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With the present chapter we conclude our survey of the fruits proper, and it will be well to make a brief review of the subject, in particular with reference to the outlook, and the possibilities of further progress in the near future. In making this general review, we need not confine attention absolutely to the small fruits. Much that is said will refer to fruits in general. But doubtless there are larger opportunities for improvement with the berries and garden fruits than with the familiar orchard fruits, chiefly because the latter have been given a far larger share of attention by the horticulturist and fruit developer in the past. The large size and varied uses of apples, pears, peaches and plums, in particular, have made them popular everywhere, and have caused a vast deal of attention to be given them. So almost numberless varieties have been developed which meet the most varied requirements. But the small fruits have been the Cinderellas of the pomological family. Our own generation was first to give them proper recognition, and it remains for our successors to carry them forward to their true plane of utility. So it is these fruits rather than others that we shall have chiefly in mind, as the title of the present chapter would suggest. But I repeat that much that will be said applies to all marketable fruits, and even where a particular species is referred to, what is said is often susceptible of general application. Bearing this in mind, let us briefly review the story of the modern development of the small fruits, and with equal brevity outline a few suggestions as to the lines of future progress.


The consumption of fruit has increased more rapidly in the United States, and perhaps throughout the world, during the last one hundred years than has that of any other kind of food, with possibly the exception of nuts. The increase in the consumption of both fruits and nuts during the past twenty years has been particularly remarkable, and they are in fact coming to be regarded as food staples, as they certainly should be. As an illustration, take the case of the strawberry. This was about the first small fruit commercially grown in the United States to any great extent. Early in the 19th century a few were raised in New Jersey for the market in New York City. Those who first engaged in this enterprise soon found that to keep up with the increasing demand, it was necessary to go into the business on a much larger scale, and raising strawberries by the acre for the market became an industry. At the time it was prophesied that there would be an over-production of strawberries, and that they could not be sold. But now whole train-loads of strawberries and other berries are brought into New York City daily during the season. Probably a carload of strawberries is consumed today in the United States to every cultivated strawberry that was eaten one hundred years ago. The consumption of the tree-fruits, grapes, and other small fruits has increased in a somewhat similar proportion. America has had an important share in recent fruit advancement. When the immigrants came from other countries to America they usually brought with them some of the seeds or cuttings of their favorite fruits; these were planted and orchards were grown. And in the course of events, when the families began moving westward, they usually selected seeds from their best fruits for transplanting. In this way a constant and natural selection has been going on from the very first; the poorer varieties being discarded and forgotten, while those that filled a want and had proved productive and valuable were cherished. After this sifting process of the years, only a few of the older fruits, in proportion to the nurnber now cultivated, are still considered standard varieties. Especially during the last twenty-five years, new varieties of strawberries, raspberries, blackberries, currants, gooseberries, cherries, plums, prunes, apples, pears, peaches, nectarines, quinces, figs, and oranges have been produced and are now favorite fruits. The old varieties of these fruits, however, are slowly but surely being supplanted by still later productions.


This process of evolution is wholly imperceptible to the careless observer; but to one who watches closely the development of fruits, there is an unmistakable and rapid change now going on. Old orchards are continually being grafted over to new and improved varieties, while the new orchards added from year to year are planted to the latest standard fruits. This is especially true on the Pacific Coast, as competition is keen and the tests given fruits must be exacting. Luscious, sun-sweetened fruits must be produced which will bear shipping long distances, to less favored climes, retaining their form, color and flavor. Transcontinental shipping is one of the severest tests that can be applied to any fruit and it is distinctly a new test. Most of the older fruits had been selected for family use and home marketing; very few of them consequently could meet this new requirement. Notwithstanding the fact that practically all the best fruits in the world have been tested in California, only a few of the Eastern or European varieties have been able to meet the conditions here, and to fulfill all the requirements demanded. At present probably one-half of the fruits grown in California, with the exception of the French prune, are varieties that have originated, or at least have risen to commercial importance, within the state; and this statement applies with almost equal force to the states of Oregon and Washington. There is a great field of usefulness open to the enterprising plant breeder in the adaptation of fruits to different localities and climatic conditions, thereby extending the belt in which certain fruits can be raised. Some regions are too arid; some too cold, others too warm, or too damp and with too frequent rains for certain fruits. It is the mission of the plant-breeder to develop varieties that will withstand these conditions. What greater good can be accomplished than making exquisite fruits that will grow abundantly in sections of the country where none could be grown before?


In creating new varieties to meet local conditions, it is usually necessary to bear in mind not alone edible quality of fruit, but the constitution of the plant itself. Hardiness is often a sine qua non, particularly with fruits intended for the new regions of the Northwest, where the winters are extremely cold. Then nearly all kinds of fruits are subject to fungous diseases of some sort. These must be combated by developing hardy, resistant varieties. Some advancement has already been made in this direction; but much remains to be done. The careful plant-breeder will watch intently his stock and promptly discard all susceptible plants. It is in this way alone that such diseases can be thoroughly and permanently conquered. In some parts of the United States the sun's heat is too fierce and the air too dry for fruits to thrive which have been accustomed to more favorable conditions. For such regions varieties must be developed which are low, compact growers, producing an abundance of thick, leathery leaves, and fruit that will not easily sunburn. Some of the Eastern varieties, having become adapted to a moist climate, are open growers, bearing rather thin, delicate leaves. Such varieties are usually total failures when introduced in the arid Southwest. In developing a new fruit, the plant-breeder must not only meet the exacting demands of Nature, but also the exacting and increasingly complicated demands of the grower, the shipper, and the consumer; for together they constitute the jury that finally determines the value of his product. The tests of these jurists are applied from different standpoints and for different purposes. The grower is solicitous for an early-bearing, prolific tree, immune to fungous diseases or insect pests; one that will flourish with little care, pruning, or other attention. The shipper and dealer are unconcerned about the characteristics of the trees, or their productiveness, but they are eager for an attractive fruit-large, bright-colored, handsome; in particular for one that is very solid-so hard that it can be handled like a cannon-ball, which makes it a superb shipper. The consumer, on the other hand, prefers a reasonably tender, highly flavored, and easily digestible fruit. Unfortunately the consumer seldom obtains such a fruit unless it is grown nearby or within his own community; for the ideals of the shipper and the dealer, at variance with his preferences, intervene between him and the orchardist. For instance, better varieties of strawberries for table use have been developed than can be found in any market; better in quality, aroma and sweetness. The average consumer is never permitted to see them, or to experience their lusciousness. They are eliminated from the growers' list of fruits, because they do not meet the demands of the shipper and the dealer. The consumer usually obtains the best that the producer, the shipper, and the dealer can furnish, under the conditions with which they have to contend; the fault is not theirs, but that of modern civilization. I mention all this merely to show that varieties the production of which is useful and profitable, are not necessarily the most desirable for food purposes.


Yet the fault does not lie exclusively with the dealers. When a new fruit is first introduced it is difficult for the people to become adapted or accustomed to it, if it possesses new and strange peculiarities and qualities that are not understood or appreciated. I have found that it is just as difficult to adapt the people to a new fruit as it is to adapt a new fruit to the people. New varieties that at first are condemned, may be accepted later as standards, and become practically the only ones grown. The same law seems to hold true with fruits as with new ideas and new inventions in general; often these are at first condemned, but if possessing genuine merit they are finally recognized and appreciated. I have met this experience in the introduction of nearly all the new fruits that I have produced. It was ten years after the Burbank plum was introduced before people generally discovered that it was a valuable fruit. Now it is planted more widely than any plum on the globe, and thrives in almost all regions where plums can be grown. The excellent properties of the Wickson plum, now raised in most localities where plums are cultivated to any considerable extent, were for several years unrecognized. Today it is acknowledged to be the best shipping plum in existence, not only in America but in Africa, Australia, New Zealand, South America, and even in Japan. My Van Deman and Pineapple quinces were not very well received by some when first introduced; at present they are probably planted more than any other quinces in California, and everywhere acknowledged to be the best in quality, and in most of the eastern states the first-mentioned is considered the only variety worth growing, succeeding above others even in the coldest climates. But little merit was seen in the Phenomenal berry when first introduced, but during the past few years until quite lately the demand for the plant could not possibly be met. When the Crimson Winter Rhubarb was first introduced, the rhubarb growers in California paid no attention to it, and for some time refused to plant it at all. More recently, fortunes have been made in California and other regions having a mild climate by its culture, and today it is practically the only rhubarb being planted in all mild climates. People did not understand its new and peculiar characters and qualities; time was required to educate them. The same might be said of the Shasta daisy and several scores of other plants, and nuts, flowers, fruits and ornamental trees and vegetables which have been produced on my grounds. I have learned through experience that no new fruit will be fully appreciated, or its qualities generally known or recognized, for at least ten or twenty years. Corn, beans, peas, cucumbers, and similar plants can be tested in six months and accepted or rejected; but it requires years to test a new fruit so that its qualities may be thoroughly and generally appreciated.


We have seen that the adaptation of fruits to certain localities may be accomplished either by importation of plants developed elsewhere, or by producing the seedlings on the grounds, and selecting those that prove best adapted to the local conditions. In either case, a thorough study of each type of fruit in view of the needs and requirements of the location is absolutely necessary, in order to achieve success in the adaptation of the fruit. A section of country where strong winds prevail will require a fruit-tree with compact form and of firm wood. In climates of brilliant sunshine the tree must be protected with an abundance of thick, heavy foliage. Some trees will not thrive in a dry soil; others fear moisture. And there may be differences as to these propensities among plants grown from the same lot of seed; and, indeed, from seeds produced by the same plant. Therefore not only the type but the individuality of the plant must be considered, adapting it to certain conditions. If the quality of hardiness in fruit is required it may he attained through proper methods. In regions where insect and fungous diseases thrive it is necessary to evolve fruit-trees which are resistant to such pests; and there is no other way of reaching a satisfactory conclusion regarding their resistant powers than to grow them where they are exposed to their foes. All of this cannot be accomplished in a brief time. It requires the most persistent labor and unyielding patience. Any recognized "fruit quality" can be intensified, almost any desired quality can be attained, through intelligent observation, selection, and patient waiting. But not without toil; nor without careful heed to such measures as will assure the co-operation of Nature. Says Emerson: "The ripe fruit is dropped at last without violence, but the lightning fell and the storm raged, and strata were deposited and uptorn and bent back, and Chaos moved from beneath, to create and flavor the fruit on your table today." Let the plant developer ponder and heed that saying, and realize that at best it is given him not to create or overturn, but only to have a slight selective and directive influence in the great Scheme of Plant Evolution.


We have viewed in detail the story of the development of the different fruits, and have observed many anomalous products. We have witnessed the creation of new species, and have seen that rules applying to the hybridizing of certain forms appear to be quite abandoned in the hybridizing of others. But of course we know that the underlying principles are everywhere the same, and that seeming divergencies in their application to different species are but modifications of the same laws to meet varying conditions. The wise plant developer must be able to look beneath the surface and discover the underlying harmonies. Otherwise he will often make mistaken interpretations, and will perhaps give up an experiment when the goal was just within reach. Perhaps it may be helpful if now, by way of summary, we review in their broader outlines, a few of the principles that have been illustrated by specific cases in the preceding volumes, and offer an added word of explication that may be of aid to the general reader in clarifying his view of complex plant hybridizations, and to the plant experimenter in giving clues that may prove advantageous in his work in the field. Let us recall, as the text for our first illustration, the simplest case of plant hybridization. When, let us say, a thorny and a thornless blackberry are crossed, the offspring are all thorny. But in the next generation a certain proportion of the offspring are thornless. A corresponding case is that of the ordinary blackberry crossed with the white blackberry. All the offspring of the first generation are black, but whiteness reappears among their descendants. Let us recall, further, that the process of hybridization consists essentially in bringing the nucleus of the pollen cell in combination with the nucleus of an egg cell. Also let us bear in mind a computation that we were able to make with the aid of the physicist, by which we were made aware that the germ cell itself is a highly complex structure with diversified component parts, each of which may be thought of as having as much individuality as any member of a developed organism We saw that, even if we considered the individual parts or members of a germ cell to number a thousand or more, there are available many billions of atoms to make up each member. Let us then, finally, recall the teaching of the modern biologist, who gives us reason to believe that, just as each individual higher organism is produced by the union of two complementary elements, male and female, so there is union of complementary elements within the intimate structure of the ovule itself to form each new character. That is to say, using the accepted terminology, it is necessary in building up any character that is to be made manifest in the future adult organism, that there shall be a blending of two hereditary factors, which we may now think of as individual members of the germ plasm colony or organism. For example, there are factors of thorniness and factors of thornlessness in the germinal cell of the blackberry. There are color factors for blackness and for whiteness in the case of our other blackberry. It may be in any given case that the two factors united both represent thorniness, in which case the future plant will bear thorns. It may be, on the other hand, that the two factors both represent thornlessness, and in that case the future plant will be thornless. Yet again there may be a union of a thorny factor with a thornless factor; and in this case, as we have seen, thorniness will prevail because, as we say-although, of course, our explanation only states the matter over again in another way-the thorny factor is dominant and the thornless factor recessive in this particular combination. Changing our terms to suit the case, the same principles apply to our black and white blackberries. And in each case, it will-be recalled, the germ cell that bears only dominant factors will breed true to the dominant quality; the germ cell that bears only recessive factors will breed true to the recessive character; and the germ cell that bears the two conflicting factors will have progeny in which these factors are separated and reassembled in various combinations, thus accounting for the reappearance of the latent or recessive character.


All this is familiar to us and has been illustrated over and over again from practical cases in the course of our studies. And we have agreed that the really mysterious part of the entire process is the fact that the hereditary factors are able to combine with such certitude and grow and multiply and reproduce themselves indefinitely. This part of the procedure is indeed mysterious and beyond the fathoming of the human mind. Yet perhaps it may be made to seem at least a little more tangible and explicable, even if not less mysterious, by an interpretation in which we are permitted for once to make use of the imagination. Suppose we imagine the existence within the complex structure of the infinitesimal germ plasm organism of a being of human intelligence, but of atomic proportions-an elf that has control of the hereditary factors, considered now as material entities, and directs their use in the building up of a new organism, somewhat as a human architect directs the use of material in the construction of a human habitation. Let us then assume that the material making up the nucleus of a pollen cell as it comes to the ovule of a flower and is brought in contact with the nucleus of the ovule, is in charge of one such elfin architect, and that the materials of the nucleus of the ovule itself are in charge of another elfin architect. The task of building the new structure that is to result from the union of the two nuclei devolves upon these two elfin architects jointly. They must work in co-operation and their decisions will determine how the hereditary factors shall be combined in building the new organism. Suppose, now, that the particular case that is before us is that which arises when some colossal plant-developer with his crude manipulations has succeeded in transferring a pollen grain of a thorny bramble that bears white berries to the pistil of a thornless bramble that bears black berries, and that the respective nuclei of pollen-grain and ovule have come together. The elfin architects compare notes, inspect their respective blue prints and charts and tables of specifications, and set to work. For a time they get on very well. There are factors for general size and foliage and form of plant; for time of flowering and appearance of flower cells; for root system and shape of leaf and shape of future fruit, and a multitude of other details in regard to which there is perfect agreement. In all these cases the factor that A represents fits perfectly into the factor that B represents, and the work of building the future plant goes on apace. But presently, as they have built upward from the root and outward from the center, they come to the specifications for texture of stem. And here at once there is disagreement. Elf A finds that his specifications call for a thorny stem, but the factor that elf B represents calls for a smooth stem. And at once there is a quarrel. "Whoever heard of a brier bush without protective briers?" demands elf A. "I have the honor to represent such a one," says the other. "But the thing is a departure from all the traditions of good brier architecture," insists A. "Moreover you cannot possibly fit the materials together without getting some brier material." And this argument prevails. When the factors are examined, it is obvious that if they are put together the thorny factor will overlie the thornless one, somewhat as, a carved stone might overlie a smooth stone in a human dwelling. So it is admitted that the new organism must have a thorny stem. Now all goes well again until the two architects come to the building of the future fruit. Character of flowers, time of fruiting, and general structure of the berry itself are all arranged. But just as the last detail was almost completed there is again a disagreement. It is discovered that A's plan calls for a white fruit, B's plan for a black fruit. "Whoever heard of a white blackberry?" demands B, turning thus rather neatly the argument that the other elf used about the thorns. "The thing is ridiculous." "I represent a white blackberry," A replies, let us hope with dignity. "Well, there isn't any way of blending white paint and black and keeping things white, is there?" B continues. And this argument is conclusive. The two color factors are assembled, and it is conceded that the future plant will bear black fruit. The black pigment overlies the white like a double coat of paint, and a black fruit is provided for. When the elfin architects have finished their task, then the factors representing the materials of the two germ cells have all been satisfactorily paired, and provision has been made for a future bramble that will have a thorny stem and will bear black berries-a plant that is unlike either parent, although built of no material except factors drawn from the two parents. Recall, however, that the factors for thornlessness and for white fruit were not eliminated. They were only overlaid by the opposing factors. They go forward in the germ plasm, each pair of factors being constantly multiplied through division in the mysterious way that characterizes living matter, so that for each factor that entered into the original structure, there are now multitudes of factors. And in the next generation, when new pairs of elfin architects are making their plans, it will be possible to re-assort the materials (in building a large number of new structures that we call offspring of the second generation), making some combinations that will include two smooth stemmed factors and two white-fruit factors, and thus giving us a certain number of seedlings of this second generation that will have smooth stems and will bear white berries-which chances, perhaps, to be what the crude human experimenter is seeking.


But now let us attend to a case in which a more complex hybridization was made; that, let us say, in which the pollen of an apple was brought to the pistil of a dewberry. Now we must call attention to a feature that we have ignored heretofore-the segregation of body plasm and germ plasm at an early stage of the union. The coming together of the two germ plasms gives a stimulus to growth. The berry develops, and a drupe is formed that is like a dewberry because the body plasm of the dewberry is acting as carrier. That is to say, the dewberry is the pistillate parent. The elfin architects in a single ovule get together. They separate out the body plasm, and, although there is conflict, it appears that the material will permit the building of a root and stem and leaf system that will answer after a fashion-though a sad departure from tradition. A big rambling bush that will try to ape both dewberry and apple tree will result. But in the matter of the architecture of the germ plasm for the newy organism through which the race is to be perpetuated, difficulties arise at the outset that are almost disheartening. There has been trouble enough in getting the factors together to make any sort of stem and leaf and flower. But all this was nothing compared to the difficulties that arise when they get to the fruit. "Specifications for fruit," says elf A consulting his blue print: "A big, pulpy fruit, about four inches in diameter, called an apple." "Not at all," cries B, consulting his own blue print. "The fruit is a small berry about an inch long, with many drupelets each having a seed at its center-in short, a blackberry." How can two elfin architects hope to harmonize materials like that? It is like getting together two human architects to combine materials for a habitation and finding that the material one has to offer for the house are blocks of stone four feet square while the other has only pebbles. And as the conference goes on, the points of discrepancy become only the more apparent. All the differences that are manifest between a blackberry bush and an apple tree, and between an apple and a blackberry-together with a multitude of intimate distinctions that the crude human senses cannot fathom-are represented by factors that obviously cannot blend. So, after studying the matter over and wrangling about it till their heads ache, the elfin builders give up the thing as a bad job. Their germ factors lie in separate piles unassembled and incapable of being assembled; and the result is that no provision will be made for fruit in the future plant. In other words the plant will be sterile, and that particular double stream of germ plasm will cease to be perpetuated.


This, then, is what may be imagined to occur when there is too great difference of materials. It may be left to the reader's imagination to make for himself a picture of the various activities of the elfin architects in those cases where the diversity between the different hereditary factors is greater than that between the two kinds of blackberries. but less than that between the apple and the dewberry. We saw in such cases as that of the Primus berry and the Sunberry that when the two germ plasms were at just a certain stage of divergence the resulting hybrid presented a compromise of characteristics. We may suppose that the elfin architects in the germ plasm are in such a case to be compared with human architects, one of whom, let us say, presents blocks of stone as the chief building material while the other presents bricks. Stone and bricks cannot be blended, but they may be variously combined, for example, placed in alternate layers, to make a structure that is neither a stone house nor a brick house, although it is a house built of both stone and brick. In the same way the Primus berry is neither a blackberry nor a raspberry, although its component hereditary factors are all either blackberry or raspberry factors. But we need not attempt to carry the illustration further. The reader who has followed it may make his own application, in reviewing the facts as to the various results of hybridizing species more or less closely related that have been detailed in the preceding chapters. To some readers the entire illustration of the elfin architects may seem whimsical. But it is presented in all seriousness in the hope that it may serve a useful purpose. Not that I would for a moment be understood as suggesting that any such infinitesimal creatures with human intelligence are really domiciled in the germ cell. But to personify thus the inscrutable forces through which the building together of the hereditary factors is brought about may serve to give tangibility to the forces of heredity, and to help the reader to memorize the facts already presented, and gain clearer insight into the principles that underlie them. It may chance that such a personification will enable the plant developer to see a little more clearly into the nature of the phenomena that are presented before his eyes when two plants are hybridized; and that he may thus be enabled to interpret the phenomena in a way that will be to his practical benefit. As elsewhere pointed out, the incorrect interpretation of the early results of a hybridizing experiment may put the experimenter off the track and lead him to give up an effort which would have led to complete success had it been carried forward another generation. But, in any event, whether or not the reader finds the elfin architects of the germ plasm an aid in his interpretation of the phenomena of heredity, let the would-be developer of new fruits, or the improver of old ones, bear in mind, as the last word that experience can offer on the subject, the principle that progress must be sought through the careful selection of types that vary in the direction of desired progress; and that in a vast majority of cases such variation may be brought about, and in a sense directed, through hybridization.

-The successful plant developer must be able to look beneath the surface of his plants to discover and utilize the underlying harmonies.

This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 6 Chapter 9