subject in its remoter bearings, all biologists are agreed. There is no student of the subject speaking with any authority today, who doubts that all animal and vegetable forms have been produced through evolution, and it requires but the slightest consideration of the subject to make it clear that Herbert Spencer was right when he said that no one can be an evolutionist who does not believe that new traits somewhere and somehow acquired can be transmitted. Otherwise there could be no change whatever in any organism from generation to generation or from age to age: in a word there would be no evolution. The point in dispute, then, is not whether any trait and modification of structure, due to the influence of environment, is transmissible, but only as to whether environmental influences that affect the body only and not the germ plasm of the individual are transmissible. But when we reflect that the germ plasm is part and parcel of the organism, it seems fairly clear that this is a distinction without a real difference. As Professor Coulter has recently said, it is largely a matter of definition. We shall have occasion to discuss this phase of heredity more fully in another connection. In the meantime, for our present purpose, it suffices to recall that biologists of every school will admit the force of the general statement that heredity, is the sum of past environments, and-to make the specific application-that our Japanese daisies and our German and American daisies are different because long generations of their ancestors have lived in different geographical territories and therefore have been subject to diverse environing conditions. In a word, then, the Shasta Daisy which stands today as virtually a new creation, so widely different from any other plant that no botanist would hesitate to describe it as a new species, owes its existence to the bringing together of conflicting hereditary tendencies that epitomize the ancestral experiences gained in widely separated geographical territories. Without the aid of man, the plants that had found final refuge in Europe and America and Japan respectively, would never have been brought in contact, and so the combination of traits that built up the Shasta Daisy 'would never have been produced. In that sense, then, artificial selection created the Shasta Daisy, but the forces evoked were those that nature provided, and the entire course of my experiments might be likened to an abbreviated transcript of the processes of natural selection through which species everywhere have been created, and are today still being created, in the world at large.
NEW RACES OF SHASTAS
Once the divergent traits of these various strains had been intermingled, the conflict set up was sure fo persist generation after generation. Each individual hereditary trait, even though suppressed in a single generation by the prepotency of some opposing trait, strives for a hearing and fends to reappear in some subsequent generation. So the plant developer, by keenly scrutinizing each seedling, will observe that no two plants of his hybrid crop are absolutely identical; and by selecting and cultivating one divergent strain or another, he may bring to the surface and further develop traits that had long been subordinated. Seizing on these, I was enabled, in the course of ensuing years, to develop various races of the Shasta, some of which were so different that they have been given individual names. The Alaska, for example, has even larger and more numerous blossoms than the original Shasta, with longer and stronger stems and more vigorous and hardy growth. The Westralia has blossoms of even greater size, and exceptionally long, strong and graceful stems, and the California has a slightly smaller flower but produced in great profusion; and its blossoms instead of being snowy white like those of the other races, are bright lemon yellow on first opening. Moreover the enhanced vitality due to cross-breeding and the mingling of different ancestral strains, was evidenced presently in a tendency to the production not merely of larger blossoms, but of blossoms having an increased number of ray flowers. The daisy is a composite flower, and the petal-like leaves that give it chief beauty are not really petals but are technically spoken of as rays. The flowers proper, individually small and inconspicuous, are grouped at the center of the circling rays. In all the original species the ray flowers constitute a single row. But the hybrids began almost from the first to show an increased number of longer and wider ray flowers, some of which overlapped their neighbors. By sowing seed from flowers showing this tendency, I developed after a few generations a strain of plants in which the blossoms were characterized by two rows of ray flowers instead of one. Continuing the selection, flowers were secured in successive generations having still wider and longer rays and increased numbers of rows, until finally a handsome double-flowered variety was produced. Aberrant forms were also produced showing long tubular ray flowers and others having the rays fimbriated or divided at the tip. And all these divergent and seemingly different types of flowers, it will be understood, have the same remote ancestry, and represent the bringing to the surface-the segregation and recombination of diverse sets of ancestral traits that had long been submerged. It is certain that no plant precisely like the Shasta Daisy or any one of its varieties ever existed until developed here in my gardens at Santa Rosa. But the hereditary potentialities of every trait of the new flower were of course present in one or another strain of that quadruple parentage, else they could never have made appearance in the ranks of the hybrid progeny.
-I entertain no doubt as to the transmissibility of inherited or acquired traits.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 2 Chapter 1