A DAISY WHICH RIVALS THE CHRYSANTHEMUM
AND OTHER IMPROVEMENTS IN DAISIES
The story of the origin of the Shasta daisy was told in an earlier volume. It will be recalled that this new flower, differing so widely in size and form and appearance from any daisy hitherto known, is in effect a new species produced by the combination of three species (and a fourth variety) that came respectively from Europe, from the eastern United States, and from Japan. The long series of experiments through which the European and American species were first hybridized, and the Japanese species subsequently brought into the combination, followed by new crossings and selections season after season through a long term of years, has been told in detail. Here it seems desirable to refer to more recent modifications of the Shasta, giving some specific hints as to its cultivation, and to review the work done with certain other daisy-like plants-to which also reference was made in an earlier volume-with particular reference to the interpretation of the results accomplished, in the light of the new information supplied us by observation of other series of experiments. First a few words as to the progress of the Shasta daisy, which, as we have learned, not only constitutes virtually a new species, but has given rise to a great variety of modified forms, all of them Shasta daisies, yet differing as markedly among themselves (in form at least) as, for example, different races of roses or poppies or dahlias differ. The racial strains of the three original parent species have been so recompounded, and, as regards their broader outlines, so truly fixed in the new species, that no one who sees a Shasta daisy can fail to recognize it as a Shasta-just as we recognize a rose or a poppy or a dahlia-even though the particular specimen under observation differs very radically as to size and form and arrangement of petals from anyone of the half dozen varieties that may be under observation at the same time. And the meaning of all this has been made clear to us in our studies of other forms. The separation of unit characters through hybridizing different species, and the recombining of these characters in the offspring of the second generation and subsequent generations, which is so vividly illustrated in the case of the Shasta, has been illustrated also in scores of other cases, until the principle involved has become so clear and obvious that no one is likely to overlook it. So, as I said, it is not necessary here to recapitulate the details of the series of hybridizing experiments through which the Shasta daisy was evolved. We shall be concerned with a few practical details as to the cultivation of a plant which is making its way into gardens everywhere, and which is sure to increase in popularity as the years go by.
SPREAD OF THE SHASTA
Probably no flower ever introduced has been more thoroughly appreciated and more rapidly and widely disseminated than the Shasta daisy. Owing to its hardiness, it can be grown anywhere from Alaska to Patagonia, and it requires almost no attention, except a biennial division of the clumps into numerous small plants, each piece of which will soon make a vigorous new clump. It is now widely grown throughout both temperate zones, and is rapidly becoming popular as a park and garden plant. It is greatly in demand for interior decorations, partly because its cut blossoms will last fully two weeks, whereas those of dahlias, roses, and lilies usually become quite unsightly after two or three days. Under no circumstances should the Shasta daisy be grown from seed, unless it be for the purpose of producing new varieties. No one would raise Chinese or Japanese chrysanthemums, roses, or carnations from seed, and hope to obtain the beautiful forms and colors peculiar to the selected plants. Strains produced by hybridizing vary more or less; upon this, of course, depends their chief value to the gardener who wishes to produce new varieties; but from the very fact of their mixed heritage these plants will not breed true from seed. But they are readily propagated in any desired quantity from the root of the mother plant. Reference has been made to the double forms that have appeared among the seedlings. Some of these bloom so freely as to destroy the vitality of the plants, unless some of the buds are removed. Other varieties have appeared with long, slender, lacinate rays, giving the blossoms a soft, feathery appearance; others still with curious twisted ray-flowers, or with long, tubular, or drooping ones, or those that are curled inward and upward, producing beautiful, cup-shaped blossoms; and all these in double form like roses, carnations or dahlias. All these curious forms can be reproduced indefinitely by division, but not one time in ten thousand can the best ones as yet be reproduced from seed.
PRACTICAL HINTS AS TO CULTURE
The Shasta daisy, though an exceptionally hardy plant, is, to a certain extent, sensitive to the conditions of its environment, and in order to secure the most thrifty plants and the most attractive blossoms it is necessary to follow certain rather definite rules of culture. The best results follow a division of the plants about every third year. If it is desired to develop strong, vigorous plants from the start, the old plants should not be allowed to bloom, else the cuttings taken from them will possess but scant reserve vitality. The plants should be divided into pieces as small as possible, care being taken to leave a bud and a few leaves and roots attached to the cutting, though the roots may be omitted, provided the shoots are properly treated. The long slender leaves should be cut back about one-half their length, so that they do not take too much moisture before the roots develop. After rinsing the cuttings in cold water they should be closely planted in a bed of sifted sand, indoors or out, according to climatic conditions. In order to settle the soil around the cuttings, they should be drenched with water, and a uniformly moderate supply of moisture should be maintained. If these instructions are followed, even the smallest, most unpromising cutting may develop into superior plants. When the slips are strongly rooted, they should be placed in a sunny place in rows eighteen inches to two feet one way by three or four feet the other. They should be thoroughly watered and treated like other garden plants. During July, August, and September each of the original cuttings should bear from twenty-five to fifty large, beautiful white blossoms. During the second season the best varieties should produce from one hundred to two hundred blossoms, measuring ordinarily from three to six inches in diameter. For the production of new varieties, Shasta daisy seed may be sown thickly in boxes of sandy soil or in out-of-door beds in California. If the seeds are those from the improved varieties, the resulting seedlings will bloom the first season, although the older varieties did not bloom till the second season, and then not as abundantly as these do the first. But the seedlings will form a motley company, many of them reverting to ancestral forms and departing widely from the characteristics that have made the fame of the Shasta daisy. But might we not by careful selection fix the Shasta as a form that would breed true from the seed?
COULD THE SHASTA BE FIXED?
The question is one that is not without practical interest. For there is obvious convenience in being able to grow an ornamental plant from the seed, even though it be possible to propagate it indefinitely by division. A small package of seeds may be shipped far more readily than roots or entire plants, and no doubt a large number of people will grow a plant from the seed who will not take the trouble to transplant roots or work from cuttings. So, as I say, the question as to the possibility of fixing the Shasta is not without practical importance. But the question also has a theoretical interest in connection with the general problems of the plant developer as applied not merely to this species but to many others. Our studies of many forms of plant life have taught us that the cultivated varieties of flowers, and of fruits and of vegetables as well, are so complex as to their heredities that-except in the case of certain annuals-they do not breed true from the seed, and are not habitually propagated in that way. Yet, on the other hand, we have seen that it is possible to fix new races by careful selection, and the principles according to which the experimenter works in effecting such fixation have been pointed out again and again. Making application of the knowledge thus gained to the case of the Shasta daisy, we need have no hesitancy in asserting that it would be possible to fix races of this plant so that they would reproduce their type with approximately the certainty from the seed as do, for example, the original parent forms from which they spring. But this task is as unnecessary as would be the task of fixing roses, carnations, or chrysanthemums. If inquiry is made as to the length of time required to effect such fixation of type, the answer can be given with a fair degree of certainty. Working along usual lines, by selecting the best specimens in a large company and in the successive year the best specimens among their progeny-extending, in other words, the method of selection through which the new races were originated-it would probably require from six to ten generations of selection to make sure of securing a specimen from the germ plasm of which disturbing hereditary factors had been eliminated by selection so that the factors that remain are those that produce the qualities that we desire to retain. But if it were feasible to devote the space and time to an experiment of a somewhat modified character, it would be possible, in all probability, to fix the type of any given race of Shasta daisies in a single generation and, after another generation to test the result, to secure seed that would reproduce plants duplicating the parent form as closely as offspring ever duplicate their parents. The practical manner of working through which this more rapid fixation of type would be effected would consist in selecting among a large company of seedlings grown from seed of a single typical plant the individuals that represent the parent form most closely. There are sure to be some of these among the thousands. These, indeed, are the ones that would be selected in any event by the experimenter who was planning to fix a type. Let the seed of each individual plant of these type specimens be sown in a separate plot; and in due course isolate each seedling so that each individual plant is self-fertilized. We shall then find that among the offspring of each plant there is the utmost diversity, but it will appear, in the next generation, that there are some plants that breed true to type and others precisely similar in appearance that produce diversified offspring. In other words, the practical method of isolating each individual through two generations would enable us to determine which ones have in their germ plasm only the factors that we desire to see perpetuated and which others have the mixed factors that we wish to see eliminated. The suggested manner of selecting by isolation of individuals merely enables us to go more directly to the goal. It does not differ in principle from the ordinary method of selection. But the isolation of each individual, so that its traits may be separately tested, enables us to reach the result in two years, instead of requiring perhaps from six to ten years. It will be recalled that it was through the application of this method that Prof. Biffen was enabled to isolate and fix his new race of wheat that is immune to rust in the third generation. But it must be recalled that Prof. Biffen was working with only a few hereditary factors or characteristics and that he was also working with a plant that is self-fertilized. To follow out the principle in the case of a plant like the Shasta daisy, in which a large number of hereditary factors are under consideration, would involve the handling of very much larger numbers of seedlings. And the fact that these must be isolated not merely in location but must also be guarded against cross-fertilization introduces a further complication. So it will be only an experimenter with plenty of time on his hands who could undertake to fix the type of the Shasta daisy by this rapid method. The experimenter who has numberless other plants to consider at the same time would be obliged to content himself with the older method, selecting, generation after generation, the individuals that came truest to type, and preserving their seed only from which to grow seedlings for another selection next season. But this method, while lacking the precision of the other, has served admirably well in a multitude of cases, some of which we have seen illustrated in recent chapters. So the experimenter who wishes to fix a race of Shasta daisies may with confidence go about the work along precisely the same lines that were used, for example, in the production of the wild heuchera with crinkled leaves-the method, for that matter, through which the races of Shastas were themselves developed after hybridization had supplied the material for selection.
It will be recalled that final hybridization through which the Shasta daisy was produced was made chiefly with an eye to the removal of the last tinge of duskiness and a greenish yellow shade that is more or less present in all white flowers, leaving a flower of snowy whiteness. It will be understood, also, that this quality of whiteness characterizes all the new races of Shastas-except one that has been bred for yellowness. The number of florets and their arrangement and form and size have been modified indefinitely, but these modifications do not in any way affect the color, except in case of one that showed a tendency toward yellow, and from this numerous yellow varieties, single and double, were developed. This color, however, fades in sunlight, and blanches in a few days. Aside from this, all Shasta daisies are characterized by their snowy whiteness. The improved varieties rival the variously modified chrysanthemums in size and form and in flexibility of florets; but they do not imitate the chrysanthemums as to variety of color. Possibly some varieties of Shasta may be modified in other directions as to color. One already shows pink on the outside of the ray flowers. One was found last year (1913) that had a faint shade of pink, and seed was saved. A pink Shasta daisy is therefore in prospect. There are other varieties of daisies, however, that show color variation. The whiteness of the ox-eye daisies both of Europe and America, and of the French marguerites, seems so typical that at first thought it appears anomalous that any daisy should depart from the traditional color. But, on the other hand, our studies of flowers have shown us that color is the least fixed characteristic of the floral envelope, and, reasoning from analogy, it would be rather surprising if there were not races of daisies, more or less closely related to the parents of the Shasta, that have colored blossoms. In point of fact, the Paris daisy has one lemon yellow variety; and there is a so-called daisy indigenous to South Africa, but for a good while cultivated in Europe, that has blossoms of a rather brilliant orange. This so-called African daisy, however, is not very closely related to the true daisies. The reader will recall a chapter of the first volume in which the story of this flower is told. It will be recalled that there is a closely allied species of daisy from the same region of South Africa that differs from the orange one chiefly in the fact that it is pure white. It will further be recalled that when these two species, the orange and the white, have been hybridized in Europe, the hybrid offspring shows an astonishing diversity of color. Not only oranges and yellows of many shades, but shades of purple and red also appear. It was by selection among the red hybrids, as will be recalled, that a so-called African daisy of a beautiful and uniform pink color was developed. It will further be recalled that among the hybrids were some which showed, on the backs of their petals, streaks of purple, showing that factors for blue color, as well as factors for yellow and red, are present. The interest of this experiment, as a mere illustration of a new race developed by hybridization, is not inconsiderable. But the chief interest of the experiment centers about the production of new colors which appeared to be alien to the hereditary traditions of the African tribe. Properly interpreted, the facts brought to light by these experiments fall in line with a large number of observations having to do with the colors of flowers, and give intimations of an interpretation of the entire subject of floral coloration. In attempting to interpret the facts, we should bear in mind what was learned in the preceding chapter as to the variable coloration of the poppies, and we shall have occasion to draw other illustrations from plants of a good many different types. We have found reason to believe that most flowers owe their color to a mingling of pigments, or at all events have in their hereditary strains the factors for many different colors, somewhat as even the purest tones on the canvas of the painter are usually the result of the blending of diverse pigments. We shall find reason to believe that even the white flower is not as a rule white because it lacks the factors for color pigmentation, but because it mingles these factors in such a way that they mutually antagonize, or neutralize, or "mask" one another. In this view, then, the production of a pink African daisy through the hybridizing of an orange and a white one may be regarded not as an anomalous phenomenon but as a typical one-albeit the experiment has a good measure of interest none the less.
VARIATION OF COLOR IN FLOWERS
The fact of color variation in the flowers is, as just stated, too obvious to escape notice of the least observant. A good many people, however, are unaware of the wide range of variation shown among wild species. It is sometimes assumed that color variation is due to the cultivation of plants; and, of course it is true that cultivation has resulted in developing races of flowers of diversified colors. But it is not to be supposed that these colors could have been developed in the short period during which the plants have been under cultivation had not the materials for color variation been present in the various hereditary strains. And it requires but the briefest search among wild flowers to show that color variation is by no means exceptional, but is, on the other hand, quite the rule here, even as among cultivated species. With a wild species, to be sure, there is usually preponderance of one color or another, because natural selection tends constantly to fix or accentuate one character and to minimize or eliminate another. In some respects the guide marks on the flower seem as important as the color itself. But that even under natural conditions it may not make a vast difference to the plant whether its advertising floral envelope, to attract the attention of insects, is of one color or another, is suggested by the frequency with which we find plants of the same species putting forth flowers widely different in hue. Let me cite a few instances, taken quite at random. They will suggest the extent to which one color may do service for another in the same species; suggesting also the probability that hereditary factors for all the colors manifested by different specimens of a species are well represented, at least in a latent condition, in the germ plasm of all specimens of the species. The nemophila, a common wild plant in California, has flowers that are generally clear, pure, skyblue, but this varies in different localities through all shades to snow white. Pink varieties are occasionally seen. Sometimes also the blue flowers are edged with white; and on occasion one sees white flowers with a blue edging, and sometimes a shade of yellow. The coast tree lupine, another wild plant, bears spikes of brilliant yellow flowers. But these may vary from lemon yellow to sulphur yellow, brownish yellow, smoky yellow, redish, pale blue, yellowish blue, dark blue, and pure white. Bright yellow is the typical or usual color, and white is quite rare. The other colors are not unusual. The Limnanthus douglasii is a wild swamp plant the flowers of which sometimes seem to carpet the ground. The upright, bell-shaped flowers are usually milk white. But I have received specimens from the Sierras that were yellow. The beard-tongue, a relative of digitalis, of the species known as Pentstemon barbatus, has flowers that vary from scarlet to almost pure yellow and white. The crimson clarkia and the bluebell have flowers the colors of which are indicated by their respective names; but both on occasion produce blossoms that are pure white. Everyone knows that the heliotrope, the lilac, and the violet, among cultivated flowers, are often represented by white forms-and the violet by other colors. The same is true of the whitelaria, the typical flowers of which are also blue, and of the trailing myrtle, the characteristic blue flowers of which are sometimes modified to crimson and to white. The gillias may show in the same patch flowers of the deepest crimson, others that are pale rosy crimson, yet others that are pink, and numerous ones that are pure white. These examples of variation in different flowers of the same species may be supplemented by mention of the curious flower known as cynoglossum, of the borage family, the flowers of which are blue in color until they are fertilized, then becoming deep red. Somewhat similar are the color changes of one of my new varieties of poppy, which vary from day to day. And this phenomenon of changing color while still retaining freshness may be linked with the observation that nearly all flowers change in color after they pass maturity, losing their brilliancy as they wither, and ultimately taking on altogether modified hues. With these illustrative cases of the varied coloration of flowers in mind-and of course the list might be extended indefinitely-it no longer seems strange that our orange and white African daisies have the potentialities of a pink daisy in their hereditary strains. There is every reason to suppose that the two African daisies are descended from the same original form. It is probable that the existing differences in their colors are due to somewhat recent modifications. Possibly the orange African daisy grew in the open, where it was subjected to the influence of sunlight; and the white daisy in a woodland or marsh where it was much in the shadow. It is a general observation that shade loving plants, like those that open their flowers in the twilight or at night, tend to produce white flowers or at most those dressed in light and pale colors; whereas the blues and oranges and reds are worn principally by flowers that grow in the open and put forth their advertisement for insects in the sunlight. So we may reasonably suppose that the white African daisy owes its present color to the influence of natural selection, and that it had among its ancestors plants that bore colored flowers. In any event, the orange African daisy has pigments of its own, without invoking the aid of ancestors, and their orange color shows that there are elements of red mixed with the yellow. These elements, sorted out through hybridization, sufficiently account for the pink progeny. But among the hybrids of the yellow and white African daisies, in addition to the pink ones, are numbers that are yellow; and, in about equal proportion, others that are white. These white individuals closely resemble their white parent; yet, as one of their parents was the orange daisy, it is obvious that they have in their germ plasm factors for yellow pigment, even though these are not revealed. These hybrids, notwithstanding the strain of yellow in their germ plasm, are as white to all outward appearance as their white parent; a fact which, taken by itself, sufficiently demonstrates that the white parent itself may have the submerged factors for pigment in its germ plasm. In point of fact, it appears to be sufficiently established that white flowers may be white not because they altogether lack hereditary factors for pigmentation, but for the paradoxical reason that they possess these factors in superabundance. We saw in our discussion of the colors of the poppy that there is reason to believe that two dominant colors, grouped together, may neutralize or mask each other and produce no tangible character. If we revert to an illustration used in another connection, in which we imagined that elfin architects are at work in the germinal nucleus, matching up the different hereditary factors to build a new organism, we may suppose that occasions arise when there is a superabundance of material (in the case under consideration, let us say, materials for both yellow blossoms and red blossoms), and that in such a case the architects might agree on a compromise in which neither yellow nor red pigment is used, the flower being allowed to remain white. We saw evidence that there are such latent color factors in flowers in such a case as that of the yellow poppy that when matched with a white one produced a galaxy of crimson poppies. The case of our orange African daisy mated with a white one is a variant on the same theme. And the illustration just cited of the different cases in which flowers of the same species have blossoms that may run the gamut of colors from scarlet through yellow to blue, or may lack pigment altogether, shows how common is the phenomenon of the mixture of factors for different colors in the same germ plasm. We shall perhaps not be far wrong if we assume that every colored flower has underlying potentialities of other colors than the one represented. And there is a good deal of evidence to suggest that yellow underlies red and is dominated by it when there is a mixture of different factors; that blue, lying toward the other end of the prismatic scale, stands rather by itself and in a way opposed to the other colors; and that white, as just suggested, may represent either the absence of factors for pigmentation or the presence of two or more conflicting pigments that neutralize each other. In another connection we shall discuss a theory as to the way in which the various colors, as utilized by the flowers, were introduced, and the significance of their various blendings.
-We shall find reason to believe that even the white flower is not, as a rule, white because it lacks the factors for color pigmentation, but because it mingles these factors in such a way that they mutually antagonize, or neutralize, or mask one another.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 9 Chapter 5