i / JEAN «. BILL LANE HORTICULTURAL LI3RAR.Y */£ M «y (IOW PLANTS AIM'. TRAINED WORK FO J'TIIER BURBANK Sc. D ARTIFICIAL RAIN -IN MR. BURBAXK'S GARDEN Mr, Burbank uses and recommends a sprinkling apparatus like that shown here. It consists of long pipes attached to a hose, each pipe having little nozzles at intervals of a few inches, thus send- ing forth a series of tiny streams which, rising high in the air, descend on the plants in a shower that closely simulates rain from the clouds. The pipes can be turned to throw the spray in either direction, and to regulate the distance at which the shower descends. Remem- ber always that water is food for the plants — absolutely indispensable food. RR & SON COMPANY YORK .HM TTI T/TIAH JAIDFTITHA HOW PLANTS ARE TRAINED TO WORK FOR MAN BY LUTHER BURBANK Sc. D USEFUL PLANTS VOLUME VI EIGHT VOLUMES ILLUSTRATED PREFATORY NOTE BY DAVID STARR JORDAN P. F. COLLIER & SON COMPANY NEW YORK Univ, Librae H Sante Cruz 1999 Copyright, 1914 BY THE LUTHER BURBANK SOCIETY All rights reserved Copyright, 1914 BY THE LUTHER BURBANK SOCIETY Entered at Stationers' Hall, London All rights reserved Copyright, 1915 BY THE LUTHER BURBANK SOCIETY Entered at Stationers' Hall, London All rights reserved Copyright, 1921 BY P. F. COLLIER & SON COMPANY MANUFACTURED IN U. S. A. CONTENTS PAGE IMPROVEMENTS IN WHEAT,, OATS, BARLEY 7 FOOD FOR LIVE STOCK 27 A RICH FIELD FOR WORK IN THE TEX- TILE PLANTS ; 47 PLANTS WHICH YIELD USEFUL CHEM- ICAL SUBSTANCES . ... . . 67 RECLAIMING THE DESERTS WITH CACTUS 95 OTHER USEFUL PLANTS WHICH WILL REPAY EXPERIMENT 171 WHAT TO WORK FOR IN FLOWERS . . 197 WORKING WITH A UNIVERSAL FLOWER — THE ROSE 225 IMPROVING THE AMARYLLIS . . . .251 PRODUCING AN ENTIRELY NEW COLOR . 279 A DAISY WHICH RIVALS THE CHRYSAN- THEMUM 307 EXPERIMENTS WITH THE OLD RESPONSIVE DAHLIA 333 1 1— Vol. 6 Bur. LIST OF ILLUSTRATIONS ARTIFICIAL RAIN IN MR. BURBANK'S GARDEN Frontispiece PAGE RESULTS OF WHEAT EXPERIMENTS . . 14 A SHEAF OF OATS 18 SAMPLE HYBRID SUNFLOWER ... 22 THE FLAX PLANT ...... 50 COTTON FLOWER AND SEED HEAD . . 58 SUGAR CANE TASSELS 70 VARIETIES OF SORGHUM 78 A HOP-FIELD VISTA 84 SUGAR BEETS AT THE FACTORY ... 90 THE CANDLE CACTUS 98 THE GRAVITY CACTUS 104 THE PROLIFIC CACTUS 110 YOUNG ROYAL CACTUS PLANTS . . . 116 THE HEMET CACTUS 122 THE MELROSE CACTUS 128 3 4 LIST OF ILLUSTRATIONS PAGE SPINELESS CACTUS SHOWING Six MONTHS' GROWTH 134 A FRUIT COLONY 140 CACTUS BLOSSOMS . 148 CACTUS CANDY 156 A CACTUS- SLAB FAN ...... 164 PAMPAS GRASS 180 VARIATION IN COLOR AS WELL AS IN FORM 200 PERENNIAL PEAS 210 A YELLOW TRITOMA OR "RED- HOT POKER" 218 THE BURBANK ROSE 228 A NEW YELLOW RAMBLER . . . . 232 ROSES AT SEBASTOPOL 236 GLIMPSE IN THE PROVING GROUND . . 240 A MAMMOTH BOUQUET . t.- .. 244 THE CORONA ROSE ...... 248 GIANT AMARYLLIS 252 H^EMANTHUS BLOSSOMS 256 SEEDLINGS OF THE BELLADONNA LILY . 260 A DOUBLE AMARYLLIS 264 LIST OF ILLUSTRATIONS 5 PAGE A BURBANK AMARYLLIS 268 ONE OF THE NEW CRINUMS .... 272 SEED PODS OF THE CRINUM .... 276 A NEW SHIRLEY POPPY 282 ANOTHER NEW SHIRLEY POPPY . . . 288 ANOTHER NEW POPPY 294 A HYBRID POPPY 298 THE BURBANK ART POPPIES . . . 302 A SEMIDOUBLE DAISY . . . . . 310 LACINIATED PETALS 316 A BOUQUET OF SHASTAS 322 A WHITE GLADIOLUS 328 A PRIMITIVE TYPE OF DAHLIA . . . 340 A COMMON TYPE OF THE MODERN DAHLIA 348 IMPROVEMENTS IN WHEAT, OATS, BARLEY MENDELIAN CLUES THE essential facts of Mendelian discovery with regard to "unit" characters and their grouping into pairs, in which one character is dominant and one recessive, have been more than once called to our attention and have been illustrated again and again with instances drawn from my own plant experiments. The cases of the black and white blackberries, the thorny and thornless blackberry, and of stone-bearing and stoneless plums, among others, will be recalled. But we have also observed cases in which the characters of two parents seemed to be blended in the offspring, there being no clear dominance of one character over another. Such was the case, for example, with the sunberry, the primus berry, the plumcot, and many others. Now it is peculiarly interesting to note, in the light of our experiments with various fruits and 8 LUTHER BURBANK flowers of widely different orders, that Professor Biffen was able to analyze the diverse qualities of the various wheats with which he experi- mented and to discover that different groups of unit characters operated differently in heredity. Some of the pairs showed dominance and reces- siveness; others showed an irregular or partial dominance; while other pairs showed the blending of characters, so that the offspring was intermediate between the parents, there being no apparent tendency to dominance or recessiveness. Yet all of these characters, whether manifest- ing the phenomena of dominance in the hybrid of the first generation or not, showed the same tendency to segregation in the succeeding gener- ation, and to segregation along the familiar Mendelian lines; that is to say, one offspring in four would reveal the first character only, the second and third offspring were mixed as to the pair of characters, and the fourth would show only the second character. It was necessary only to plant the individual grains of wheat in plots by themselves, and to note the qualities of the grains of each (that is to say, the qualities of the offspring of the first filial generation) to make sure as to the position of each individual in the Mendelian scale WHEAT, OATS, BARLEY 9 (whether pure or mixed in its heredity as to its given factor), and thus to be able to select pure types that would breed true; and, what is per- haps equally important, to eliminate the impure types that would not breed true. DOMINANT AND RECESSIVE CHARACTERS It will be of interest to note a few characters that Professor Biffen particularly studied and the groups into which they fall. As to characters that show the phenomena of pure dominance and recessiveness, the following among others were clearly revealed: Beardless ears of grain are dominant to the bearded ears ; keeled glumes to round glumes ; lax ears to com- pact ears; red chaff to white chaff; red grain to white grain; thick and hollow stem to thin and solid stem; rough leaf surface to smooth leaf surface; bristles on the stem to a smooth stem; hard translucent endosperm (central grain sub- stance) to soft opaque endosperm; and, finally, susceptibility to the attacks of yellow rust was dominant to immunity to yellow rust. This implies, as the reader is aware, that in each case of those just listed, when two plants represented by the opposite characters are crossed, the offspring will show the first-named character to the exclusion of the other in the first 10 LUTHER BURBANK generation, but the excluded character will reappear in one-fourth of the offspring of the second generation. Breeding a wheat with beardless ears and white grain, for example, with a wheat having bearded ears and red grain, all the progeny will be beardless and red-grained; but bearded ears and white grain will reappear, in various com- binations, in one-fourth of the progeny of the second generation. It is never safe -for the plant developer to draw exact inferences as to the hereditary tendencies of one plant from observation of a quite differ- ent plant. Nevertheless, it is of interest to observe certain analogies between the wheat grains as studied by Professor Biffen and cer- tain of our plant development already cited. In particular we may note that red grain is dominant to white grain, suggesting what we have said as to the dominance of black black- berries over white blackberries. Again, the rough leaf surface and bristly stem of the wheat proved dominant to the smooth leaf and smooth stem, suggesting the case of our thorny-stemmed briers in which the thorns proved dominant to smoothness of stem. But doubtless the most important revelation made by Professor Biffen's investigation was the WHEAT, OATS, BARLEY 11 fact that susceptibility to rust was dominant to immunity to rust. This means that when a susceptible type of wheat is crossed with an immune one, all the off- spring will be susceptible. But it means also that the recessive quality of immunity will reappear in one-fourth of the offspring of the second generation. And thereby hangs the tale of Professor Biffen's achievement, as will appear in a moment. CHARACTERS THAT Do NOT "MENDELIZE" Before following this let us glance at the other groups of unit characters which Professor Biff en found not subject clearly to the rules of dominance and recessiveness. These groups include fewer characters than those in the dominant list, partly perhaps because it is obviously more difficult to study characters that do not show the clear phenomena of dominance and recessiveness. But these groups are highly interesting none the less. The unit characters that showed what Professor Biffen speaks of as irregular dominance as studied in this investigation, were only two, namely: (1) felted glumes versus glabrous glumes; and (2) gray-colored glumes versus red or white glumes. 12 LUTHER BURBANK The glume, perhaps it should be explained, is a bract that has no particular interest for any- one except the botanist, but which may serve admirably in checking the results of experi- mental breeding. The glumes have practical significance for the agriculturist, because their character determines to some extent the readi- ness with which the grain is shelled out in the thresher. The interest in the different types of glumes as to smoothness and of color, in the present con- nection, centers about the fact that neither parent showed dominance in the first generation of the hybrid, the individual hybrids differing indefinitely. In some cases there would be almost pure dominance; in others a blend of the characters. But in the second generation the characters were segregated just as if they had shown the typical phenomena of dominance and recessiveness in the first generation. The third group of characters, in which there was uniform blending in the first generation of hybrids, with no tendency whatever to mani- festation of dominance of one character over the other, found representation in the following pairs of unit characters: (1) lax ears versus tense ears; (2) large glumes versus small WHEAT, OATS, BARLEY 13 glumes; (3) long grains versus short grains; (4) early habit of ripening versus late habit of ripening. As to each of these pairs of characters, the hybrids of the first generation were intermediate between the parents. For example, if a wheat having long grains was crossed with one having short grains, the hybrid bore wheat neither long nor short but intermediate; and if a wheat that ripened early was crossed with one that ripened late, the hybrid offspring ripened their grain at an intermediate season, later than their early parent but earlier than their late one. Yet here again — and this perhaps is most significant of all — there was segregation of char- acters in the second generation along the usual Mendelian lines. That is to say, the first gen- eration hybrids that bore grain of medium length will produce offspring one-fourth of which bear long grain and one-fourth short grain, the other half bearing intermediate grain; and similarly the first generation hybrids that ripened their grain at an intermediate season, pro- duce progeny one- fourth of which ripened their grain early and one-fourth late, the other half ripening their grain at the intermediate season. The importance of this observation is that it shows that the Mendelian principle of the segre- RESULTS OF WHEAT EXPERIMENTS A sample cluster of varying wheat heads from the garden in wheat experi- ments were made one summer. A glance shows the extraordinary range of variation among these crossbred wheats. Here are differences that sug- gest the possibility of developing any number of new varieties. WHEAT, OATS, BARLEY 15 gation and recombination of unit characters in second generation hybrids follows the same rule whether or not the characters show clear dom- inance in the first generation. And if we look a little beneath the surface it will appear that there are hundreds or perhaps thousands of unit characters that for one reason or another do not show the phenomena of dom- inance in the first generation and hence are exceedingly difficult to trace, and yet which reappear segregated in new and varied combina- tions in the second generation, thus accounting for the extraordinary diversity of second genera- tion hybrids to which our attention has been called again and again. It is interesting to note that Professor Bifferi found such conspicuous conditions as long grain apd short grain to fail to manifest the phenom- ena of dominance and recessiveness. Considering that tallness of vine had shown itself to be dominant over shortness of vine in Mendelian peas, it might perhaps have been ex- pected, reasoning from analogy, that long grains of wheat would be dominant to short grains, But I have already suggested that it is unwise, to attempt to predict the hereditary tendencies of one plant from observation of another; and in particular it should be said that the stems of 16 LUTHER BURBANK plants, as regards their fixity of hereditary tend- ency, are likely to be on a different plane from the flowers or fruit, or any other new characters. The particular arrangement of floral envelope that characterizes the plant of to-day is of rela- tively recent development, and may be expected to be subject to greater fluctuations, or, in other words, to show greater plasticity under the dis- turbing influences of hybridization. Professor Biffen even found that there was a difference in the manifestation of dominance and recessive- ness with regard to certain characteristics between different varieties of wheat. Thus, in the matter of the glumes, where the parent that bore a felted glume was the variety known as "rough chaff," the felted glume proved dominant over the smooth glume. But where the felted parent was the variety known as rivet wheat, the phenomena of dominance was irregu- larly manifested, or manifested not at all. So hybrids of the rivet wheat were listed in the class of irregular dominants, as above outlined. PRACTICAL APPLICATION OF THE NEW KNOWLEDGE Having thus analyzed his wheat plants and made himself familiar with their hereditary pos- sibilities, Professor Biffen was ready to make WHEAT, OATS, BARLEY 17 application of his knowledge to the improvement of existing varieties of wheat. In particular he desired to produce a variety of wheat that would be immune to rust, yet would at the same time produce a good head of wheat having the quality described by the miller as "hardness" — a quality that is essen- tial to the making of high-grade flour, yet which some otherwise excellent wheats alto- gether lack. Material was at hand for crossing experiments in that there was a race of wheat known to be immune to the yellow rust which had not hitherto been thought of as solving the rust problem because it bore grain of very poor quality. To Professor Biffen, armed with his new knowledge, it appeared that it should be possible to combine this immune wheat of poor quality with susceptible races of wheat bearing a good grain in such a way as to secure a new race that would present the good qualities of each parent and eliminate the bad qualities. So he crossed a race of wheat that bore a grain susceptible to rust with the immune variety that bore the grain of poor quality, and developed a generation of crossbreds all of which were — quite as he had expected — susceptible to the attacks of the rust. A SHEAF OF OATS Two of my new oats, also, are taking their place as best. One of these is a giant- growing kind, the other a new, fat, productive, hull-less oat. WHEAT, OATS, BARLEY 19 To the untrained plant experimenter it would have appeared that this experiment should be carried no further. Progress was apparently being made in the wrong direction; for whereas half the parents were immune to rust, all of the children were susceptible. But Professor Biffen knew, as we have already seen, that susceptibility and immunity constituted a Mendelian pair of hereditary fac- tors. So he knew that in the next generation one-fourth of the hybrid plants would be immune to rust. And this expectation was justified by results. The second generation hybrids showed diverse combinations of various other qualities that were under consideration, and a certain pro- portion of them revealed the combination of the desired quality of grain with the stems immune to the attacks of the rust fungus. As immunity to rust is a recessive factor, it follows that the second generation hybrids that show such immunity will breed true to that char- acter. Their offspring will be immune. But as regards certain other qualities, notably hardness, it was necessary to continue the experiment through a third generation, in order to discover which of the plants that were individually hard were pure dominants as regards the quality of hardness. 20 LUTHER BURBANK To ascertain this it was necessary only to plant the grains showing the desired quality in plots by themselves. The individuals that produced only hard- grained offspring in the next generation were thus shown to be pure dominants for that quality. They constituted a fixed race and could be depended upon to breed absolutely true. Thus the clear recognition of the qualities of Mendelian segregation, as applied to the differ- ent pairs of unit characters representing respec- tively desirable and undesirable qualities of the wheat, enabled Professor Biffen to produce in the third generation a fixed race of wheat having the desired qualities of grain and a plant stem that is immune to the yellow rust. The seeds of this new variety being multiplied as rapidly as possible, a wheat was produced that promises to be of enormous importance to the grain growers of England. It is obvious that a similar line of experiment should enable the plant developers of other coun- tries to produce new varieties of wheat that will be immune to the various rusts, and thus to rid the agriculturist of one of the pests that of all others has hitherto rendered his calling precarious. WHEAT, OATS, BARLEY 21 POSSIBLE AID FROM THE WILD WHEAT My own extensive and very expensive experi- ments with wheat and other grains have been carried on for many years and the results, though not very profitable to myself financially, have proved, even at this early date, that they will add many millions of bushels of far better grains not only to the American farmer, but also to the growers of other countries where they are now rapidly supplanting other grains for resistance to rust and in larger, whiter, and harder kernels and ability to stand up where other grains fall during storms. And better yet, by analysis, as well as by baking test my "Quality" wheat stands at the apex, and the improvement in other grains is now being fully appreciated by growers in both hemispheres. All my experiments, of every nature, have been carried on for fifty years without any outside aid from any source, except the welcome given them by growers and the sums received from them as they have been from time to time introduced. Much further investigation will be needed before we can make sure as to the material that is available. But peculiar interest attaches to the investigations recently made by Mr. O. F. Cook, the biometrist in charge of crop acclima- SAMPLE HYBRID SUNFLOWER Interesting and beautiful hybrids are quite readily produced, and these variations are fixed so that they may be depended upon to come true from seed with attention to keeping the new varieties from crossing with others, and a careful weeding out of those not coming strictly up to the new standard. WHEAT, OATS, BARLEY 23 tization and adaptation of the U. S. Department of Agriculture, with reference to the wild wheats of Palestine, which were discovered by Mr. Arronson, a native of Palestine. Mr. Cook's reseaches have shown that there are races of wheat growing wild in southwest- ern Asia that are prototypes of the cultivated wheat. The resemblance of these wild forms to the cultivated varieties is striking. Yet the dif- ferences are also very conspicuous. The wild wheat has a looser, less compact head, and some varieties have the peculiarity of shedding the spikelets that hold the grain individually, each spikelet being provided with a barbed shaft which serves the purpose of helping the grain to attach itself or even to bury itself in the soil. All of which would be expected in a wild wheat, which is found also in the wild oats and rye as well as in rice. The kernels of these wild wheats are not large, but some of them are of more or less edible quality. A chief interest in the plant centers about its seeming immunity to rust. And the question at once arises as to whether it may not be possible to hybridize these wild wheats with the culti- vated ones to secure resistance to disease as well as unusual variation, vigor, and hardiness. 24 LUTHER BURBANK Tests calculated to discover possibilities in this direction are now being made, and there is some reason to hope that they will have valuable results. It may be added that the wild wheat is not universally self-fertilized. The stamens and pis- tils of its flowers sometimes protrude and permit cross-fertilization by the aid of the wind or in- sects. This may to some extent facilitate the hybridizing of the wild wheat with cultivated wheats. But, on the other hand, it will probably be desirable to eliminate this propensity from the new varieties after they are fixed for commercial use. For, as already pointed out, there are great advantages in the self-fertilization of a grain like wheat, to prevent deterioration of the type by undesired crossing. But the question of the hybridizing of the domesticated wheat with the wild type remains for future investigation. As I have already pointed out, this work is preeminently one that should go forward under Government auspices. My own experiments in this line with the wild wheats are necessarily limited. A work that involves matters of such vast economic significance, having direct connection WHEAT, OATS, BARLEY 25 with the cost of living as applied to every mem- ber of the community, should not be hampered by any financial restrictions, and should have the cooperation of investigators in many parts of the world; such cooperation as a government bureau alone can command. The little company of grasses, represented by wheat, rice, barley, rye, and oats, have since prehis- toric times occupied a preeminent position in supplying man and his domesticated animals with suitable foods. FOOD FOR LIVE STOCK SOME SUGGESTIONS ON CLOVER, TIMOTHY, AND ALFALFA FORTY million acres devoted to it; an annual crop of seventy million tons, valued at something like three-quarters of a billion dollars. Such is the record of hay in the United States. And of course this takes no account of the other millions of acres that are devoted to pas- turage, much of which would be hay if it were not harvested directly by browsing live stock. Just how much this would add to the value of the crop it is difficult to say. But without at- tempting an exact computation, it will be clear that the value of the forage crops in America reaches a colossal figure. There are many kinds of grass that may be found first and last in pasture and hayfield, but the one grass that overshadows most others, especially in the Eastern States, because of its universal popularity is that known as timothy 27 S8 LUTHER BURBANK in most regions, and in some regions as herd's grass (Phleum pratense). It may be of interest to recall that each name is merely borrowed from the name of the man who was instrumental in introducing this partic- ular grass; one man being Timothy Hanson or Hanse, of Maryland, who is said to have brought the seed from England in 1720; the other being John Herd, who is alleged to have found the grass growing wild in a swamp in New Hamp- shire as early as 1700. One of these men distributed the grass through Virginia and Carolina, the other through New England and New York. From these regions it has spread in every direction, proving adaptable to all climates and soils, until it assumes preeminence in the pas- ture and hayfield quite unchallenged except by members of the clover family, with which it is often associated. The clovers, to be sure, are not grasses in the technical sense of the word. Nor, indeed, have they the appearance of grasses even to the eye of the most casual observer. But they rival the grasses in their importance as fodder plants. In certain regards, as for instance in the amount of protein they bear, they outrival the grasses. Also in their capacity to produce successive crops FOOD FOR LIVE STOCK 29 in the same season, some of the clovers, notably the more recently introduced alfalfa, are supe- rior to the grasses proper. But in general clover and timothy are mixed to form the hay crop, the clover growing densely near the ground, and the timothy rising above it, and the two making a blend that is found exceed- ingly palatable by all herbivorous animals. The fragrance of new-mown hay suggests palatability to the human senses as well, and even though the hay crop furnishes food for man only at second hand, no one would be likely to question its wholesomeness. IMPROVING THE CLOVERS There are certain of the clovers, nevertheless, that have a poisonous principle. Notable among these is a form of sweet clover not distantly re- lated to the alfalfa, which grows in some of the States of the Middle West and produces an enormous crop which would have great value were it not that unfortunately the tissues of the plant contain a considerable percentage of a bitter alkaloid called brucine, which is highly, poisonous, being closely related to the well- known drug strychnine. A few years ago I received from Kansas seeds of this plant, with the request that I develop 30 LUTHER BURBANK from it a variety in which the brucine is reduced to a minimum, or, if possible, wholly removed. The seeds received were of various colors. My first move was to have the seeds sorted, placing white ones, black ones, and green and brown by themselves. They were then planted in separate lots; a fifth lot being reserved for a mixture of the seeds of uncertian shades. Thus it was possible at the outset to determine whether the production of plants having a large brucine content was associated with any particular color of seeds. Should such be found to be the case, the experiment would obviously be shortened, as only the plant bearing the mini- mum amount of brucine would be used for fur- ther testing. Experiments showed that the plants from the white seed apparently contained an appreciably less quantity of brucine than the black ones. As an additional element in the selection, I chose, as is my custom, the seed plants that started very early in the spring. From among these the next selection was made of the plants that had broad foliage and continued to make a very strong growth. Thu& several objects were attained almost from the outset. A second se- lection along the same lines showed that some plants have a much smaller brucine content than FOOD FOR 1.IVE STOCK 31 others, and that it will be quite possible to sepa- rate these and thus produce a variety relatively free from poison. Some similar experiments in improving peas, beans, and other plants related to the clovers, gave full assurance that I should be successful in the present instance, merely by selective breeding, in producing a plant with relatively low brucine content, and the experiments even in their initial stages justify this belief. Whether it may be necessary to resort to hybridizing experiments in order to eliminate the brucine altogether or to reduce it to a negligible minimum, remains to be seen. These experiments were begun only in 1910. It should be explained that the hybridizing of the plants of this group is relatively difficult, because the flowers are incased in a closed re- ceptacle, as with peas and beans, which belong to the same family with the clovers. All of these so-called leguminous plants — and they are outnumbered only by the composite flowers — bear the stamens and pistils thus guarded, and are normally self-fertilized. As already pointed out, this makes the experi- ment of hand-pollenizing these plants a rather tedious one. In the case of the clovers, the flowers being very small, it becomes a somewhat 32 LUTHER BURBANK delicate operation as well. But the later stages of the experiment are greatly facilitated by the fact that the flowers are self -fertilized. With these plants, as well as with small grains, this becomes an important aid in fixing a type, and in maintaining a pure race once it has been developed. For the most part my experiments with the clovers have been made through selection and without resort to hybridization. But in excep- tional cases I have cross-pollinated these plants, to test the possibilities of work in this line. I found that the process involves no great difficul- ties notwithstanding the small size of the flowers. In practice I found it better to remove all but two or three flowers in a clover head. The remaining ones have the petals and the stamens removed with a small pair of forceps, after which the application of pollen from another clover head presents no special difficul- ties ; care being taken, of course, to see that the pistil is at the right stage of development. DEVELOPING NEW CHARACTERISTICS OF STEM AND LEAF In the course of these experiments I have grown in the neighborhood of two hundred species of clover. Many of these are native 1— Vol. 6 Bur. FOOD FOR LIVE STOCK 33 species, some of which invaded my grounds unasked. Others have been received from far- away regions, in particular from Peru, Bolivia, and Chile. Whereas the white clover in its common na- tive forms is a relatively small plant, dwarfed besides the red crimson clovers, there are South American species or subspecies that are of rela- tively gigantic growth. One of these that I received from South America was a seeming "sport" — possibly due to an accidental hybridiz- ing with some other species — that grew several times as fast as any of the others in a lot of seedlings. A single plant of this giant variety would spread from four to six feet, the foliage being proportionately enlarged, while a neighboring plant would perhaps grow ten to fifteen inches. Selection among these rapid growers enabled me to develop several varieties that had the char- acteristic of growing to quite uncloverlike size. But there is no sale for new clovers unless the seed can be furnished by the ton, and as I had no opportunity to produce seed on a large scale, the giant races were ignored, when they had ceased to interest me from an experimental standpoint. For a number of years I worked also upon a clover that, without having exceptional qualities 2 — Vol. 6 Bur. 34 LUTHER BURBANK of stem, produced a very large foliage. In this case also the development was made solely by selection, the largest leafed individuals of a fraternity being selected for preservation gen- eration after generation. In the same way I produced a five-leafed strain of clover from a sport that appeared among plants of the usual three-leafed type of white Dutch clover (Trifolium re pens). The four-leafed clover is of course well- known as an occasional sport. A five-leafed clover will appear in a lot of seedlings now and again, and there will be found a few five-leafed individuals among the plants grown from seed of this sport. It would, however, require many repetitions seemingly to fix a five-leafed race, the tendency to reversion to the familiar three- leafed type being of course very pronounced. Another anomaly consisted of a clover with leaves beautifully colored — variegated in black, brown, crimson, scarlet, yellow, white, and green, in different forms and figures, no two plants being closely similar in the coloring of the leaves. This plant was introduced as a new ornamental variety, but as the original plant came from a warmer climate it did not thrive in the Eastern States and has probably been allowed to die out altogether. I have another stock of this FOOD FOR LIVE STOCK 35 which came from chance seedlings, but in no respect equal to the well-bred type formerly possessed. One of the clovers found on my Sebastopol farm has the color intensified to a bright, rich crimson, which has been reproduced exactly from seed. This is probably a species introduced from South America. A very marked tendency to variation is shown by a large number of clovers when brought to California from distant regions. THE COMING OF ALFALFA Doubtless the most important of the clover importations is the plant that has become famil- iar as alfalfa (Medicago sativa). This is a form of clover, of which there are several species and almost innumerable varieties, that is adaptable to relatively arid regions, inas- much as it sends its roots to a depth of sometimes ten or even fifteen feet in search of moisture and nutriment. Such a plant, once it has attained a fair growth, is almost independent of the rain- fall for months together. Moreover, the vigor of root of the alfalfa is duplicated by the comple- mentary growth of its foliage, which develops so rapidly and so persistently that it may be cut three, four, and even five times in the season, depending upon climate. 36 LUTHER BURBANK The enormous productivity of alfalfa, together with its adaptability to arid regions, led to glow- ing predictions as to the importance of this new forage crop, when it was first introduced years ago. In the southwestern part of the country the predictions have been more than justified, but alfalfa for a time failed to make its way in the Eastern and Northern States as rapidly as had been expected. The principal reason for this is that our most common alfalfa was brought from Peru or Bolivia. Had the plant come from Patagonia or southern Chile instead, or from Russia, its original home, being therefore represented by hardier varieties, it would probably have spread all over the Eastern States and have added vastly to the value of the forage crop everywhere. But now hardier types of alfalfa are making their way to the North, and even into Canada, and possibly selective breeding will develop races more resistant to frost than any that have hitherto been imported. A form known as Turkestan alfalfa has lately been introduced that is recommended for its hardiness. When grown side by side with the ordinary alfalfa on my place, it is difficult to distinguish the two plants. But the Turkestan variety may of course have qualities of hardiness FOOD FOR LIVE STOCK 37 that are not revealed in its appearance. There are other strains being grown that are said to be even more hardy. The alfalfa has so recently been introduced that it has not been very extensively experi- mented upon. There is no plant, however, which can be taken up for development to better advan- tage by the Government than this thrifty and drought-resisting clover. With this plant, as with the cereals, work should be carried out on an extensive scale by some one who has oppor- tunity to test the plants in a comprehensive way. As already noted, it is useless to develop a small quantity of seed of a new variety, as the practical stock raiser will not be interested in the seed until it can be offered by the ton. SOME OTHER CLOVERS I have received a large number of alfalfas and clovers from the mountains and plains of Chile, and have been struck with the close similarity between some of these and the clovers that have invaded my gardens. Others, however, are indi- vidual in appearance and differ markedly from any that I have seen elsewhere. Among the Chilean clovers that I am now testing is one that is a giant in its proportions as to leaves, foliage, growth, and blossoms. 38 LUTHER BURBANK Another of the Chilean clovers has a heart- shaped brown spot on the leaf. The bloom and seed of this variety closely resemble the common bur clover, but the leaves are several times as large as those of that plant. The bur clover (Medicago denticulata) is of peculiar interest because it produces enormous quantities of seed that fall from the stalks when ripe, and in our dry climate may remain edible for some months. The plant was at first thought to be a nuisance, but its value in a region where there is no rain for months together soon came to be recognized. To anyone who is not acquainted with the bur clover it is matter for astonishment to see a herd of sheep, cattle, or horses, or a drove of hogs pastured in a field where there is not a vestige of green herbage; and yet to note that these animals are well-conditioned and even fat. They feed on the bur clover seed, the pods of which sometimes cover the ground half an inch or more in depth. The plant itself has withered and disappeared, but the seed-bearing pods furnish a forage crop that has no substitute in this region, although it would probably be unsuited to the East. The bur clover has a small leaf and small blossoms. It runs and spreads by long, wiry, FOOD FOR LIVE STOCK 39 slender stalks, and does not stand upright, so that it could never be profitably cut for hay, making only a tangle of tough threadlike stalks. Yet its peculiar property of producing an abun- dant crop of pods makes it in some localities quite as valuable a pasture plant as the common red clover is in the East. Neither the crimson clover (Trifolium incar- natum) nor the common red clover is extensively grown on the Pacific Coast. White clover is cultivated for lawns, mostly in combination with blue grass. It will often cover a bare spot under a tree where the blue grass does not thrive. Alsike clover (T. hybridum) is another form that is seldom seen in California, partly perhaps because it does not tend to send its roots deeply into the soil, and hence is not as well adapted to a dry climate as are the alfalfas. On the other hand, it thrives on a clay soil, and in regions to which it is adapted it is a valuable product. There are numerous other species of clover that have as yet been almost neglected by the plant developer, which offer inviting oppor- tunities. Even without hybridization, plants grown from a given lot of seed will vary greatly. Selec- tion among the most familiar races of clovers would readily result in the development of 40 LUTHER BURBANK new varieties that might be of enormous value. The fact that the plant thrives more or less under disadvantageous surroundings has partly accounted, no doubt, for its neglect by the plant developer. But now that year by year there is a growing recognition of the need of intensive cultivation of farm crops, the clovers are sure to come in for a larger share of attention. Other leguminous plants, including the peas and beans as well as the clovers, have long been known to be characterized by the unusual amount of their protein or nitrogenous content. THE FOOD VALUE OF CLOVER This has led the plant physiologist to regard the clovers as having an exceptionally high food value. As compared with timothy grass, for example, clover contains, pound for pound, a very much larger amount of nitrogen. As nitro- genous foods are the muscle builders, the value of this is obvious. There has been a tendency in recent years, to be sure, to question whether the nitrogen content has quite the significance that was formerly ascribed to it. It has been pointed out that horses do not need a very large amount of pro- tein foods unless they are exercising actively, and that in this event they usually secure an FOOD FOR LIVE STOCK 41 adequate amount of protein in the grains, chiefly oats, that are fed them. Cattle that are being fattened may thrive as well on foods that are less rich in protein. Milch cattle, and growing cattle, on the other hand, need a nitrogenous diet. And, indeed, all along the line, it is not to be denied that a protein food has exceptional nutritive value. It is partly at least with this in mind that the intelligent agriculturist mixes clover with the timothy in his pastures and in his hayfield. At least a partial explanation of the high nitro- gen content of the leguminous plants has been furnished by the discovery that these plants have the very unusual capacity to extract nitrogen from the air. Most plants, as we have seen, are ' quite powerless to take even the most infinitesimal quantity of nitrogen from the air, and would starve to death for lack of nitrogen even while their tissues are perpetually bathed in it — as the tissues of all aerial plants necessarily are — inas- much as the atmosphere contains nitrogen as its most abundant element. But the leguminous plants are able to extract nitrogen from the air directly; not, however, with the aid of their leaves or stems, but only by way of the roots, and there only with the aid of the little tubercles that develop under the influence 42 LUTHER BURBANK of microorganisms. It is, indeed, the micro- organism that extracts and fixes nitrogen and makes it assimilable for the plant. The tissues of the plant itself have no direct share in the work, beyond giving hospitable refuge to the microorganisms themselves. The little tubercles that form on the clovers and the allied plants vary in size and shape with the species of plant, although the microorganisms that produce the tubercles and that assist the plant in securing a supply of nitrogen are closely related. There are, however, different groups of microorganisms that are able to produce the tubercles and help in nitrogen fixation. As microorganisms are not always present in any given soil, it has been found sometimes de- sirable to inoculate the soil in which various clovers are to be grown. This may be done by scattering over the field soil from a field in which tubercle-bearing plants of the same species have been grown the previous year. It has been clearly demonstrated that such in- oculation of the soil may lead to much freer growth of tubercles than would otherwise take place, and to the increased vigor and growth of the clover crop. The use of artificial cultures of nitrifying bacilli has also been recommended. It FOOD FOR LIVE STOCK 43 is necessary, however, to treat the solution in a particular way in order to insure that the micro- organisms may maintain vitality. If they are dried slowly under the usual atmospheric condi- tions, the microbes die. It has been found possible to preserve them by rapid drying of pieces of cotton dipped in a solu- tion containing the microbese The Department of Agriculture at Washing- ton has experimented with a method of distrib- uting liquid cultures in glass tubes. Special packages of minerals, including phosphate of potassium, sulphate of magnesium, and ammo- nium phosphate, are sent with the culture tube to make a nutrient medium in which the culture may be developed. The clover seeds are moistened with this liquid culture, dried rapidly, and sown as quickly as practicable. Another method is to sprinkle the liquid on a portion of soil and scatter this over the land. This inoculation of the soil with the nitrogen- fixing microbes constitutes a new departure in agriculture that would have been quite incom- prehensible to anyone before the day of the modern bacteriologist. But so much has been learned in recent years about the bacteria and their almost universal prevalence and share in the 44 LUTHER BURBANK vital activities of animals and plants that the sprinkling of the soil with bacteria seems almost as commonplace a deed as the sowing of seed. This method, however, is obviously only an accessory to the methods of the plant developer. It has exceptional interest as illustrating the application of science to the art of agriculture, but it has no direct association with the work of the experimenter who develops plants by hybrid- izing and selection. Just how the leguminous plants came to de- Jvelop this anomalous habit of serving as hosts for the particular types of bacteria that can aid them by the extraction of nitrogen from the air, it is difficult to understand. But the fact that they have developed the habit is of very great im- portance, because it enables these plants to enrich the nitrogen content of the soil in which they grow, instead of impoverishing it. By turning the clover under with a plow, the farmer is enabled to restore to the soil an equiva- lent of the nitrogen that was taken from it in a preceding season by other crops. The importance of this will be obvious to any- one who is aware that nitrogen is an absolute essential as a constituent of a soil on which good crops of any cultivated plant are to be grown, and who further understands that the available FOOD FOR LIVE STOCK 45 supply of nitrogenous salts with which a depleted soil may be restored has until recently been very limited. Some readers may recall the prediction made not many years ago by the English chemist, Sir William Crookes, to the effect that the world would presently suffer from a nitrogen famine that would greatly reduce the wheat crop, and perhaps subject the entire race to danger of star- vation. At that time the chief supply of nitrates came from the nitrate beds of Chile; and it had been estimated that in less than twenty years these beds would be exhausted. No one then could say just how the need of the agriculturist would subsequently be met. But the discovery that leguminous plants extract nitrogen from the air gave partial answer. And almost simultaneously a more complete answer was supplied by scientific workers, headed by the Swedish chemist, Professor Christian Birkeland, in association with a practical engi- neer, Mr. S. Eyde, who discovered that it is pos- sible to convert atmospheric nitrogen into nitric acid with the aid of electricity. Another method of fixing atmospheric nitro- gen was soon afterward developed in Italy. Thus the inexhaustible sources of the atmosphere were made available. So there is no longer any 46 LUTHER BURBANK danger of a nitrogen famine, and the developer of plants no less than the consumer of plant prod- ucts may look forward without apprehension, so far as the danger of the starvation of plants for lack of nitrogen is concerned. But the mechanical processes of nitrogen fix- ation are necessarily expensive, and the aid of the clovers and their allies will no doubt continue to be sought for a long time to come by the agriculturist who wishes to restore nitrogen to his fields in the most economical manner. The first crop of clover is usually cut for hay, and a second crop used to turn under in the fall to fertilize the soil. Thus this plant occupies a unique place among farm products. It not only supplies a valuable forage food, but it also helps the farmer to keep his land in a condition of perennial fertility. There is nitrogen, worth millions of dollars, in the air over every farm in America — and by the simple process of raising inoculated legumes, we can extract and em- ploy it — not only without expense, but at the same time producing crops of unusual profit. A RICH FIELD FOR WORK IN THE TEXTILE PLANTS IMPROVING THE FIBERS OF FLAX, HEMP, AND COTTON THE cultivation of flax in America gives a very striking illustration of the extrava- gance of our agricultural methods. Something like two and a quarter million acres of land are given over to the cultivation of flax, the harvested product being about twenty-five million bushels of seed. But the stalks of the plants covering this vast acreage are for the most part regarded as waste material, notwithstanding the fact that the fiber of the flax plant is every- where recognized as the most aristocratic of vegetable textile materials. Flax fiber, the material from which linen is made, bears somewhat the same relation to cotton fiber that silk bears to wool. Unfortunately, the plant that bears good seed does not make good fiber ; although it can be used as a second quality flax, and has been used as stock for paper. 47 48 LUTHER BURBANK Flax in America is usually grown for the seed only, as the high cost of labor makes competition with the foreign product difficult. Contrariwise the hemp plant (Cannahis saliva) , a plant belonging to the mulberry family and distantly related to the hop, which resembles the flax only in the fact that it produces a tough and resistant fiber that may be used for textile purposes, is cultivated in this country exclusively for the fiber, its seed being almost altogether neglected. Yet the seed of this plant is prized in other countries for its oil, and its neglect here illustrates the same principle of wasteful use of our agricultural resources. Hemp, however, is not very extensively grown, being chiefly confined to regions of the blue-grass country centering about Kentucky and Tennes- see. Its fiber is coarse, and is used chiefly for making cordage and warp for carpets. At best the cultivation of hemp does not constitute an important industry in the general scale of American agriculture. COTTON FOR SEED AND FIBER But when we turn to the third textile plant, cotton, we have to do with an industry that ranks second only to the cultivation of Indian corn. THE TEXTILE PLANTS 49 And here there is a story of waste that assumes more significant proportions. For the cotton plant also produces seeds as well as fiber; and it is only in comparatively recent years that these seeds have been regarded as other than a waste product the handling of which gave great an- noyance. Fortunately, however, this has been changed in recent decades, and the cotton grower now understands that the seed of the plant is a prod- uct quite rivaling in importance the coveted fiber itself. Not only does the seed contain an oil that when pressed out makes a very palatable substi- tute for the oil of the olive, but the residue con- stitutes cattle food that sells for from fifteen to twenty dollars a ton — a residue that until recently was used only as fuel, until its value for starch was discovered. So the cotton plant takes high place among producers of commercial seeds, quite aside from its significance as a producer of the most beauti- ful, useful, and abundant textile fibers. In the present connection, however, it is the quality of the cotton as a producer of textiles rather than as a producer of seeds that chiefly claims attention. The importance of the plant as a producer of fiber is too well known to require extended com- THE FLAX PLANT In this country, flax is grown quite extensively, but almost exclusively for the seed, the stalks being regarded as waste material. Our new giant white- seeded flax, which makes a white oil, is a wonderful improvement. THE TEXTILE PLANTS 51 ment. Suffice it that America now produces not far from three-quarters of the world's total cotton crop, the land devoted to this crop aggre- gating more than twenty-five million acres, and the annual yield averaging something like twelve million bales, with a value of much more than half a billion dollars. It is obvious that a plant that has such com- mercial importance is one that beckons the plant developer. For even slight improvements, when applied on so magnificent a scale, may have vast significance. CULTIVATION AND IMPROVEMENTS Some very good work has been done in the improvement of the cotton by selection, without the aid of hybridizing. The cotton plant came originally from the Orient, having been cultivated in India from time immemorial. It belongs to a large family that includes the hibiscus, bearing beautiful flowers, and the vegetable called, in the South, Gumbo. The Egyptian and Peruvian cotton and Sea Island cotton falls into one group and the American upland cotton and Indian cotton into another. It is doubted, however, whether the wild prototypes of the cultivated species are known. 52 LUTHER BURBANK The newer classifications recognize twenty- four species or subspecies of cotton, including a number of American varieties that have attained great commercial importance. The American upland cotton is a perennial plant, now cultivated as an annual, that had its original home somewhere in the heart of South America, but which has proved adapted to the climate of the North American cotton belt, and is now the chief producer of cotton in America, and hence in the world. Sea Island cotton is a species indigenous to the West Indies. It is of larger growth than the upland cotton, attaining a height of three to eight feet, and the bolls that contain the cotton fiber are sharp-pointed and characterized by having only three instead of four or five divisions or locks. Sea Island cotton yields less fiber per acre and is more costly to pick and gin than upland cotton. But it commands a higher price. It is grown chiefly on islands, and along the coast of South Carolina and Georgia. It has peculiar value as material for the making of the founda- tion for automobile tires. The Indian cotton and the Egyptian are not grown extensively in this country, although varieties have been introduced and grown by the United States Bureau of Plant Industry for ex- THE TEXTILE PLANTS 53 perimental purposes. It is probable that these species will prove valuable when the method of hybridization is applied to the development of new races of cotton modified to meet special needs. The cotton has a large, attractive flower, and cross-fertilization occurs to a considerable extent through the agency of bees and other insects. There is no difficulty in hybridizing different species. On the contrary, it is difficult to prevent cross-pollination where different kinds of cotton grow in the same vicinity. There is danger of contamination of the strain of any particular cotton in this way. But, on the other hand, there is always the possibility of the production of new and important varieties through such crossing. IMPROVEMENT THROUGH SELECTION Until very recently, as already intimated, the improvement in cotton has taken place almost or quite exclusively through the selection of seed, without any conscious effort on the part of the grower to predetermine the characters of the seed by cross-fertilizing the parent plants. Indeed, until somewhat recently, cotton grow- ers, in common with other agriculturists, have been more or less oblivious to the need of care in the selection of seed. And even now, accord- 54 LUTHER BURBANK ing to so good an authority as Professor Thomas F. Hunt of the New York College of Agricul- ture, probably half the cotton seed planted is taken at random from the public gin. Yet the importance of selection has come to be under- stood in recent years by many growers, and the old slipshod methods have been abandoned by such cotton raisers as appreciate the advantages of applying scientific methods to the betterment of their crop. The method that has produced excellent re- sults is one that has been illustrated over and over in connection with one after another of my ex- periments in plant development. It consists essentially in selecting for seed the product of plants that are observed to be more productive than their fellows, and which at the same time produce cotton fiber of superior quality. With cotton, as with other plants, it does not at all suffice to select merely the individual bolls that chance, through some nutritional advantage, to grow to large size. It is necessary to consider the plant itself and its total product as well as the average quality of that product. We have seen that, under precisely similar conditions, dif- ferent individual plants of every species show a more or less wide range of variation as to size and THE TEXTILE PLANTS 55 productivity, resistance to disease, and other qualities. This variation is quite as notable among cotton plants even of the most fixed varieties, as among most other cultivated plants. The practical method employed by the most intelligent cotton raisers is to send trusted em- ployees through the fields to select the plants the product of which is to be saved for seed. The seed cotton thus obtained is ginned separately, and the owner who has taken this trouble is sure to be repaid by the improved average quality of his crop the ensuing season. The United States Bureau of Industry has published details as to a method of selective breeding that has been practiced for several years by some growers of Sea Island cotton, through which the staple has been increased from 1.75 to 2.5 inches in length. The method re- quires four years of selection to secure enough seed for general planting. The first year five or more plants are selected as the best in the field. It is urged that it is important to take the seed of at least five plants, not merely of one, because an individual plant of fine appearance may fail to transmit its charac- teristics. Yet my own experience with a wide range of plants would lead me to have much 56 LUTHER BURBANK confidence in the progeny of the one best plant in the field. However, the practical cotton growers have thought that they have secured better results by selecting several plants instead of depending on a single one. The second year five hundred or more seeds are selected from each plant for the next year's planting. The second year's crop is examined with great care to see whether the desired quali- ties are being strongly transmitted. If such is the case, several of the best plants are again selected to furnish seed for a new planting. Meantime the seed of the remainder will suffice to plant a patch of about five acres in the third year. The third year five hundred or more plants will be grown of each of the individual selections, and as many five-acre seed patches to produce seed for general planting as there were indi- viduals of the first year whose progeny was considered worth propagating. In the fourth year there will be seed for gen- eral planting from the five-acre seed patches of the previous year. There will be several five-acre seed patches from the specially selected indi- viduals of the second year; and five hundred or more plants of each of the individual selections. THE TEXTILE PLANTS 57 That is to say, in this fourth year we shall have a general crop of cotton plants all of which are the descendants in the third filial generation of the five plants or thereabouts selected in the first year. And inasmuch as each successive year the five or so best plants have been selected to start a new series, the process of betterment will go on in- definitely. The general crop in each successive year will represent the progeny, not of the crop of the preceding year, but of a third generation off- shoot from the best plant of an earlier year. And the crop of this year will of course supply the five best plants to become the progenitors of the general crop four years from now. And this, it will be obvious, is merely the applying of the familiar rules of selection which we have seen illustrated in the production of specialized races of flowers and fruits, grains, grasses, and vegetables of many types. The only difference is the practical one that, in my experi- ments, the inferior members of a fraternity are usually destroyed when the best half dozen have been selected for preservation, instead of being preserved for cropping purposes. This modification obviously in nowise alters the principle, but it is a practical change that is clearly necessary to meet the needs of a cultivator COTTON FLOWER AND SEED HEAD The function of cotton fiber is, of course, to protect the seed and to facilitate its distribution. But nature would scarcely have carried the elabora- tion of the protective fiber to such a length had she not been aided by man, who has selected generation after gen- eration among the cotton plants for the ones that produced the best quality of fiber, as gauged by his own needs. THE TEXTILE PLANTS 59 who, while striving to improve his crop, must at the same time take such crop as can be grown year by year, without waiting for the best ulti- mate product. Of course there are limits to the amount ofx development that is possible through such selec- tive breeding. The plants operated with have certain heredi- tary limitations, and these are pretty surely fixed by long generations of inbreeding. When these limits are attained by the practical plant devel- oper, through the carrying out of such a system of rotation as that just outlined for a good many years, the best pure types of cotton represented in the strains under investigation will have been isolated, and the experimenter will find it diffi- cult or impossible to make further improvement by the mere process of selection. Then it will be necessary to introduce the method of hybridizing, to give new vigor to the plants and to produce new segregations and com- binations of characters that will be equivalent to the production of new varieties. And for this purpose, as I have already suggested, the com- bination of strains of the American cotton with the Oriental ones, and also, doubtless, the utiliza- tion of some hitherto neglected wild species may be expected to prove of value. 60 LUTHER BURBANK A beginning is said to have been made by H. H. Webber, through combining the fine, long, strong lint of the Sea Island cotton with the large bolls and productiveness of the upland cotton. INSECT FOES OF COTTON It goes without saying that a highly special- ized plant like the cotton, and in particular a plant growing in subtropical regions, is subject to the attacks of many insects. In fact, the distinguished entomologist, Dr. L. O. Howard, enumerates no fewer than 465 species of insects that feed upon the cotton plant. But among these there are four that are so pre- eminent in their destructiveness as to make the ravages of the others seem insignificant. These are the cutworm (Aletia argillacea), the cotton worm, the cotton boll worm (Heliothis armiger) , and the Mexican cotton boll weevil (Anthonomus grandis). The cutworms are dangerous to the young plants as to other seedlings. The cotton worm may appear in hordes, but has not been especially destructive in recent years. The cotton boll worm is an insect which, notwithstanding its name, prefers other crops, in particular maize, to cotton, so that the cotton crop may be protected from its aggression by planting a few rows of THE TEXTILE PLANTS 61 maize at intervals of twenty-five cotton rows throughout the cotton field. But the newest and most aggressive of the pests, the cotton boll weevil, is an enemy that is not so easily reckoned with. This little insect has been known a long time in Mexico as a pest that attacks and destroys the tender portion of the cotton boll itself. But it is only in recent decades that this insect has worked its way northward and into the cotton region of the United States. It must now be reckoned as one of the most destructive enemies of the cotton plant in the more southerly districts. Quite recently, however, an enemy of the boll weevil has been found in Guatemala by Mr. O. F. Cook, the botanist in charge of investigations in tropical agriculture of the Bureau of Plant) Industry. This enemy of the boll weevil is de- scribed as a large, red-brown, antlike insect. It is known to the native of Guatemala as the kelep ; entomologists describe it as the Guatemala ant, Ectatomma tuberculatum. This insect is described by Mr. Cook as strik- ingly adapted by structure and instinct for the work of protecting the cotton against the weevils. It has large jaws or mandibles that fit neatly about the weevil and hold it firmly, and a sting 62 LUTHER BURBANK that penetrates a vulnerable point in the shelly armor of the weevil. The sting paralyzes the victim, somewhat as wasps paralyze spiders and caterpillars to supply food for their young. After paralyzing the weevil with the poison injected by the sting, the kelep carries its prey to its subterranean nest to feed the larva?. The kelep does not confine its predacious attacks to the boll weevil but kills also many other insects found upon the cotton, including the larvae of boll worms and leaf worms. It has the curious habit, Mr. Cook tells us, of storing the dismembered skeletons of captured insects in special chambers of its subterranean home. Through Mr. Cook's efforts, this enemy of the boll weevil has been introduced. It has shown its ability to breed both in captivity and in the cotton fields of Texas. The insect forms colonies that are said to be even more highly developed than are the colonies of ordinary ants. New colonies are formed by a subdivision of the older com- munities, as among the honey bees, not by soli- tary females as is usual among ants. It is expected that the insects will thrive in the cotton districts, and will serve at least to keep the boll weevil in check, although it is not to be hoped, according to Mr. Cook, that it will alto- gether banish the pest; inasmuch as the weevils THE TEXTILE PLANTS 63 have not been exterminated in Guatemala, although the kelep has there imposed a very important check on their increase. It is urged, however, that additional protection from the boll weevil must be sought through such development of the cotton plant itself as will make it resistant to the attacks of the insect. The authorities of the Department of Agriculture have observed that in the cotton plants of Guate- mala, where the weevil is native, the buds do not always drop off after being penetrated, and that the young bolls continue to develop. It was found on examination that such resist- ance was due to the actual growth of new normal tissue into the cavity eaten out by the weevil larva, with the result uniformly fatal to the larva itself. It appears that the larva in its younger stages subsists entirely on the highly organized food material to be found in the pollen grains of the unopened cotton flower. The new tissue formed by a mere swelling or proliferation from the central column of the flower is watery and innutritious, and may starve the larva to death even if it does not act as a poison. Here, then, is a method by which the cotton is able to offer effective resistance to the weevil. It is suggested that if a variety of cotton could be developed in which the tendency to the growth 64 LUTHER BURBANK or proliferation of the new tissue was pro- nounced, as it is in certain individuals, the weevil might be exterminated. It is considered possible that such a variety may exist at the present time in some parts of tropical America, and that if such a resistant variety can be found, it may be possible to develop the characters in the culti- vated plant through selection. Inasmuch as individual plants show this power of resistance, there should be no difficulty in de- veloping and raising cotton plants in which this resistant quality is a uniform characteristic. The problem is obviously identical in principle with numberless other problems of plant development that have been solved in the same way. And here, also, we may reasonably assume, aid may be secured through the careful cross-pollen- izing of resistant individuals, even if no resistant species can be found with which to effect hybrid- ization. It is reported that a tree cotton indig- enous to southern Mexico is partially resistant to the weevil. It will be of interest to determine whether the peculiar characteristic as to growth of new tissue that makes the individual cotton plants resistant to the weevil constitutes a unit character that will be transmitted along Mendelian lines, compa- rable therefore to immunity and susceptibility to THE TEXTILE PLANTS 65 rust as revealed in Professor Biffen's experi- ments with wheat. Whether or not such is the case, it may be expected that the cotton plants that show resist- ance will transmit this propensity to some of their offspring. It is obvious that an investiga- tion of the hereditary tendencies of cotton in this regard, coupled with experiments looking to the improvement of the quality of the fiber itself, should have at once a high degree of interest for the plant developer and the promise of large reward to both grower and consumer. The geographical location of my experiment farms makes it difficult for me to experiment with so tender a plant. But I have thought that a somewhat extended account of the work of others in the selective breeding of this plant would be of interest, partly because it suggests such close analogies with numerous experiments already detailed. I would urge upon the attention of plant experimenters who are located within the cotton belt the possi- bility of applying the principles that we have seen outlined in many hybridizing experiments to the improvement of a plant which, despite the excellence of its product, is by no means perfect. The fundamental principles of plant develop- ment are everywhere the same, and the methods 3 — vol. 6 Bur. 66 LUTHER BURBANK that have been employed at Santa Rosa to per- fect flowers and orchard fruits and vegetables, grains, grasses, etc., may be applied with full confidence to improvement of the cotton plant. In my own studies, I have come upon a variety of cotton grown in a far northern climate, that of Korea, for ages, and as it appears to be very much hardier than any cotton heretofore known, have thought it of peculiar interest. The bolls, though produced abundantly, are small and have a short staple, growing on compact, low-bushing shrubs. This matures at Santa Rosa where other cottons seldom reach even the blossoming stage. I have sent seed of this to experimenters better located; and this unusually hardy dwarf cotton may prove of value for cross-breeding purposes. The function of cotton fiber is, of course, to protect the seed and to facilitate its distribution. But na- ture would scarcely have carried the elaboration of the protective fiber to such a length, had she not been aided by man, who has se- lected, generation after generation, among the cotton plants, the ones that produced the best quality of fiber — as gauged by his own needs. PLANTS WHICH YIELD USEFUL CHEMICAL SUBSTANCES SOME OBSERVATIONS OF SUGAR CANE, HOPS, AND SUGAR BEETS AT English physician residing in Trinidad made a casual observation that proved enormously important to the growers of sugar cane. The physician observed that in the cane fields there were little grasslike plants coming up here and there. The planters whom he asked about it said that it was "grass," and let the matter go at that. But the physician had a suspicion that each blade of grass was really the shoot of a seedling sugar cane plant. As it chanced, both the planters and the physi- cian were right. The little shoots were young sugar cane plants; but of course sugar cane is • itself a giant grass, so there was no mistake. But the planters had not a suspicion as to what kind of grass the shoots were ; so when the physi- 67 68 LUTHER BURBANK cian took some of them up and cultivated them, and they were seen to develop into plants of sugar cane, everyone except the physician him- self was greatly surprised. For it had been supposed that the sugar cane does not produce seed, and such a thing as a seed- ling sugar cane was hitherto unheard of. The sugar cane belongs to that comparatively small company of cultivated plants that have almost totally given up the habit of seed produc- tion. We have seen that the horse-radish is an- other plant that has similarly stopped producing seeds, and that the common potato has almost abandoned the habit, as well as nearly all green- house plants which have been reproduced by cuttings or slips. Comment has been made, also, on the rather extraordinary character of this departure from the most sacred traditions of plant life. That an organism, whose sole purpose beyond the perpetuation of its own individual existence might be said to be the production of seed, should continue to grow and thrive and yet should totally abandon the habit of seed production seems altogether anomalous. The explanation is found, as we have seen, in the fact that man provides means for the propa- gation of horse-radish and sugar cane by division OTHER USEFUL PLANTS 69 of roots or by cuttings. In the case of the potato, nature herself has provided tubers that take the place of seeds in a measure; and we have seen that there is a curious reciprocal relation between the formation of seeds and the formation of tubers, under certain circumstances. In certain cases, for example, the growth of the roots of a plant or even of the plant stem may be promoted by the removal of the blossoms. We saw also how the potato that was grafted on the stem of a tomato might grow aerial tubers from the axils of the leaves in the position that might normally be occupied by the flowers — and ultimately by seeds, had not the potato given up the habit of seed production. Another illustration of the affinity between bulbs and flowers is shown by the onion, which sometimes grows a bulb at the top of its stalk, to perform the function of seeds in storing nutrient matter and at other times divides at the base like many other similar plants to form offshoots from which the new plant will grow another season. But in all these cases nature is substituting one means of reproduction for another, or supple- menting one means with another, and the essen- tial purpose of race preservation is not for a moment overlooked. SUGAR CANE TASSELS Notwithstanding its elaborate tassel, the sugar cane ordinarily does not bear seed. Indeed, until somewhat recently, it was not known to bear seed at all. By rare exception., however, seed is occasionally formed; and the discovery that certain little grasslike plants in a sugar cane field were really seedlings of the sugar plant led to the development of a new variety with exceptional qualities. Sugar cane had been propa- gated by division so long that it had nearly lost the power to produce seed. The sugar cane has a plume very much like that of Pampas grass. OTHER USEFUL PLANTS 71 In the case of the sugar cane, however, it might almost be said that nature has wholly abandoned the idea of provision for the multiplication of the species, and has left the matter entirely to man. For in giving up the habit of seed production, the sugar cane has developed no complementary habit of bulb production. It is propagated by cuttings, but the agency of man is necessary to place those cuttings under proper conditions for growth. Left to its own devices, the cane would be likely to give an illustration of race suicide. REJUVENATION THROUGH SEED PRODUCTION All this, however, seems out of harmony with the illustrative case with which we began. For obviously the Trinidad physician could not have found seedlings of the sugar cane unless the sugar cane produced seed. In fact, it does produce seed on very rare occasions, but the habit has been so nearly abandoned that most cultiva- tors of the plant supposed that it had been given up altogether. The Trinidad case, however, shows that nature has not altogether abandoned the sugar cane to the good graces of man. She still on occasions stimulates the plant to a revival of its long- forgot ten custom. And the benefits 72 LUTHER BURBANK that result from such revival will be obvious if we follow a little farther the story of the grass- like seedlings that the physician transplanted from the cane fields of Trinidad. It appears that one of these seedlings, grown to maturity, was carried subsequently to the Hawai- ian Islands, and there propagated in the usual way, so that in due course sufficient plants were grown from it to be tested as to their qualities of growth and sugar production. And it was soon discovered that this new seedling constituted vir- tually a new race of sugar cane ; one that would grow on land so poor that it had been allowed to remain fallow. The new variety, indeed, would produce more sugar on even the poorest land which had been abandoned than the ordinary variety produces on the best land. Being taught by this experience, the growers of sugar cane paid heed to the seedlings in fields where they appeared, and subsequently raised from seed, and distributed in all countries new varieties of sugar cane that have probably in- creased the sugar production of the world bj millions of tons each year. One could not ask a better object lesson in the possibility of rejuvenating a static race of plants through the growing of seedlings. OTHER USEFUL PLANTS 73 I first made experiments with seedling sugar cane in my own greenhouses, and when reports of these were made, received letters from the various sugar-growing regions of the world, ask- ing for further information, and now there are several well-equipped experiment stations en- gaged in the work of raising and testing sugar cane seedlings. APPLYING THE NEW KNOWLEDGE The reader will at once recall the case of the Burbank potato, which is in all respects compa- rable. There, also, a plant that ordinarily does not produce seed was found by exception to be fertile, and the plants grown from the seed showed the widest departure from the form of the parent plant, and constituted the progenitors of a new and improved variety. The obvious explanation is that the seeds owed their existence to the union of two plant strains, one represented by the staminate and the other by the pistillate flower, that must necessarily be somewhat divergent. The bringing together of the two racial strains results, as we have seen illustrated over and over, in the giving of renewed vigor or vitality to the offspring, and in the pro- duction of variation through the new assorting and recombination of characters, some of which 74 LUTHER BURBANK may have been latent and unrevealed in one or both parents. In the case of the sugar cane, propagation by cuttings had been the universal custom with the planters for no one knows how many generations. As a result, a single cultivated variety of cane that chanced to be in existence when the practice of propagation by cutting was established con- tinued unchanged as to its essential characteris- tics, and there was no apparent opportunity for any modification, except such minor ones as might result from increased or diminished nutri- tion due to the precise character of the soil and climate. But the chance finding of the seedlings put the plant on a new basis, and gave the planters new varieties that enabled them to improve the cane, and bring it more in line of competition with the rival sugar producer that had only recently come into notice, the sugar beet. At the time when the custom of propagating cane by cuttings was established this plant stood in a class quite by itself as a sugar producer. But within the past fifty years the merits of the sugar beet have come to be understood. The possibility of developing a beet with a high sugar content has been established, and the beet sugar OTHER USEFUL PLANTS 75 industry has risen to such proportions that it more than rivals the cane industry. Stimulated by this unexpected competition, which threatened to annihilate the cane sugar industry, somewhat as the work of the synthetic chemist has practically annihilated indigo grow- ing and madder growing, the planters have in recent years given serious attention to the ques- tion of the possible improvement of the sugar- producing qualities of the cane. Many experimenters from different parts of the world have written me concerning this matter within the past twenty years. And a number of my friends and acquaintances are now raising sugar cane from seed in Mexico, the Hawaiian Islands, and Cuba, with an eye to the production of improved varieties. Their efforts should be successful. Crossbreeding the sugar cane will give it new vitality, and careful selection from among the new varieties that will appear in the second gen- eration should enable the cultivators to develop new strains of the sugar-bearing cane that will be far richer in their sugar content than any of the old varieties. The cane is at best handi- capped in competition with the beet by the fact that it can be grown only in tropical and sub- tropical climates. 76 LUTHER BURBANK If it is to hold its own, it must be developed to its full possibilities of productivity. Doubtless it will be possible to develop races of sugar cane having greatly increased size of stalk, and having also a higher percentage of sugar in a given quantity of pulp. In attempt- ing such developments, the experimenters are merely bringing the sugar cane industry into line with the other great plant industries, most of which were neglected by the scientific plant de veloper until very recent years. My own experiments with the cane have not extended beyond the greenhouse, but I have found that the seed germinates readily there, although only a few seeds out of a handful may grow; the contrast in this regard being very striking with the seed of the allied Pampas grass, which is as diminutive as that of the sugar cane and not dissimilar in appearance, but which germinates promptly almost to the last seed. ALLIES OF THE SUGAR CANE I have experimented more extensively with certain relatives of the sugar cane of the tribe of sorghums. This includes not only the sorghums that produce the sirups, but also broom corn, Kaffir OTHER USEFUL PLANTS 77 corn, and a score or so of allied plants, some of which have great value as fodder plants. The best known of the sorghums shows its relationship with the sugar cane in that it pro- duces a sirup which, although not of the same chemical composition as cane sugar, is very sweet and palatable. Sorghum differs very radically on the other hand from sugar cane, in that it is a hardy an- nual plant. It came to us from China but prob- ably originally from South Africa, and it has proved adaptable to our soil and climate almost everywhere, and is grown in practically every State in the Union, for sirup making. It is known also as a forage plant of very great value, and its stalks supply fodder for the farm animals. It will be gathered from this that the sorghum is a much less specialized product than the cane, and that it retains its full vigor as a seed producer. Partly as a result of its cultivation in widely different regions of the globe, and partly no doubt through conscious and unconscious selec- tion on the part of its cultivators, sorghum has developed many varieties, which are divided into three quite distinct groups. VARIETIES OF SORGHUM This Tiardy cousin of the sugar cane is tolerably familiar in many regions of the United States. It grows far to the North, and may be cultivated like corn. Its juices differ in chemical composition from those of the sugar cane, and its product is not susceptible of refining; but it makes an excellent sirup. I OTHER USEFUL PLANTS 79 One type of sorghum is the sirup producer to which we have just referred. The other type constitutes a very valuable forage and grain-producing plant, not altogethei unlike Indian corn in general appearance, that is almost devoid of sugar. The third type resembles the others in some respects, but the kernels are smaller and more primitive in form, the plant being used for the manufacture of brooms. My own work with the sorghums has included many different varieties, but has chiefly con- cerned the nonsaccharine types, and, in partic- ular, the one known as broom corn. This is a variety of sorghum having long, slender panicles of a specialized form, pro- duced by long selection for the special purpose of making brooms and brushes. The product of this plant is familiar in every house- hold, but the plant itself has not been very generally grown in the United States until of late. There is a vast difference in the different vari- eties as well as individual plants of broom corn as regards length, strength, and symmetry of the group of panicle stems, or brush as it is technically called, and equal diversity as to the quantity produced per acre. 80 LUTHER BURBANK My experimental work with the broom corn has been directed toward the development of a long, and in particular a straight, panicle stem. Most of the broom corns have long but crooked stems — that is, stems with crooks or crinkles near the base. Moreover, most of the broom corns under cultivation vary as to the quality of the brush, some of them being long, some short, and there being a corresponding diversity as to color. I have succeeded, in a few generations of selective breeding, in greatly increasing the number of straight stems of the brush, and giv- ing them a more shapely form. Broom corn responds readily to selection and care. These experiments were made by selecting seed from the plant or plants in a lot that showed the best individual characteristics. Attention was paid not merely to the brush itself, but also to the stalks of the plant. There is obvious advantage in growing a large, long brush on a dwarfed stalk, that as little plant energy as possible may be used for the produc- tion of the stalk, the chief supply being reserved for the more important brush. It was found very difficult, but not impossible, to improve the plant along both lines simultaneously, as it seemed to be working in opposite directions. OTHER USEFUL PLANTS 81 I was also able to develop a brush that had improved qualities of firmness and durability, combined with pliable texture. The sirup-producing sorghums are chiefly of two very closely related types, which are usually spoken of as Amber and Orange sugar canes. Individual plants vary a good deal as to their sugar content and other characteristics. My experiments with the sirup producers have shown that there is a great diversity in the in- dividual plants as to the amount of saccharine substances in their tissues; and that it is pos- sible by careful and systematic selection through successive generations to increase the sugar con- tent, as has been done with the sugar beet, and is being done with the sugar cane. This work, however, has not extended beyond the experimental stages, only satisfying myself as to the feasibility of the project; it should be carried to completion by some one working under the auspices of the Government or an agricul- tural society where abundant acreage and intelli- gent help are available. The work is important, for the sirup-bearing sorghum is a plant of real value, and there is a great demand for its product. But the work of developing the plant does not offer commer- 82 LUTHER BURBANK cial inducements that make it profitable for the private investigator to devote a large amount of time to it. SOME CURIOUS CARBOHYDRATES The differences between the sweets extracted from the sugar cane and those taken from the sorghum are very obvious and tangible. One plant supplies a juice that when boiled and evaporated and refined gives a fine granular product familiar to everyone as sugar. The juice of the other plant, somewhat sim- ilarly treated, constitutes a sirup of varying color, which is exceedingly sweet and palatable, but which cannot be reduced to a granular con- dition in which it could by any chance be mis- taken for cane sugar. Yet the chemist tells us that the sugar content of the juices of these plants is in each case a compound made up ex- clusively of three elements — carbon, hydrogen, and oxygen — and that the differences observed are due to modifications in the proportions in which the different elements are compounded. It appears that sugar of the glucose type, as represented in the sirup of the sorghum, is a much more simple compound than cane sugar. The glucose has only six atoms of carbon while cane sugar has eighteen; it has twelve OTHER USEFUL PLANTS 83 atoms of hydrogen only, whereas cane sugar has thirty-two; and six atoms of oxygen, in contrast with the sixteen atoms of the cane sugar molecule. We have elsewhere seen that starch is a com- pound of the same elements; differing, indeed, from glucose only in that it has ten hydrogen atoms instead of twelve, and five oxygen atoms instead of six. Stated in chemical terms, a molecule of starch that has had a molecule of water incor- porated with its substance in a chemical union, becomes a molecule of glucose; and, of course, the converse holds — a dehydrated molecule of glucose becomes a molecule of starch. But to build up a molecule of cane sugar from either starch or glucose requires the introduction and incorporation of many individual atoms, although no new kinds of atoms are required. It is simply that the molecule of cane sugar is a very much more intricate structure, made of the same material. The glucose molecule is, if you will, a simple dwelling; the cane sugar molecule an elaborate mansion. But the materials with which they are com- pounded are precisely the same. There is a good deal of uncertainty on the part of the chemists as to the exact way in which A HOP FIELD VISTA This view between the rows of hop plants was taken just before the vines were let down for picking. The vines are heavily laden with flowers, and it is necessary to pick these by hand, and just at the right time. Therefore the harvest season is always a busy time in a hop region. There is no mechanical device that gives any assistance to the hand picker in gathering this crop. OTHER USEFUL PLANTS 85 the various molecules of the different sugars and allied carbohydrate substances are built up. Some chemists regard a molecule of a sub- stance called methyl aldehyde, which consists of a single atom each of carbon and oxygen com- bined with two atoms of hydrogen as the basal form of carbon compound which the chlorophyll in the plant leaf makes by bringing together an atom of carbon from the atmosphere and a mole- cule of water. From this relatively simple carbon compound more elaborate compounds are built, through the introduction of varying numbers of additional atoms of carbon or hydrogen or oxygen, as the case may be, and all of the intricate juices and flavors and sweet and bitter principles of the various plants are thus compounded in the mar- velous laboratory of the plant cell. THE PRODUCT OF THE HOP Among the multitudes of compounds of the almost endless series in which carbon, hydrogen, and oxygen are joined through the agency of the plant cell, there is one that is of peculiar interest from the standpoint of the agriculturist, because it gives value to a plant that otherwise would be at best a troublesome weed, to be ignored and despised. 86 LUTHER BURBANK The carbon compound in question is the bitter principles known as lupulin and humulin, which are the really important constituents of the flower of the hop. This so-called alkaloid, with its exceedingly bitter taste, would never be suspected by anyone but a chemist of having the remotest relationship with sugar; yet, in point of fact, it is made of precisely the same elements that make the sweet content of the sugar cane's delectable juices. But the three essential elements are differ- ently assorted, as anyone might readily surmise who contrasts the bitter taste of the hop with the sweet taste of sugar. In fact, there are thirty-two atoms, of car- bon, and fifty atoms of hydrogen, with only seven atoms of oxygen making up the composi- tion of the alkaloid that gives the hop value. No one knows precisely what is the share of each element in giving any particular quality to a plant product. The chemist at present can only tear down the molecular structure and tell us of what it is composed. In the presence of the elaborate carbon com- > pounds that are represented by such substances as sugar and lupulin, he is like a barbarian stand- ing before a beautiful temple. OTHER USEFUL PLANTS 87 The barbarian could tear down the temple, but he could not rebuild it. Similarly the chemist can tear the carbon- hydrate molecule to pieces, but he cannot put it together again. He knows how to pull to pieces the molecule of sugar, for example, mak- ing it into a simpler form of sugar, but he cannot build up even the simplest form of sugar from elementary atoms, were these ever so freely supplied him. Carbonic acid is everywhere in the air, and water may be had for the asking. The chemist knows just how many molecules of water he should take to combine with just so many atoms of the carbon to make a molecule of sugar or a molecule of lupulin. But he does not know how to go about the task. His only resort is to appeal to the agricul- turist in the field, who deals with living labora- tories in which the method of compounding these intricate substances is understood. If the chemist would have sugar, he must seek it in the product of the cane or sorghum, or beet. If he would have lupulin, he must go to the hop vine, for this plant alone has learned the secret of its production. So it chances that the ancient calling of the agriculturist is as essential to-day as it has al- 88 LUTHER BURBANK ways been; and that it is necessary to cultivate different varieties of plants in order to gain the diverse products that man needs or desires as food or as aids in the industries. The particular product that a hop vine grows, and in the production of which it has an absolute monopoly, is used, as everyone is aware, mostly in the process of the manufacture of beer. No product has been found that makes a satis- factory substitute for the bitter principle sup- plied by the lupulin of the hop. The particular place in which the hop vine stores this bitter alkaloid, once it has manufac- tured it, is the curious conelike leafy seed case or envelope of the pistillate flower. Without doubt the plant develops this bitter principle and stores it there to give the seeds protection from the depredations of animals. But whatever its purpose, the bitter alkaloid provided by the hop was discovered at an early date to have value for the purposes of the brewer, and the hop vine continues to be grown in large quantities solely for the production of this alkaloid. The hop vine belongs to that somewhat numerous tribe of plants that grow the pistillate and staminate flowers on different vines. It is only the pistillate flower that is of value to the hop grower. But a few staminate flowers are OTHER USEFUL PLANTS 89 grown here and there in the field to fertilize the others, the cultivators feeling that the seed which would not otherwise be produced has at least the value of adding weight to the flower heads, and probably it adds lupulin also. The hop has been grown from prehistoric times, and the exact country of its origin is not known, although it is found growing wild in Colorado and New Mexico in the mountains. It goes without saying that different strains of hop vines differ in productivity, and in the amount of lupulin that their flowers secrete, and in the quality of the product. Certain Bavarian hops have lupulin of peculiarly fine flavor, but these are all less productive than the hops grown in America. THE SUGAR BEET The possibilities of stimulating a plant to out- do itself in the production of its characteristic carbon compounds are well illustrated by the story of the sugar beet. It was not much over a half century ago that the merits of this vegetable as a producer of sugar began to be seriously considered. The fact that sugar cane grows only in warm climates, and that here is a hardy plant that may be grown anywhere within the temperate zone, stimulated the older Vilmorin brothers of Paris, SUGAR BEETS AT THE FACTORY Within very recent years the beet has rivaled the sugar cane as the chief source of the world's sugar supply. This would have seemed quite incredible to the chemists of a century ago, who declared it impossible to produce sugar from the beets in paying quantities. But the plant breeders of Europe solved the problem of increasing the sugar content of the beet, until now it is one of the most profitable of crops. OTHER USEFUL PLANTS 91 France, who had learned that the beet produces a sugar chemically identical with that of the. sugar cane, to make inquiry as to whether it might not be possible to grow the beet on a com- mercial scale, and extract its sugar in competi- tion with the product of the cane. For a long time the attempt was not attended with great success. But it was finally demon- strated that the sugar beet, even in its then un- developed form, could be made available as a supplier of sugar on a commercial scale, and then the attempt began to be made to develop vari- eties of beet having a larger sugar content. It is said that the beets at first used contained only about six per cent of sugar. But by most careful scientific selection through a series of generations it has proved possible to increase the sugar content of the beet, just as the length of fiber of the cotton boll was increased, merely by paying heed generation after genera- tion to the individual plants that showed the best qualities, and saving the seed of these plants only for the raising of future crops. Year by year the sugar content of the best varieties of beets was increased until from 6 per cent it had advanced to 20 per cent, and in the case of some individual beets even to 35 per cent; and in a few cases as high as 36 per cent 92 LUTHER BURBANK has been secured from whole fields of beets in Colorado. This should be a wonderful stimulant to plant developers everywhere. There is perhaps no other case so widely known or involving such large financial interests in which a corresponding improvement has been made in a commercial plant within recent years. My own share in this work has been, until quite recently, that of an adviser rather than that of a direct experimenter. Some twenty- five years ago I was asked by the sugar-beet manufacturers of both Europe and America to take up the improvement of the beet. But while I gladly advised in the matter, and pointed out the lines of development through which further improvement might be expected, was unable to give personal attention to experiments with the beet, owing to the pressure of almost numberless other lines of investigation. More recently, however, I have experimented with varieties of the beet that were already very greatly improved, working with seeds supplied by prominent beet raisers who had developed their product by combining the qualities of ten or more varieties of Russian, German, French, and English sugar beets. The cross-breeding experiments through which I was endeavoring to increase still further the OTHER USEFUL PLANTS 93 capacity of the beet for sugar were, for reasons already several times repeated, neglected. But, so far as they progressed, they fell in line with almost numberless other series of ex- periments in plant development, and gave promise of the production of a beet that would have a higher sugar content than any beet hith- erto under cultivation. Just what may be the limit to the percentage of sugar that the beet can be expected to de- velop would be matter of mere conjecture, but that it will represent a considerable advance upon the percentage already attained is scarcely open to doubt. And even as the case stands, the sugar beet has attained a position in which it is, as we have already seen, a dangerous rival for the sugar cane. The producers of sugar beets have been at work while the producers of sugar cane were sleeping; and the results of their efforts consti- tute a triumphant demonstration of the value of scientific plant ex- perimentation as an aid to the practical agriculturist. RECLAIMING THE DESERTS WITH CACTUS THE METHODS USED TO PRODUCE A SPINELESS CACTUS PLAINSMEN will tell you that in the old days they have known the antelope and the buffalo to come for many miles to feast on cactus plants whose spines had been burnt off by a chance fire. The spines of the cactus burn like tiny tapers, leaving the slabs nearly unprotected, and the succulent forage thus made accessible consti- tuted a meal that was precisely to the liking of the antelope and the buffalo. Horses and cattle were found to relish the plant equally under the same circumstances. In the midst of the desert sands, with little else eatable in sight that was more inviting than the sagebrush with its dry, bitter, and dusty foliage, the succulent cactus slabs, held out in- vitingly, offered juicy herbage that the animals browsed on with avidity. 95 96 LUTHER BURBANK Even when the cactus still retained its spines, the antelope would sometimes try to find a way of getting at its juicy substance. I have heard plainsmen tell of seeing the antelope holding in its mouth a slab that had been dislodged, and twisting its neck this way and that in an effort to find an unprotected spot at which it could nibble; and horses and mules sometimes persistently kick the plants in their efforts to obtain the nutritious substance of the leaves and stems. Obviously the cactus had need of its spines if it was to escape the unwelcome attentions of the browsing animals that found such difficulty in securing sustenance among the scanty herbage of the plains and deserts. But by the same token it appears that if a way could be found to take from the cactus its bris- tling array of spines, the plant might be made to supply forage in regions where other succulents cannot secure a foothold. So the problem of pro- ducing a spineless cactus was one that had but to be suggested to anyone who knew the life of the arid regions to make instant appeal. MATERIALS AND RESULTS It was obvious, however, to anyone having any clear knowledge of plant development, that the THE CACTUS 97 task of removing the spines from the cactus would be a very arduous one. It is true that there are small species of cactus that are spineless, or nearly so, that have been familiar for generations. One of the first pets of my childhood days was a thornless cactus, a beautiful little plant of the genus Epiphyllum. There are also members of the Cereus family that are thornless, showing not a trace of spine on any part of the plant or fruit. But the cactus plants that are thus unprovided with spines were without any exception small and inconspicuous species, and also with a bitter prin- ciple so disagreeable that cattle generally refused to eat them. So the plants offered no possibili- ties of direct development through selection that could promise the production of varieties that would have value as forage plants. Meantime the large varieties, in particular the members of the genus Opuntia, which have pecu- liarly attractive qualities of size and succulence are thickly studded with spines for the very reason, doubtless, that were they not thus pro- tected they could never have maintained ex- istence in regions inhabited by the jack rabbit, antelope, and buffalo. If the problem of securing a spineless cactus of value as a forage plant — to reclaim the deserts -Vol. 6 Bur. THE CANDLE CACTUS No explanation is required as to how this cactus received its popular name. It is a species often grown for ornament in regions suited to it. This is a very old specimen about fifteen feet in height. Dwarf Opuntias and various other cacti at its base. THE CACTUS 99 and supply succulent food for herbivorous ani- mals where now little but sagebrush grows — was to be solved, it would be necessary, I thought, to hybridize the already well known, partially spineless species of cactus with the large-grow- ing, spiny ones. There seemed reason to hope that a reassortment of heriditary characters might be brought about, such as we have seen, for example, in the case of thornless black- berry and stoneless plum among other plant developments. Thus the qualities of size and succulence of the Opuntia might perhaps be combined with the smooth skin of the smaller, partially spineless species. The hope that it might be possible to effect such a transformation through hybridization was abundantly justified. In due time such a new race was developed, a gigantic cactus, overtop- ping all its known ancestors in size, and sur- passing them all in succulence of flesh, producing fruit of unpredicted excellence in almost unbe- lievable quantity, and having a surface as smooth as the palm of your hand. Such a plant was produced as the result of hybridizing experi- ments, followed up and supplemented by the usual methods of rigid selection. But the result was not achieved with the small cacti referred 100 LUTHEK BURBANK to. Meantime I was carrying on extensive experiments with all the half-spineless ones which had been well known for centuries. A SOUL-TESTING EXPERIENCE But the work through which this result was achieved constituted in some respects the most arduous and soul-testing experience that I have ever undergone. In carrying out the experiments, from the initial pollenizing through stages that involved the handling of seed and the constant handling of seedlings, I was obliged to associate most intimately with the cactus plants, and it was ab- solutely impossible to avoid their spicules. Par- ticularly after the work had advanced to a stage where the larger spines had been removed and the remaining spicules were in little bundles on the older joints, did it become impossible to handle them without filling one's fingers with the irritating prickles. For five years or more the cactus-blooming season was a period of torment to me both day and night. Time and again I have declared from the bottom of my heart that I wished I had never touched the cactus to attempt to remove its spines. Looking back on the experience now, I feel that I would not have courage to renew THE CACTUS 101 the experiments were it necessary to go through the same ordeal again. Not only would the little spicules find lodg- ment everywhere in my skin, but my clothing became filled with them, and the little barbs would gradually work their way through the cloth and into my flesh, causing intense irri- tation. At first much time was devoted in the endeavor to remove the very inconspicuous but exceed- ingly irritating and pain-producing little spicules with the aid of a magnifying glass and forceps. But it was ultimately learned that the only satis- factory expedient was to shave off the spicules with a sharp razor, or to sandpaper them off, which can readily be done where a great quantity is to be dealt with. When thus reduced in size they would not farther enter the flesh, and gradu- ally the pain would subside. But the recollection of the torture in con- nection with the development of the spineless cactus will always remain the most painful one associated with any of my plant de- velopments. No other complication comparable to this has been encountered in connection with the con- siderably over twenty-five thousand species of plants with which I have experimented. 102 LUTHER BURBANK But possibly it will appear in the end that no other series of experiments that I have under- taken can be compared in importance to the pro- duction of the race of spineless giants which tower to almost treelike proportions, and grow with such rapidity as to produce on good agri- cultural land from one hundred and fifty to three hundred tons of new forage to the acre by the third season after planting, besides nearly one- third as much fruit, yet which are as tender and succulent as grass, affording forage of fine quality in unprecedented quantity, and which can send their roots far into the earth and gain a supply of water for their sustenance from sub- terranean sources in regions where the surface of the country is that of the desert; and economiz- ing this for long seasons of drought which may follow. HEREDITARY TRAITS These new races of spineless cactus are of many varieties, in token of their varied ancestry. In producing them I followed my usual custom of securing material from every available source. The main supply came, naturally, from the arid regions of the Southwest, the original home of the cactus. But I received also plants from Minnesota, Montana, Dakota, New England, THE CACTUS 103 Missouri, and Colorado, South America, north and south Africa, and regions around the Medi- terranean. It could not be known at the outset just what crosses would be most effective, and so experimented on every species on which I could lay hands. I pollenized the giant Tunas with pollen of the little trailing cactus, and with such inconspicuous cousins of the giant as the little hardy Opuntia vulgaris. There were several small more or less spine- less species available, and others that produced a comparatively small crop of spines, and of course it was recognized from the outset that these must be our main reliance. Just as the little French partially stoneless plum had been the foundation for building the stoneless plums and prunes of to-day, it was thought that the little cactus that was smooth-skinned might fur- nish the element of spinelessness in all the future races of spineless cactus, however varied the other elements of their heritage. The most curious feature about the crossing of the giant Opuntias with the small species, in particular with the little cactus of the eastern United States known as Opuntia vulgaris, was that the hybrid was intermediate between the parents as to every characteristic but one. In size, stem, and manner of growth and form of THE GRAVITY CACTUS This new member of the spineless colony lias been named the Gravity from the unusual size and weight of the slabs. THE CACTUS 105 pads, it made a complete blend of the traits of the two totally dissimilar parents. But its blossom was a relatively enormous flower, very much larger than that of either parent. As to the blend of traits of this hybrid of giant and dwarf forms of cactus, the phenomena observed were obviously comparable to those that we have seen in sundry other connections. The Primus Berry, the Sunberry, and the Plum- cot will be recalled as illustrating the produc- tion of new forms, unlike either parent yet breeding true to the new type permanently even from the first generation. The hybrid between the giant and dwarf Opuntias furnishes another illustration of the same thing. This intermediate type, strikingly dissimilar to either parent yet obviously blend- ing the characteristics of both, bred true to form, showing nothing of that tendency to racial variation in the second generation that marks hybrids in general, and that, as will appear in a moment, marks the hybrids of the other cactuses very conspicuously. But there is an added element of great interest in the fact that the blossoms of the new hybrid so markedly differ from the flowers of either parent and so conspicuously excel either of them in size and beauty. 106 LUTHER BURBANK It would seem that the floral envelope occupies a position in the hereditary scale somewhat dif- ferent from that of the main stem of the plant. And this is perhaps not strange when we reflect that the flower is a relatively recent development in the history of plant life. We have already noted that flowering plants are of comparatively recent origin, geologically speaking. We have seen evidences here and there of the relative adaptability of the floral envelope as compared with the stem and leaf structure of the plant. So this new illustration of that phe- nomenon need not surprise us, however much it may interest us. It would appear, if we may interpret the phe- nomena just presented, that the giant and dwarf Opuntias have diverged so widely that they are practically at the limits of affinity that permit crossbreeding. The stems and main structures of the plant, therefore, refuse to conform to the principles of Mendelian segregation, and hit upon a compromise in which the traits of each plant find representation. But the flower, somewhat less fixed as to its characteristics, and indeed somewhat less widely divergent in the two species, accepts a compro- mise of a different order, and, under stimulus THE CACTUS 107 of that strange influence which we do not well understand but which we see constantly illustrated, it takes on a new vigor of growth. It surpasses the flowers of either one of its immediate ancestors somewhat as the hybrid Royal Walnut tree surpasses its parents in growth. This phenomenon of great vigor or tendency to excessive growth developed through hybrid- ization, is, as we have seen, a very common one; its peculiarity in the present instance is merely that here it applies to the flower of the plant alone, whereas elsewhere we have usually seen it apply to the entire structure of the plant, includ- ing at least in some cases (for example the Primus Berry, the Phenomenal Berry, and the Royal Walnut) the fruit as well. Let me add that when the Opuntias not quite so diverse in form as the giants and dwarfs were hybridized, the progeny showed the tendency to increased vigor of general growth, not merely to increase of the flower, although productivity was also emphasized. Indeed, it is to the fact of such stimulus of growth by hybridization that my success in developing the gigantic races of spineless cactus is due. 108 LUTHER BURBANK HYBRIDIZING MATERIALS AND METHODS The hand-pollenizing of the cactus, which was the foundation of these experiments in the pro- ducing of the new spineless races, presents no technical difficulties, yet requires to be carried out in a particular way. The cactus flowers open only in the very hottest part of the day, and within fifteen min- utes after the pollen bearers are exposed there is probability that the wind or bees will have accomplished self-fertilization of many of the flowers. It is necessary, therefore, for the experimenter to be on the spot, to anticipate the opening of the flower. Our method was to collect pollen in watch crystals, and, if necessary, keep it until the flowers we wished to pollenize were ma- tured. As the different varieties of cactus bloom at different seasons, it was sometimes necessary to keep pollen for a considerable period. When the plant to be pollenized is ready to bloom, nothing more is necessary than to remove its stamens just before they are matured, and to dust pollen from watch crystal with a camel's- hair brush over the receptive stigma, being care- ful not to allow the brush to become smeared THE CACTUS 109 with pollen from the stamens, lest the next pol- lenizing be vitiated. Each blossom thus pollenized is of course tagged to make permanent record of the cross, in accordance with the method detailed in an earlier chapter. It was customary, wherever possible, to make the cross reciprocal, although with the Opuntias as with other plants it appears to make little if any difference as to which is the staminate and which the pistillate parent. Here as elsewhere in the plant world the factors of heredity appear as a rule to be distributed impartially between pollen grains and ovules. The cactus plants that served as material for my comprehensive experiments aiming at the development of a spineless race of economic value were very numerous as to species and very widely diversified as to form and habit. More than one thousand species of cactus are listed by the botanist, and there is the greatest amount of variability, so that no two botanists are agreed as to the precise classification of all the forms. Of course I have not had every species of cactus at my disposal, but the number with which I have worked is very large indeed. For years collectors in all parts of the world have gathered specimens for me, and, as knowl- THE PROLIFIC CACTUS It requires but a glance at the picture to show that this cactus deserves its name. These young plants, only a few months old, are already crowding one another and, as it were, clamoring for space. Soon they will constitute an impenetrable jungle. THE CACTUS 111 edge of my work went abroad, even collectors who knew me only by reputation have sent speci- mens of one kind or another, until my experi- ment garden may be considered the great gathering place of the varied clans of the cactus family. In addition to the specimens received from private collectors, I received also a collection that had been gathered at Washington for botanical classification. Most of these were curious thorny specimens, and I think none of them was used in my successful experiments, although all of them were carefully tested. Some of the later acquisitions were sent by my friend, David G. Fairchild — slabs of three varieties from Sicily. I received also specimens from collectors and botanists from Mexico, South America, and Hawaii, as well as almost numberless varieties from all regions of the United States where any form of cactus grows. The so-called Smith Cactus, a variety introduced into California by Professor Emery E. Smith about forty years ago, proved of first value as a hybridizing agent. MANY SPECIES BUT MORE NAMES But it is almost impossible to gain a really accurate conception of the materials employed, 112 LUTHER BURBANK because of the great confusion of the classifiers, which has led to the ascribing of different names in many cases to the same species. For example, the variety which I received under the name "anacaniha3* (meaning "with- out spines") from Fairchild is identical with specimens received from the Department of Agriculture bearing only a number, and with others received from Italy on one hand, and from my collector in South America on the other, one of the numerous specimens coming under the name "gymnocarpa"; all of these were more or less spiny. It was often only by careful inspection and observation under hybridizing experiments that we could identify the various specimens as being of the same species, or same variety. Again the so-called morada, another species that proved of value, was first received under the name amarillo, meaning yellow, from near Vera Cruz, Mexico, it having been sent me by the late Walter Bryant, formerly of Santa Rosa. This I found to be practically identical with another specimen that had come from southern Europe, under the name of Malta. Mr. Frank L. Myer, my then collector in Mexico, later employed by the United States Department of Agriculture at a better salary THE CACTUS 113 than I was able to furnish, sent me a variety almost or quite identical with these which he found in a private garden in Trapuato. Another useful variety that came from various regions under different aliases was the form that has been grown in Florida and in California for the last thirty or forty years and which goes by the common name of White Fruit. There are marked variations in the color and quality of the fruit of this cactus, the pulp some- times being white and again variegated with yellow. Specimens from different parts of the world might at first sight be thought to represent different species or at least different varieties; but I have found different kinds of fruit growing on contiguous branches of the same plant. The large species of cactus , that grows commonly in the Mediterranean region, known there as Indian Fig or Barbary Fig, is closely similar if not identical with the species generally called Tuna in Mexico, although the fruit of the Mexican varieties is usually somewhat smaller than that of the Old World form. The name tuna is applied indiscriminately in Mexico to cultivated and wild species of the tribe, but the varieties are sometimes recognized by different 114 LUTHER BURBANK names, as Tuna Amarillo, Tuna Colorado, Tuna Blanca, etc. Another quite common Mexican form known as Tapuna appears to be entitled to recognition as a distinct species of Opuntia. It produces flat leaves that are generally circular or heart-shaped. The plant does not grow as rapidly as others of the large-fruit Opuntias, and the fruit ripens late in the season. The leaves have a somewhat white appearance, as if dusted with flour, which distinguishes them very readily from the others. The fruit is rarely edible except for stock. The Tapuna is also of rather exceptional com- pactness of growth and has high nutritional value as a forage plant. Moreover it is a much hardier species than many others, resisting both cold and wet better than most of the best Opuntias. So this species has characteristics of obvious value from the standpoint of the plant developer. THE QUESTION OF SPINELESSNESS But what about the matter of spines? This, of course, from the standpoint of the present investigation, is the vital question. The question might be answered categorically, with the statement that not a single one of the THE CACTUS 115 Opuntias received from any source was alto- gether spineless. Spineless forms of some of the other genera are familiar, but it was early dis-^ covered that the Opuntias must be looked to for the development of a race of cactus that would have economic value. And, as I said, no form of Opuntia was received, among all the hundreds of specimens from various parts of the world, that was altogether spineless and spiculeless. The form already referred to as the ana- caniha, of which specimens were received from various widely separated countries, came as near to spinelessness as any other form of true Opuntia. There is a very small and very tender species that is allied to the Opuntias, and very closely resembling them, but is classified as a Nopalia, which was received from various parts of California and Mexico, as well as from the Hawaiian Islands, the Philippines, and from Europe, under various names, which is alto- gether spineless. But this species is very sensitive to frost or to excessive heat, and in general succumbs to any untoward conditions so readily as to be value- less for this purpose, besides not being relished by any stock. YOUNG ROYAL CACTUS PLANTS Royal is a word that has attractive meanings when applied to plants, what- ever one may think of it nowadays in its application to the human being. This name would not have been given to this particular variety of spineless cactus had it not shown altogether exceptional qualities. To casual inspec- tion the most striking thing about it is its propensity to strike out in all directions, as if claiming all the land and air in the neighborhood as Us birth- right, but it is a wonderful forage producer. THE CACTUS 117 We have already referred to the fact that there are absolutely spineless forms of the genera Epiphyllum and Cereus. These, indeed, have been well known to me for fifty-five years, and are familiar to all students of plant life. But, as just noted, investigations showed that the genus Opuntia must be depended on for material with which to build an economic race of spineless cactus. This experiment, it will be understood, was intensely practical in its aim from the outset. It was not at all my thought merely to pro- duce an interesting race of spineless cactus of diversified forms. The spineless cactus of my ideal was one that would have practical value as a forage plant; one, therefore, that would grow luxuriantly in arid places, would be reasonably hardy and resistant to extremes of temperature, and would produce an abundance of succulent forage as well as a supply of palatable fruit. I repeat that I have still to see any form of Opuntia that is of good size and suitable for forage and yet that is altogether free from spines and spicules, except the ones that have been developed on my experiment grounds, and their progeny; and no such variety has yet been reported, although the authorities of the Agri- 118 LUTHER BURBANK cultural Department of Washington scoured the earth to find such a variety. These, indeed, are Opuntias fulfilling every specification of spineless forage plants of reason- able hardiness, great adaptability as to soil and easy culture, and enormous productivity; and they are wonderful fruit producers as well. But they are the result of a most arduous series of , experiments in plant development, and they con- ' stitute new races, entitled to the rank of new species if ordinary botanical standards are to be accepted, that have been developed here, and that, so far as there is any evidence, had never previously existed anywhere in the world. Their descendants have gone forth to begin the reclamation of the arid places of many lands, and also to be grown with profit even in the most expensive agricultural lands, especially for feeding with other forage crops. But in no land will they come upon a cactus from any other region that closely resembles them in their com- bination of entire spinelessness and inviting forage qualities. PARTIALLY SPINELESS MATERIAL Yet it must be understood that the various specimens of cactus that have been sent me from all over the world, many of which were utilized THE CACTUS 119 in crossing and hybridizing and selective experi- ments, were often forwarded under the supposi- tion that they were specimens of spineless races. And many of them were relatively spineless. Some of them showed individual slabs that were almost free from spines. But without exception these plants, notwith- standing their relative smoothness, would be found to have inconspicuous spicules or bristles, which constituted an armament almost as offensive as the larger spines ; or else would soon demonstrate that their spinelessness was an indi- vidual peculiarity rather than a trait of the race to which they belonged, by developing spines on new slabs. Yet the fact that partially thornless Opuntias exist in many regions demonstrates a tendency on the part of this plant to give up its spines partially under some circumstances. It shows that in the heredity of the plant there are strains of spinelessness that might presum- ably be utilized by the plant developer in the production of a spineless race. In particular it was learned that there is in the Hawaiian Islands cactus that develop speci- mens that are partially thornless when grown on mountainsides in positions absolutely inacces- sible to browsing animals. Also in California, 120 LUTHER BURBANK Mexico, Colorado, New Mexico, and Texas, as I learned from various reports, small patches of half thornless cactus are sometimes found, always in inaccessible crevices among the rocks. These all appear to be species of Nopalia and not Opuntia. In some of the South Sea Islands where vege- tation is abundant, and where browsing animals are few, the Opuntias have either reverted to a partially spineless condition, or have re- tained spines that have become merely hairlike appendages, but these are extremely tender and of no use whatever, even in subtropical climates. This tendency to produce partially spineless races when the plant is grown under conditions that make it inaccessible to browsing animals, seems clearly to demonstrate that there are obscure factors of thornlessness in its prehistoric heredity. Our general studies in the effects of hybridizing give adequate clues as to the way in which these submerged factors may be brought to the surface. The open secret, of course, is to blend the dif- ferent strains of heredity by hybridizing the vari- ous Opuntias, and to select for propagation the seedlings that reveal the spineless condition in combination with other desired qualities. THE CACTUS 121 A SPINELESS RACE ACHIEVED From the outset I had been making hybridiz- ing experiments in which I utilized in particular the hardiest races of Opuntias that could be found, choosing, of course, at the same time, those that showed a tendency to produce rela- tively sparse crops of spines. In this way I had developed races of cactus that though small in size were hardy, and that ultimately, after nine years' work, produced specimens that were absolutely free from spines. After the spines were gone, however, there re- mained spicules, which grow in little clusters of several hundred here and there over the surface of the joint, and which are an even greater annoy- ance than the larger spines to the plant experi- menter, although they are sometimes ignored by browsing beasts. At the present day absolutely smooth ones have been produced on my grounds, bearing handsome fruit of excellent quality. The hardy and partially spineless cactuses first produced were hybridized, when my more exten- sive experiments were under way, with the best examples of the large Opuntias received from all parts of the world. In making these crosses I bore in mind always the condition of relative spinelessness, but also THE HEMET CACTUS Contrast these nearly round, flat, robust slabs with the relatively slender ones shown in some of the preceding pictures. Note that the new slabs are dimpled where the embryo leaves have been. They will be as smooth as the older slabs in due course. THE CACTUS 123 the characteristics of the plant as regards size and fruit production and quality. The precise parentage of the hybrids of the first generation was recorded, as already stated. But when the seedlings came to be handled by literal millions, and when the specimens that were utilized numbered scores of alleged species, be- tween which it was often difficult to differentiate, it finally became impossible to attempt to follow the exact pedigrees of the selected plants, if my experiments were to be carried out on the ex- pansive scale that was contemplated. The seeds from different crosses were planted separately, and the character of the seedlings would reveal at an early period the quality of the plant as regards the tendency to produce spines, but not at this early stage the quality or quantity of fruit. When the cactus seedlings first appear above ground, their cotyledons are spineless. This sug- gests a period when all cactus plants were with- out spines, for it is a familiar doctrine that the developing embryo reproduces in epitome the stages of its racial history; and the plant at the cotyledon stage may be regarded as really still an embryo, inasmuch as it is drawing its nourish- ment from the nutritive matter stored in the seed. 124 LUTHER BURBANK The first leaf that puts out just above the cotyledons may be spiny or hairy, in recognition of the racial period when spines were worn. But the quality of these little spicules will enable the experienced experimenter to determine whether they represent future spines or only a racial reminiscence. So it is possible to make first selection among the seedlings at a very early period, and to weed out from among the hundreds of thousands all but a few. Unfortunately the cactus requires from three to five years from the seed to come to fruiting time. So the experimenter who is attempting to develop an improved spineless race must wait patiently throughout this long period before he can effect a second hybridization and thus carry his plant one stage farther along the road to the coveted goal. But by carefully selecting the seedlings that show the most likelihood of a propensity to pro- duce smooth slabs, yet which at the same time are strong of growth and resistant to unfavorable conditions, it is possible to note marked progress even in a single generation. And when the selected plants have come to blossoming time and have been hybridized with the best among their fellows, the seedlings of this second generation THE CACTUS 125 will show numerous individuals that are mark- edly superior to their parents or their grand- parents in regard to all the desired qualities. In the second generation (we are not now speaking of the giants and dwarfs referred to earlier in the chapter) is manifested the usual tendency to recombination of the hereditary factors. In such companies of seedlings as I developed, where hundreds of thousands of plants are grouped together, one is sure to find at least a few specimens that combine the spineless quality of one remote ancestor with the tendency to large growth of another, the fruiting capacity of a third, and so on. By attentive scrutinizing of the seedlings, at an early stage of their development, it was found possible to select thus the few in- dividuals among the thousands that revealed the best combinations of qualities. These are transplanted by themselves, and given every favorable condition to stimulate their growth and development, and finally placed in long rows for field culture, where they are al- lowed to stand for three or four years, and in the end, if one out of three hundred or four hun- dred is found sufficiently valuable with which to continue the work, the experiment may be con- sidered successful thus far. 126 LUTHER BURBANK It is tedious to wait another term of years be- fore going to the next hybridizing experiment that will give a still better crop of seedlings from which to make new selections. But of course numberless experiments with other plants are being carried out in the interval, and so the time does not seem so long while it is passing as it seems in retrospect. Let it suffice that after fifteen years of effort, involving the collection of materials from all over the globe, the hybridizing in the aggregate of thousands of individuals, and successive selec- tions among literal millions of seedlings, I was at last rewarded by the production not merely of one but of numerous varieties of hybrid Opuntias that grow to enormous size, producing an unbelievable quantity of succulent forage ; the slabs of which are as free from spines or spicules as a watermelon; and that produce enormous quantities of delicious fruit. Some inkling, perhaps, of the difficulties of the experiments through which this result was achieved have been revealed in the preceding pages. Something of the economic importance of the achievement will be suggested in the pages that follow. Here let it suffice to repeat that the series of experiments in which the giant spineless fruit- THE CACTUS 127 ing Opuntias were developed was in some re- spects the most painful, arduous, and difficult of all my long series of plant developments ; and that there is reason to believe that its results will ultimately vie with the results of any other single experiment in economic importance. Here is a new species of spineless giant cactus which towers to almost treelike proportions, and grows with such rapidity as to produce, on good agricultural land, from one hundred and fifty to three hundred tons of forage to the acre by the third season after planting, besides nearly one- third as much fruit. THE COMMERCIAL POSSIBILITIES OF CACTUS AS CATTLE FOOD The right of introduction of certain of the first of my spineless cactus productions in the Southern Hemisphere was sold to Mr. John M. Hutland, of Australia. Mr. Rutland had come to Santa Rosa to ob- serve my experiments, and desired to take back with him the Spineless Cactus along with certain other of my new products, including the first of the Plumcots. He very gladly paid one thousand dollars for a single slab of the most important of the new Opuntias, and somewhat smaller sums for slabs THE MELROSE CACTUS One of our improved, rapid- growing forage Opuntias just starting on their second season's growth. The fruit is hardly edible. THE CACTUS 129 of several other varieties. He purchased the privilege also of introducing the new plants throughout the Southern Hemisphere. This was the first financial return for the work on the Opuntias. It practically paid for the building of my new home, but, of course, fell far short of the sum expended on the cactus experiments. A little later a company, formed to control the introduction of the plant in the Northern Hemi- sphere, paid me a large sum for my interest in the entire stock, including one or two hardy hybrids that had value for further experimental purposes. The original sale included individual slabs of the different varieties. The later de- liveries included more than fifty tons of slabs and plants, constituting the tangible results of the long series of experiments. My experiment farm, however, still has a large quantity of Opuntias in various stages of devel- opment, but particularly those that are being developed for their fruiting qualities. Not less than five hundred tons of forage — as nearly as can be estimated — are now standing on less than an acre at Santa Rosa. As forage plants, the spineless Opuntias already developed have attained a degree of per- fection that leaves little to be desired. 5 — Vol. 6 Bur. 130 LUTHER BURBANK PROPAGATION or THE SPINELESS OPUNTIAS It should be understood that the new varieties of Opuntias, while as a whole they may be re- garded as constituting a new species, are indi- vidually comparable to the different recognized varieties of any given orchard fruit, like the best apples, or pears, or plums. That is to say, they may be indefinitely propa- gated by division, and all the plants grown from the original individuals will retain the essential characteristics of the original. But, like apples, ipears, and plums, they cannot be depended on to transmit their best characteristics unvaryingly from the seed. With the new Opuntias, as with the orchard fruits and so many cultivated plants, the various hereditary factors are blended in more or less unstable combinations, and this instability will be revealed in the offspring grown from the seed. So the recognized method of propagating the Opuntias is to plant a slab, and to let this serve as the foundation from which roots and branches will grow. The slabs that develop on each plant may of course be similarly cut off and planted, so that a large territory may be rapidly covered with cactus plants, all precisely like the original. THE CACTUS 131 Mention was made in a previous chapter of certain cases in which an individual cactus slab that was practically without spines might de- velop other slabs that would be spiny. This could only occur, however, in case the slab in question was an individual variant which owed its lack of spines to some local condition of altered nutrition. A slab growing as a part of a plant that is spineless throughout will produce only spine- less plants, with the exception of very rare bud sports which appear on all plants from time to time. The case of the Opuntias in this regard is pre- cisely comparable to that of the orchard trees that are propagated by grafting. In each case the entire crop of plants, although multiplied until the offshoots of a single plant may cover hundreds or thousands of acres, really constitutes essentially one plant with divided personality, rather than successive generations of plants. SPINELESS CACTUS FROM THE SEED Yet the important question has arisen as to what will take place when the transplanted Opuntias, once they have come to populate the arid places, produce fruit, and scatter their seeds. The answer is that no bad results will ensue. 132 LUTHER OBURBANK The reason is that the best new hybrid Opun- tias have been found to be seedless ; or, where the seeds are not entirely eliminated, they are re- duced in size and have lost vitality. In my ex- ,( perience, then, when the fruit of the improved species have ripened and dropped to the ground, under the most favorable possible circumstances, no seedlings have been seen; whereas, when the fruit of the wild ones drops there are abundant seedlings. The case is comparable to that of the Shasta daisy, which never spreads from the seed, unlike its wild prototype. When the Shasta was first introduced, one of the Western States passed a law forbidding its growth in the State. At the present time the Shastas are grown by the mil- lions in that State, as well as in all other regions of the world, and no one has ever complained. With care in propagating, and reasonable pro- tection, the new spineless Opuntias constitute a race that gives every assurance of permanency. Yet it should not be forgotten that this race has been developed under conditions of artificial selection, and may need man's protection while it is establishing itself in any given region. The new spineless Opuntias represent a race that has been permitted, through the fostering influence of artificial selection, to develop, not- THE CACTUS 133 withstanding its loss of the protective spines. Now that it has been developed, and the spine- less condition combined with the traits of prolific growth and abundant bearing, the race which could never have made its way under natural con- ditions may be sent back to the desert to provide forage for animals in almost unbelievable quantity. But even now it will be necessary to protect the plants from the herds. It is only after the Opuntia has attained a fair growth that it could withstand the attacks of the herbiv- orous animals, which find its succulent slabs altogether to their liking. Some uninformed newspaper reporters have unfortunately given the impression to the public that the seed of the improved varieties could be sown on the desert land like wheat, and grown without fencing or other protection. Let us ask, what crop that man values in any country is not fenced? The more valuable the crop, the more carefully must it be protected. The very fact that all herbivorous animals relish these new creations proves their value and the necessity for protecting them. BOTH FOOD AND DRINK So thoroughly appealing, indeed, is the flesh of the cactus plant to the palate of the herbivo- SPINELESS CACTUS SHOWING SIX MONTHS' GROWTH This picture shows the rapidity of growth of some of the improved varie- ties of spineless cactus. The central slab originally planted has put forth several offshoots, and these, of course, have sent out numerous branches; so that now, only six months after the time of planting, the plant begins to take on the aspect of a cactus colony. Rapid growth is one of the important factors which must be constantly kept in mind in making selections, especially for forage varieties. THE CACTUS 135 rous animals that many of them will feed on it even when the slabs are protected by spines. There are regions in Mexico and Hawaii where the cattle feed habitually on wild species of Opun- tias, even though this involves the habitual in- gestion of millions of spines and spicules with which the slabs are protected; resulting quite often in sickness or death of the animals. The manager of a ranch in Hawaii, writing to the editor of the "Butchers' and Stockgrowers' Journal," of California, under date of April 17, 1905, declares that on his ranch there is a pad- dock of 1,200 acres covered very thickly with cactus or prickly pears, with only a slight growth of Bermuda grass. In this paddock, he tells us, are pastured all the year round 400 head of cattle and about 700 hogs. For both cattle and hogs the cactus furnishes the chief food. The hogs receive only a slight ration of corn, fed to keep them tame, and for the rest live exclusively on the young leaves and fruit of the cactus. Both cattle and hogs thrive wonderfully. But when the cattle are killed, it is found that the walls of their first stomach are filled with myriads of small spines. The manager adds that he has never known an animal to die from the effects of these spines. This is a half dwarf, partially 136 LUTHER BURBANK spineless variety, which is sometimes found in tropical islands. Yet it is obvious that the spines cannot add to the health of the creature, and it is hardly to be doubted that the animals will appre- ciate the giant spineless varieties when they have access to them. But the most remarkable part of the story re- mains to be told. This is the fact that the cattle have water to drink only during the rainy season, which usually includes the months of December and January. During these two months there is a certain amount of grass and they have water to drink. But during the other ten months of the year the cattle subsist exclusively on the fruit and young leaves of the cactus. They receive not a drop of water except as they find it in the succulent cactus slabs. "Yet," the narrator continues, "it is a remark- able fact that during the dry months of the year we get a higher percentage of fat cattle from that paddock than from any of the others." He adds that he considers the cattle fed in this way on cactus to make as well-flavored beef as any that he has tasted in San Francisco and New Zealand. Another record of the same sort is given by Mr. Robert Hind, a millionaire sugar planter THE CACTUS 137 arid ranchman of Honolulu, who declares that on his ranch in Hawaii he has horses that "do not know what water is and will not drink it if it is brought before them. They have never tasted water." "I have good, fat cattle," Mr. Hind continues, "that have never seen water and would not know how to act if water touched them. I have other cattle that I have imported from the United States which have not tasted a drop of water since being turned out on my cactus and blue grass pastures. They have lived for years without water, and are as fat as any grass-fed cattle in the United States. They make just as good beef as you can get in any restaurant." To anyone who knows the prime necessity of a water supply for cattle and horses under ordi- nary conditions of grazing, such statements seem almost incredible. But they are thoroughly au- thenticated and, indeed, they need excite no sur- prise in the mind of anyone who appreciates the succulent quality of the cactus slab. In fact, the entire cactus plant is a nutritious receptacle for holding water. It was doubtless because the leaves of the cactus transpired water, as do all leaves, that these ap- pendages were given up, so that the cactus of to-day is a leafless plant. A plant that grows in 138 LUTHER BURBANK the desert finds it necessary to conserve water. So through natural selection the cactus developed the custom of dropping its leaves when they were only tiny bracts, at the very earliest stage of its growth, developing chlorophyll bodies in its slabs to perform the functions usually performed in the leaf of the plant. These present a relatively small surface to the air in proportion to their bulk, and conserve in large measure the water that would be transpired from an ordinary leaf system. This, combined with the habit of the cactus of sending its long, slender roots deep into the soil, accounts for the power of the plant to grow in arid places. It is not that the cactus can perform its life functions without water any better than can an- other plant. It is only that the cactus has learned how to seek a water supply in the depths, and to conserve it after it has been found. What the cactus does then, essentially, is to bring water from the depths of the parched earth, and to store it in its flat slabs, along with nutritious matter, so that these constitute both food and drink for the animal that eats them. It is obvious that a plant that has such charac- teristics, now that it has been relieved of the spines that were hitherto its greatest drawback, THE CACTUS 139 and quadrupled in productiveness — with a good prospect of increasing it one thousand per cent — constitutes a forage plant that is in a class quite by itself. The importance of this forage plant is already widely appreciated, but it will be more and more fully understood as the years go by. ENORMOUS PRODUCTIVITY or THE NEW OPUNTIAS Not only is the quality of forage produced by the new species of Opuntias of a character to recommend it most highly, but the quantity of forage produced by a given acreage is altogether without precedent. Moreover, being available throughout the year in a succulent form, it is peculiarly valuable for feeding milch cows, producing a greatly increased flow of milk. The plants grow rapidly from cuttings, and only a few months are required to produce a growth that begins to present forage possibilities. Of course it will be better to allow the plants to grow for two or three years, and thus* attain large size, before slabs are cut away. But after that the new growth may be removed from time to time as required, and the plant will be a con- stant forage producer for a century at least. A FRUIT COLONY Here are forty-three fruits on a single slab of one of my spineless cactus — one highly developed for fruit- ing. The slabs do not often quite duplicate this record, to be sure, but sometimes even exceed it. Thirty tons to the acre is a good yield of fruit like this. THE CACTUS 141 The different varieties of new spineless Opuntias vary greatly as to size, but all are plants that on good land attain a growth of six or ten feet in height and across during a few seasons, and some of them grow much larger; a four- year-old plant often weighing half a ton or more. There is a good deal of difference also as to size and weight of the individual pads or slabs. Many of these weigh eight or nine pounds, al- though the average is from two to six pounds for the improved varieties. Some of them weigh as high as eighteen to twenty-two pounds, but these are exceptional. But the varieties having largest slabs do not necessarily produce the greatest amount of food. One of the new varieties of the gigantic Tuna type has produced a slab four and one-half feet in length. This, of course, is some- thing quite out of the ordinary; but slabs from twelve to eighteen inches in length are by no means unusual. The growth of the plants is so prolific that the total weight of the new slabs grown in a single season, under favorable conditions, has been esti- mated at almost one hundred tons to the acre. On the best agricultural grounds, as on my own grounds at Santa Rosa, the plants have produced quite five hundred tons per acre in their first four years of growth. This is from some of the most 142 LUTHER BURBANK highly improved varieties, on the best of land, but without irrigation or special fertilization. Of course this growth would not be duplicated on all soils or under all conditions, but even in inferior soils the growth of the Opuntias is phe- nomenal, and the amount of forage produced each season is greatly in excess in weight of that produced by any other forage plant, not except- ing alfalfa. When the extraordinary weight of fruit that is borne by some varieties is further taken into consideration, it becomes evident that the new spineless Opuntia is the most productive plant ever cultivated. It is within the possibilities that a field of Opuntias, under ideal conditions of cul- tivation, might yield in new slabs and in fruit an aggregate edible product approximating four or five hundred tons to the acre. This has already been attained in smaller areas. As to soil, the Opuntias grow everywhere. They may be planted on rich level land, or on the steepest and poorest rocky hillside, along old river beds, and among rock piles. But it must not be inferred from this that the plant is oblivious to good treatment. The growth and succulence of the slabs are greatly increased by good soil. Reasonable cultivation of the soil is also of benefit, and, under semiarid conditions, THE CACTUS 143 a very slight irrigation once during the dry season will be highly beneficial, but not absolutely neces- sary, as the plants will live where not a drop of rain falls for many years, if the soil is not too fiercely sun-baked. By such treatment the fruit is greatly in- creased in size and improved in quality, and the slabs for forage are doubled in weight. In a word, no plant responds more promptly to good treatment than does the Opuntia. Yet, on the other hand, the plant retains the primeval capacity of its ancestors to make its way under the most unfavorable conditions. MAKING A FORAGE AND FRUIT FIELD Unlike most other plants, the Opuntias root best during the heat of summer. This is also the best time to transplant them. In fact they should not be moved at other seasons. ,No one who is familiar with the Opuntias would undertake to root or transplant them during the cold, damp weather, such as would be best for other plants. But if transplanted during May, June, July, August, or September they will thrive under al- most any treatment. The joints, blossoms, buds, half-grown fruit, or any part of the plant will take root and grow under the most discouraging circumstances. I have seen them develop on the 144 LUTHER BURBANK floor back of a cookstove, in the pocket of a winter overcoat, lying on a writing desk, and in similar unlikely places. The Opuntias differ from nearly all the other plants in that cuttings must first be wilted before they will grow (unless in the dry, heated part of summer) ; after which nothing grows more readily. When you receive cuttings, place them in some warm, sunny place, and allow them to remain a week or more, after which they will readily form roots and start to grow almost anywhere. They may best be planted so that about one-third of the cutting is below the soil. The cutting may be planted in an upright position, or at any angle — such details make no difference to the Opuntias. On fairly good soil, to provide a forage field for stock feed, the giant Opuntias should be planted alternately in two rows together at in- tervals of three or four feet, according to variety, and then a space of ten or twelve feet left, and another pair of rows planted in the same way. This has been found to be the best way to plant the cactus, as by this arrangement space is left for general cultivation and for gathering the crop; otherwise the plants would too completely cover the ground. THE CACTUS 145 The young plants must have protection from marauding beasts. Squirrels and rabbits are particularly fond of the young slabs, and in a country infested by these creatures it may be necessary to fence in a field of young cactus un- til it attains a considerable growth. Needless to say, it must be protected from the encroach- ments of farm animals, as they would destroy the young plants utterly. When the Opuntias attain a reasonable size, it becomes, as already pointed out, a perennial source of forage. The plants live to an indefinite age, and year by year they put out new slabs, which may be cut at any season for feeding purposes. It is best to cut the forage, and not to give the animals access to the growing plants, as in the latter case they would waste the feed and seriously injure or destroy the plants. The cen- tral stems of the old plants, however, attain a woody character that generally protects them against extermination by stock. In practical feeding, it is desirable, where possible, to combine the Opuntia slabs with alfalfa, bran, and other carbonaceous and es- pecially dry foods, like straw, hay, and the like. The Opuntia slabs may be fed as an exclusive diet, and in this case farm animals will have no 146 LUTHER BURBANK craving for water. But in fact the cactus is not a complete feed, and it is always more economi- cal to feed some dry food with it, alfalfa hay being one of the best, to complete and round it out as a nitrogenous diet. Almost without exception, herbivorous ani- mals are fond of the cactus. Cattle prefer it to almost any other food, and it makes a superior quality of beef, and exceedingly rich milk, which is not surprising considering the succulence of the cactus and the fact that it contains a relatively large percentage of the salts of sodium, potassium, and magnesium. A very superior quality of pork is produced from pigs fed on the cactus fruit. The fruit is used also with success as a poultry food. The plant has been fed to horses, which, however, are said as a rule not to relish it until they become accustomed to it. But the merits of the cactus as a food for ani- mals have too long been recognized to require extended comment. The wild thorny cactus is frequently prepared for stock feeding by burn- ing off its spines, and in Australia the leaves and fruit of the dwarf and horribly thorny kind are boiled to make them available as food for hogs, especially in long seasons of drought. THE CACTUS 147 Such facts sufficiently attest the value of this plant, as well as its palatability. The spines which have hitherto constituted the one perennial drawback having now been re- moved, and the plant itself having been made to reveal new capacity for growth and for the production of flesh and fruit of peculiar succu- lence and food value, the cactus, as represented by the new races of spineless Opuntias, must take a leading place among forage plants in all arid and semiarid districts, where the climate is semitropical. THE CACTUS PRODUCES MANY MORE OR LESS USEFUTL SUBSTANCES The chemical content of the cactus slabs de- pends largely on the variety and also to a certain extent upon the age of the slabs. The young shoots in the early period of their growth have a very high water content, as is the case with all succulent herbage. The amount of crude fiber in the leaf at this stage may repre- sent less than one per cent of the total bulk. On the other hand, the old slabs and the main stalk of the plant take on a growing percentage of woody fiber, which renders them less and less palatable, but which adds to their value from another standpoint, as will appear presently. CACTUS BLOSSOMS A glance at this picture mil make it clear that the cactus has full claim to consideration as an ornamental plant, and is worthy of a place in any flower garden. It has such important economic uses as a forage plant and producer of fruit that its flowering qualities are usually overlooked. But they are not likely to be overlooked by anyone who has once seen a group of the new spineless Opuntias in blossom. THE CACTUS 149 The slabs during the period of their best de- velopment, when they would ordinarily be used for forage, contain, according to chemical analy- sis, from 2.71 per cent to 4.6 per cent of starch and its equivalent, with from .58 per cent to .72 per cent of protein, and .96 per cent to 1.68 per cent of mineral salts. There is also a very small amount of fat, which like the other nutri- tious elements is being increased in quantity in some of the newer varieties. The varying amount of these food constituents suggests that the quantity may be considerably increased by selection. Of course the same thing is true of the other constituents. No doubt the protein content, for example, may be increased by selective breeding, just as we have done in the case of corn. And in general the constituents of the Opuntia slabs that give them food value may doubtless be in- creased by careful combination and selection. Hitherto the development of the plant has been carried along the lines of spinelessness and great size and productivity; although, even as the case now stands, there has been a consider- able improvement in the percentage of food constituents. Even at the present time, however, the slabs of the Opuntias furnish fodder of highly nutri- OL50 LUTHER BURBANK tional character. That there is also a high water content is no disadvantage in a plant growing in arid regions. On the contrary, we have seen that this is to be regarded as one of the greatest merits of the plant, inasmuch as it enables animals to secure their water supply by eating the slabs, thus maintaining health and growth even when no drinking water is avail- able for months together. The qualities of the cactus fruit have been dealt with elsewhere. It will be recalled that there are numerous varieties of fruit, differing almost as widely as the varieties of apples. The essential character of all the fruits of the improved varieties, how- ever, is a peculiar juiciness of pulp, combined with individuality of flavor and in some cases a faint trace of acid. The fruit of the wild Opun- tias has sometimes been characterized as lack- ing flavor. But constant attention has been paid to the bettering of the fruit and the fruit of the new varieties is very popular with all those who are acquainted with it. On my grounds the choicest varieties of fruits of many kinds are grown, but the workmen usually prefer the fruit of the Opuntias to any other that is in season at the same time. THE CACTUS 151 The improved fruits are also rapidly gaining in popularity in the markets. When shipped to the east they bring about the same price as the best oranges, and the fact that they can be produced at a fraction of the cost of growing the orange should give them importance from the standpoint of the orchardist. Reference has been made also to the fact that the fruit has excellent qualities for making pre- serves and jams and jellies. The scarlet and crimson varieties have value in supplying color matter for other fruit preserves, ices, and con- fections. This newer vegetable pigment, with its beau- tiful shades of color, should largely supplant the objectionable aniline dyes that are now so gen- erally used to color ices and confections and nonalcoholic beverages. THE FOOD VALUE OF THE "LEAVES" In countries where the cactus grows abun- dantly, it has long been known that its young slabs make a palatable form of greens when cooked. In recent years some scientific experiment- ers have made the attempt to test the food value of the leaves of the partially improved cactus. 152 LUTHER BURBANK The cactus leaves when fried are a substitute for some of the poorer vegetables. Tender leaves should be selected, the skin peeled off, and the plants fried rapidly in butter. Appetizing preserves may be made from the fruit, some- what after the manner of apple butter. The fruit itself may be dried and thus preserved for winter use. With the production of 25 to 50 tons an acre, there is opportunity to preserve the fruit on a commercial scale, if a sufficient market for it can be developed. To me it seems that the cooked fruit lacks the fine flavor of the raw fruit. In general the fruit may perhaps be served to best advantage as a salad. But I have on several occasions had jars of delicious jams, made from cactus fruit, sent me from different localities. The fact that the fruit of the perfected Opun- tias contains a high sugar content, amounting sometimes to from 12 to 16 per cent, makes it obvious that this plant might be used for the pro- duction of methyl alcohol. The slabs may be used for the same purpose, and the enormous productivity of the plant would make amends for the comparatively low percentage of fer- mentable starch in the composition of the slabs. THE CACTUS 153 As A FAMINE PREVENTER It has been estimated that the improved Opun- tias produce foliage and fruit so abundantly that they could be grown advantageously on land that cost even one thousand dollars an acre. Analyses made by the Agricultural Depart- ment of the State University of California have shown that the new varieties greatly exceed the old ones in nutritive qualities. Yet even the un- developed Opuntias have long been recognized, particularly by the peoples of the Mediterranean as having high food value. The importance of the new plants as sup- pliers of food for human beings, in regions sub- ject to occasional or habitual shortage, has been recognized by several governments. The German Government before the World War was testing these new Opuntias at several places in its possessions in Africa. In parts of India where famines threaten and from time to time destroy millions of people, my new spineless cactus is being planted for the purpose of tiding the people over in the years of famine, even if not used as a part of the regular dietary. The plants have been introduced to Aus- tralia. They are also being tested in Brazil, 154 LUTHER BURBANK Argentina, Paraguay, Chile, Peru, and in other parts of South and Central America and Mexico. The new Opuntias differ from almost every other plant, and may be said in a way to re- semble canned food, in that their food content remains in perfect condition on the plants year after year until needed. Nothing more is re- quired than to plant the Opuntias, and fence them against the encroachment of animals. It is not necessary to cultivate them, although it is advantageous during the first two or three years, nor need any attention be paid them until their slabs are needed. They would thus grow enormously and when the occasion arose they would supply an almost indefinite quantity of food to meet the needs of a population that otherwise must die of starvation. The value of a plant that need not be culti- vated and needs no preparation yet which will perpetually hold in reserve a colossal quantity of food per acre, constantly adding to it (the an- nual increase being measured in scores of tons), offers a refuge to populations that are threat- ened with years of drought and failure of cereal crops that is not duplicated by any other food produced hitherto under cultivation. THE CACTUS 155 Even if the new spineless Opuntias had no other function than this, the time and labor de- voted to their production would obviously be repaid a millionfold. IMPORTANT BY-PRODUCTS There is one curious property of the slabs of the Opuntias that to some extent militates against their popularity as foodstuffs. This is the fact that the leaves contain a mucilaginous substance, the quantity of which, however, varies widely with the different varieties. The varieties that contain less of the muci- lage are used by the Mexicans for the making of confectionery. Some of the finest confections of Mexico are canned cactus leaves. The leaves also make excellent pickles, the only drawback to which is the presence of the mucilage in the case of some varieties. Those that lack the mucilage make pickles as fine in flavor as the best cucumber pickles. On the other hand, the mucilage, while unde- sirable from one standpoint, is not without its value. It may be extracted by cutting the leaves in thin slices, and placing them in water. One or two slabs will make a gallon of good, thick, perfectly transparent mucilage. When this substance dries slowly, it produces a gum CAOTUS CANDY Here is a tray of delicious candy made from the cactus. The Mexicans have long been accustomed to make various confections from the wild ones. With the new fruiting varieties, with their greatly enhanced crops now avail- able, it may be expected that cactus candy will gain in popularity. No con- fectionery can surpass well-made cactus candy. 7 THE CACTUS 157 that is generally white or of a pearly color, and not easily dissolved in water. The mucilage is often used locally to mix with whitewash, to which it gives something of the permanency of a paint. It is also used at times for stiffening sleazy cotton goods, and for water- proofing cloth. Beyond this the economic uses of mucilage have not been developed. But sooner or later some one will find use for this by-product of the, cactus, for the dressing on a large scale of fabrics, or any one of the hundred purposes to which mucilaginous substances are put. I have made many tentative experiments to test the qualities of the mucilage, but these have not been carried far enough to produce conclusive results. The Opuntias have possibilities of a quite dif- ferent character, connected not with their juices, or pulp, but with the woody fiber which makes a network in the older leaves and which comes to form the main substances of the central stalk. It has been found that this woody network, when the pulp is removed, makes a clean white fiber that is in the most beautiful condition for paper making. The older stems and roots fur- nish the fiber in considerable quantities, and even the roots are available for the purpose. The 158 LUTHER BURBANK amount of paper stock varies much in the dif- ferent species. The expert estimate of the fiber as a stock for the making of the finest paper, including banknote paper, has been so enthusi- astic that it might be well to devote attention to the breeding of some of the spineless Opuntias with an eye to the development of the fiber, so that this by-product of the plant may become of value as a source of paper stock; also for the making of leather board. One striking peculiarity of the Opuntia fiber is that it is bleached without any preparation. When the pulp is removed, the remaining fiber is white, and ready for use without necessitating the usual process of bleaching. So the Opuntia which develops its enormous weight or tonnage of forage and its abundant supply of food for man in the early stages of its growth, will subsequently, without relinquishing its original function, produce supplies of fiber that may be of value. The rapidity and growth of the plant would insure the production of such quantities of material as to give it a certain im- portance even if it could be grown only on arable lands; but the quantity is at best relatively small. That it can be grown also on many other- wise waste places is obviously an additional merit of the first grade. THE CACTUS 159 A SUMMARY OF QUALITIES Let us, then, in conclusion, summarize briefly the qualities that give the new spineless Opun- tias economic value. In so doing I may refer to two or three subordinate uses to which the plants have been put that have not been specifically mentioned in the preceding studies. Here is the list: First: The new spineless Opuntias supply abundant quantities of fresh fruit that is unique in form and color, of superior flavor, of sure crop, and of good shipping qualities. Delicious jams, jellies, and sirups may be made from the fruits; and its juices are used for coloring ices, jellies, and confectionery. Second: The slabs or so-called leaves of the plant supply an unprecedented amount of forage for stock of all kinds and for poultry. Third: The young slabs make excellent pickles, and are good and wholesome food when fried like egg plant. They are also boiled and used as greens, and may be prepared with sugar to produce a sweetmeat similar to preserved citron. Fourth: The leaves are extensively used in Mexico and elsewhere for poultices, and as a 160 LUTHER BURBANK substitute for hot water bags — the thornless kind being naturally preferred! Fifth: The abundant plant juices contain a mucilaginous substance that is used to fix pig- ments, and which in time will be put to many other important uses. Sixth: The thorny varieties are used for hedges or fences, as well as for ornament, and even to protect the thornless ones. No animal of any kind will undertake to pass through one of these thorny hedges. In regions subject to the drift- ing of sand they serve an important purpose as barriers. Seventh: The fiber of the plant makes an admirable stock for the manufacture of paper, but not as yet in large quantities. Eighth: In general, the adaptability of the new Opuntias to the arid region gives assurance that vast semiarid regions of the globe will be made habitable and productive, although hither- to they have produced scant if any vegetation of economic value. Without looking further it must be clear that a plant having such qualities may be regarded as the most neglected of vegetable products. Owing to its spines, the cactus has been regarded as an enemy of man. Now that its spines are removed its good qualities will in due course be appre- THE CACTUS 161 elated. Should their present promise be fulfilled, the giant spineless Opuntias may make vast areas that heretofore have been relatively sterile among the productive regions of the world. They may supply fodder for unlimited num- bers of cattle, that will give cheaper food to the masses, and conspicuously decrease the cost of living. They may even avert famines in regions that have hitherto accepted the recurrence of starva- tion years as an inevitable visitation. And even should the future benefits that ac- crue from the new spineless Opuntias realize but a fraction of their present promise, these plants might still be entitled to a foremost place among the forms of vegetable life that have been introduced, or improved, for the service of man within the historical period. THE HEREDITY &F SPINELESSNESS Before taking leave of the spineless cactus, it may be of interest to make further inquiry as to the hereditary bearings of the condition of spinelessness. We have seen that the new spineless Opuntias were developed by a long series of experiments in hybridizing and selection, in which use was made of individuals that showed a propensity 6— Vol. 6 Bur. 162 LUTHER BURBANK to depart from the spine-bearing custom of their race. Among the seedlings of these plants some were found to be much less spiny than others, and it was ultimately possible, by selecting among literal millions of specimens, to develop races absolutely devoid of spines and spicules, as we have seen. It would not have been unreasonable, perhaps, to expect that the spineless races thus developed would breed true to spinelessness ; particularly when we recall that the thornless blackberry, if inbred, produces only thornless progeny. But if such an expectation were entertained, it would be doomed to disappointment, for the spineless cactus does not breed true. In point of fact, there may be found among the seedlings of a spineless variety plants that fairly bristle with spines, rivaling in this regard the best protected of their wild ancestors. Obviously, then, the condition of spineless- ness in the cactus has quite different relations in the scheme of heredity from the conditions that govern spinelessness in the blackberry. In the latter case, as we have seen, the spineless condi- tion appears to be recessive, and the thornless individual is as free from tendency to produce thorns as if its entire coterie of ancestors had been perfectly smooth-stemmed. The individual THE CACTUS 163 spineless cactus, on the other hand, retains the factors for spines in its germ plasm, to make their influence tangibly felt in a large propor- tion of the offspring. Nevertheless, it does not appear that the con- dition of spininess acts as a simple Mendelian dominant. On the contrary, it appears that the hereditary conditions that govern the spiny con- dition in the cactus are very complex. The best interpretation would seem to be that there are multitudes of factors for spicules and spines, variously blended in the germ plasm of any given individual. The spiny condition, on the whole, tends to be dominant to the spineless condition, because the spines are a relatively late develop- ment in the history of the evolution of the cac- tus tribe. But doubtless the period in question was an exceedingly long one, covering many thousands of cactus generations, during which the plants were becoming better and better protected; and each stage of such development may be thought of as having its hereditary factors in the germ plasm, capable of acting independently. Thus it is that in the same fraternity some seed- lings are exceedingly spiny, while others have a comparatively small number of spines, and a few may be absolutely spineless. Thus, also, is A CACTUS-SLAB FAN The fibrous portion of this fan repre- sents the fiber of a cactus leaf from which the pulp has been removed. In the young slab, these fibers are tender and fragile, but they become tense and rigid in the old slabs. An excellent paper may be made from this fiber, and it will doubtless, in time, be put to many other economic uses. THE CACTUS 165 explained the fact, to which attention has been called, that the plants that are altogether spine- less may still be provided with minute spicules. Such minute spicules were, perhaps, the first defensive mechanism to be developed in the evo- lution of the cactus tribe, and they have back of them such numberless generations of heredity that they hold their own with exceptional per- sistency. In dealing with the spines and spicules of the cactus, then, we must consider that we have to do not with a single hereditary factor or two, but with a multitude of factors. Now our ear- lier studies have taught us that where several or many hereditary factors are in question, the probability that they will all be combined in any given way in a single individual decreases at a geometrical ratio. We found, for example, that where ten hereditary factors were under consideration, the probability of their combina- tion in a predicted manner was only one in something over a million. In the case of the cactus the factors for spininess doubtless number far more than ten; from which it follows that the probability that any given seedling will have germ plasm absolutely free from any of the fac- tors for spininess is much less than one in a million. 166 LUTHER BURBANK This explains why it was necessary, in our experiments at Santa Rosa, to plant the seeds by literal millions, and to select persistently among uncomputed multitudes of seedlings. Fortunately the spiny condition reveals itself almost from the outset, so that it was possible to weed out the vast majority of all the seedlings, retaining only, perhaps, a stray dozen or so from among the legions. As the experiment proceeded, however, it was gratifying to note that in succeeding genera- tions there was an ever-increasing proportion of spineless seedlings. This suggests that some of the factors for spininess were being dropped out of the heredity of the selected plants. Obviously this seems to augur that should the experiment be carried forward through a sufficient number of generations, the time will probably come when all factors for spininess will have been eliminated from the germ plasm of the selected opuntias; in which case they will then breed true to spinelessness from the seed. This prediction finds further warrant in the fact that the newest races of spineless opuntias show a far more pronounced abhorrence — if the phrase be permitted — of the spiny conditions than did the earlier ones. It was observed that the first spineless opuntias to be developed THE CACTUS 167 at Santa Rosa, although remaining perfectly smooth under ordinary conditions of cultivation, had, nevertheless, a tendency to revert to the spiny condition if placed under disadvantageous conditions — say in arid soils, unwatered and un- cultivated ; a state comparable to that of the wild spiny progenitors. This tendency to reversion is in itself highly interesting from the standpoint of the student of heredity; being comparable, perhaps, to the observed tendency of some plants, on rare occa- sions, to form what are termed bud sports. As a rule, plants grown from cuttings or roots or buds reproduce absolutely the characteristics of the parent form. We have seen this illustrated over and over in endless numbers of cases, from orchard fruits to Shasta daisies. This rule holds true of the cactus, as has been pointed out in re- cent chapters. You may produce an entire field of spineless opuntias of any given type, as off- shoots of a single slab. But of course no plant is free from the power of environment, and no one needs to be told that the choicest orchard fruits, for example, will fail signally to justify expectations based on observations of their parent forms, unless they are given proper conditions of soil and cul- tivation. Cuttings or buds of the Baldwin 168 LUTHER BURBANK apple, for example, will produce but perverted replicas of the original Baldwin if grown in an arid soil, deprived of moisture, and shaded by other trees. Under such conditions, the choicest varieties of apples tend to revert more or less to the primitive type of the wild ancestor of very remote generations. Similarly the spineless Opuntia may tend to revert to the wild forms if placed under prime- val conditions. In a stony, arid soil, deprived of moisture, it may not only be stunted in growth, but it may show a propensity to revert to the spiny condition. Such, at any rate, was the case with the earliest spineless opuntias that were produced at Santa Rosa, but this tendency is wholly obviated in the newer ones. As the experiment has gone forward, however, the condition of spininess has been more and more subordinated, as just related; the proof being not only that the individual plants are absolutely free from spines and spicules, but that more and more of their seedlings are found to be spineless. And this elimination of the hered- itary factors for spininess is so profound and deep-seated that the newer or more recently de- veloped varieties of spineless opuntias appear to have lost altogether under all circumstances the capacity to revert to the spiny condition. Even THE CACTUS 169 under the most adverse conditions of soil and climate, they remain absolutely smooth. One other step of progress and, we may confidently predict, the factors for spininess will be so com- pletely eliminated from the germ plasm that the spineless opuntias will breed true from the seeds. Even then it must not be expected that the seedlings in any given case will reproduce all the good qualities of the parents ; any more than the seedlings of cultivated varieties of apple or pear or peach will duplicate the qualities of their parents. We have seen that the seedlings of the thornless blackberry are not precisely like the parent form. But they all are thornless. Such will be the case, ultimately, with the spineless opuntias. And it must be obvious that when this condi- tion is attained, the experiment of developing the opuntias in any direction will be greatly facilitated. With many varieties of spineless opuntias in hand, each one absolutely free from the tendency to revert to the spiny condition, we shall be able to carry forward experiments in crossbreeding and selection through which any desired quality may be accentuated and developed. At the present time, for example, the spineless opuntias are somewhat lacking in protein con- 170 LUTHER BURBANK tent. Their foliage value is not quite what it would be if the protein content could be in- creased. And there is no reason to doubt that such increase may be possible through selective breeding. Already the developed spineless opun- tias exceed all other plants in their capacity to produce an enormous quantity of forage. Through selective breeding their preeminence may be still further advanced in that each indi- vidual slab may be given enhanced food value. And the qualities of other useful chemical sub- stances in the cactus may similarly be increased in selective varieties. Heretofore the development of the cactus has been along the lines of spinelessness, size, and productiv- ity; the future will see a marked improvement in the percentage of its food constituents, especially in its fruits. OTHER USEFUL PLANTS WHICH WILL REPAY EXPERIMENT TRANSFORMATIONS AND IMPROVEMENTS WAITING TO BE MADE A STORY is told that, if true, gives a former Mikado of Japan an important place among plant developers. The Mikado, so the story runs, \vas riding about the country — as was once the custom — to inspect the crops, and he espied a bunch of rice which seemed to be earlier and more productive than others in the same field. Evidently aware of one of the fundamental principles of plant breeding, the Mikado directed that the seed from this hill of rice should be care- fully preserved and sown by itself the next season. From this seed, if we are to believe the legend, a superior new variety of rice was pro- duced in Japan. Whatever the authenticity of the story, the fact that it is told gives evidence that some of • 171 172 LUTHER BURBANK the fundamental principles of improvement of plants by selection are widely recognized in the land of the Mikado. But this, indeed, is a proposition that scarcely needs demonstrating, considering the curious variety of flowers and fruits that have been developed there. That the revered name of the Mikado should be associated in popular legend with the perfecting of the rice is to be inter- preted, I suppose, as an evidence of the impor- tance of this grain to the people of Japan, rather than in any literal sense. Rice is to the Oriental people what wheat is to the people of the western world, and it is natural that folklore should associate the perfecting of this most important of foodstuffs with the most sacred office of the ruler who is regarded as the Father of his people. RICE AND ITS IMPROVEMENT Mention of the perfecting of special varieties of rice implies the existence of different varieties of this grain. In fact, rice is a very variable plant, and one that is therefore susceptible of great improve- ment. There are many varieties of rice grown in the Orient. There is, for example, a variety that has a very pleasant aroma when cooked. PLANTS FOR EXPERIMENT 173 There are. varieties that grow on the upland, the culture of which is similar to that of wheat or barley; notwithstanding the fact that rice is usually thought of and grown as a marsh plant. These have recently been introduced into the cotton regions of the south, and I am told that in some regions they are supplanting the cotton crop. Also rice in certain sections of northern California is lately being grown by the million bushels annually. Some botanists have classified no fewer than six species of rice, and there are many hundreds of varieties, variation seeming to be no more unusual than with wheat, oats, or barley. It is only the relative unfamiliarity with rice of the western world that has led to the supposition that one kind of rice is like another. At the Panama-Pacific Exposition of 1915 over two hundred varieties were on exhibition from the Philippines alone. Our estimate of the grain is somewhat analogous to our estimate of the Oriental peoples. The casual western observer thinks that all Japanese and all Chinamen look a good deal alike; but to the practiced eye there is nearly as great diversity among them as among European races. 174 LUTHER BURBANK The upland rices show their derivation by requiring somewhat moist soil, and they are not grown to advantage in California, except in the moist retentive soils of the Sacramento Valley, and to a certain extent in the Coachella Valley. In the former region, however, the growth of the upland rice has proved to be exceedingly profitable. I have tested different kinds of rice here on several occasions, but the results were not such as to induce me to continue its culture, the condi- tions not being favorable. But the fact that varieties of rice have been developed that grow on the upland gives assur- ance that further development may be possible in the direction of adapting the plant to general cultivation on lands suitable for growing of other cereals, as already demonstrated in the South. Doubtless a good deal can be done also to make rice a hardier plant through selective breeding; and few attempts at plant develop- ment could have greater importance, for rice is a grain hardly inferior to wheat itself in nutri- tional value, and one that might be cultivated far more extensively in this country, to very great advantage, My own experiments have had in view the possibility of the development of the American PLANTS FOR EXPERIMENT 175 wild rice (Zizania aquatica) of the northern lake regions. This, however, is not a true rice, being classified as Zizania, while rice belongs to the genus Oryza. Some twenty years ago I desired to undertake such an experiment, and sent to many places in the United States to get seed of the best varieties. But although I secured seed of the wild rice, my experiment, I regret to say never got beyond the preliminary stages, because the seed would never germinate. After testing it in successive years I was con- vinced that the seed of the wild rice must be gathered fresh for planting. For its improve- ment it would be necessary for men with boats to watch individual plants, and gather seed for immediate planting. The fact that the plant grows in the water accounts, no doubt, for this unusual quality of the seed, as it will not germinate after once being dried like other grains. It grows always in standing water, and is generally collected by the Indians, who are extremely fond of it. They go out in canoes when the wild rice is ripe, and bending the rice over their canoes thresh it from the heads into the boat. During the last year a well-known San Francisco grain firm had col- lected some of the wild rice and kept it moist, and they expect to make a successful introduc- 176 LUTHER BURBANK tion of it in this State. Conceivably a commer- cial variety of importance might be developed that would be better adapted to the American climate than the oriental rice. I hope even yet to be able to make the experi- ment. Failing this, I trust that some one else will take the matter in hand. SOME NEGLECTED GRASSES If my work with rice has been only tentative, there are almost numberless allied grasses with which I have experimented on a comprehensive scale. Indeed, I have raised, at one time or another during the past forty years, almost every grass that has economic importance, and many never supposed to have value. Among these several fine varieties have been introduced through Cecil Rhodes of South Africa, which proved enormous croppers in moist, warm regions of this State. Some of these I have grown extensively year after year; others only for a single season, for the purpose of obtaining variation in some useful direction. My work with the familiar giant grasses, Indian corn, sorghum, and teosinte, and with the equally familiar small grains, has already been detailed. I refer here to other grasses that are PLANTS FOR EXPERIMENT 177 less widely known to the general public, includ- ing some that are rarely seen even by the agri- culturist. My experimental work with these various grasses has been as diverse as the qualities of the plants themselves. In some cases I have selected for increase of productivity, and in others for increase of chem- ical constituents, or for beauty of plume, or ability to resist drought or frost or wind or mois- ture; or, again, for compact growing or for ability to spread, or for length and breadth of leaves, or for striping of foliage. The grasses are so numerous and so diversified that there is opportunity for almost indefinite choice as to lines of development, and there are few other groups of plants that offer greater possibilities. To casual inspection, to be sure, most of the grasses seem rather uniform, commonplace, or unattractive. They lack the beautiful flowers that so many other plants present, and their forms, if almost universally graceful, are for the most part lacking in picturesqueness. Add that the grasses present great difficulties to the botan- ical student because of the minuteness of their flowers and the vast number of species more or less closely related, and you may readily under- 178 LUTHER BURBANK stand why this tribe of plants is so commonly neglected by the amateur. But when we reflect that the family includes the most important producers of food for man and animals; and when we further reflect that there are doubtless many species still undevel- oped that might be brought into the company of economic plants, along with wheat, oats, rye, corn, and rice, it is evident that the grasses should be second to no other form of vegetation in their interest for the plant developer. Nor will the plants themselves be found to lack interest when once their acquaintance is ^ade in the right way. They vary in size from tiny sprigs of vegeta- tion to the giant pampas grasses, and to bamboos two hundred feet in height and six inches in diameter. We have already seen that their prod- ucts comprise not merely universal food and forage for domestic animals, and grains of ines- timable value, but juices (in the case of cane and sorghum) that are second in importance only to the grains themselves. We saw too that there are minor products, such as the panicle of the broom corn, that have no small measure of usefulness. And it is known to everyone that the stalks and straws of the various grasses have a wide range of utility in the manu- PLANTS FOR EXPERIMENT 179 f acture of numerous articles of everyday use, in- cluding the mats beneath our feet and the hats on our heads, as well as the food from the tubers of the nut grass. Whereas it cannot be said that a family of plants that is thus comprehensively in the service of man — having had, indeed, a most important share in the development of civilization — has failed of recognition, yet it remains true that there are perhaps thousands of grasses that are almost surely susceptible of great improvement, from the human standpoint, to which very little attention has been given by the plant developer. These present an inviting field for further development. I shall offer in the succeeding pages sugges- tions as to a few of them, drawn from my own experiences. To attempt to deal with all the neglected grasses comprehensively, and to point out every individual possibility of useful de- velopment, would require volumes rather than paragraphs. A NEW BREAD-MAKING POSSIBILITY One of the grasses upon which I worked for several years was what is known in the catalogues as "Idaho brome grass," classified as Bromus inermisj or Bromus giganteus. PAMPAS GRASS I have experimented very extensively with various types of pampas grass, developing some interesting varieties by hybridization and selection. The pampas grasses are not as popular now as they were a few years ago, but they are no less beautiful than they were when they had their heyday of popularity. PLANTS FOR EXPERIMENT 181 I chose this plant on account of its extreme hardiness. It resists drought remarkably, and is very productive. My original seed was received from Montana. I have also grown extensively other species of the same genus, to the number of four or five. My main object was to produce a variety that would yield more forage. Seeds were sown thinly in boxes in the green- house, or in plots out-of-doors. Selection was made when the plants were about half an inch high, and before they had put forth their second leaves. At this stage a fairly correct judgment can be formed as to which plants will be rapid growers. In general, the plant that will ultimately tower above its fellows is found to show superiority in its earliest stages. By selecting the plants that seem to give most promise, and planting these in rows where the soil is practically the same throughout, it is not difficult to discover the most rapid growers and to weed out the others. The brome grasses are much more variable than is commonly supposed even by those who are familiar with them. In fact, even within the same species, it is difficult to find two plants that are precisely alike. Some have broad leaves, and some narrow, and the leaves may be variously 182 LUTHER BURBANK curled or twisted, as well as variant in color, some being much darker than others. Some specimens go to seed without producing much foliage; others grow abundant foliage but are tardy of seed production. The plants that show this propensity to pro- duce foliage rather than seed are, other things being equal, the ones to select, except from the viewpoint of the seedsman, who does not appre- ciate this kind of grass. I have aimed to get a variety with broad, rich, dark green leaves, and found it comparatively easy to develop such a variety. Notwithstanding the great variation shown by the individual bromes, I found that varieties once specialized tend to come somewhat true to type in the succeeding generations. Therefore it is a very easy matter to improve the different species of bromes. By far my most interesting experiment with plants of this genus was made about twenty years ago with a plant, seemingly of the species known as Bromus mollis, that was found on the edge of the Santa Rosa Creek, about one mile east of Santa Rosa. This wild grass bore a long head of rather plump seeds that were without awns, and that suggested to my mind the possibility of the de- velopment of a commercial grain. The seeds PLANTS FOR EXPERIMENT 183 were planted and carefully cultivated, and the best seedlings were selected for propagation, with the result that in the course of a few years a variety was secured in which the size of the seed head was markedly increased, and in which the individual grains are very much plumper than the original one. The grain seemed so promising that I tested it by grinding it. It was found to produce an ex- cellent flour with a slight yellow tinge. When prepared and baked in the ordinary way, it made a very good bread. I was quite sure that a grain of good commer- cial value could be produced by further selective breeding from the seed of this brome. But I had only a small quantity of seed, and as other mat- ters took my attention I neglected to plant it for two or three seasons; and when it finally was planted it failed to germinate. So the experi- ment came to an end in unsatisfactory fashion, yet not without offering interesting suggestions as to the possibilities of development of this and other plants of the tribe. Unfortunately I was not quite sure as to the exact species of brome that furnished the material for this experiment. Moreover, I have not found another plant that showed the same exceptional qualities of seed with which a new line of inves- 184 LUTHER BUHBANK tigation might be begun. The one mentioned was discovered only after careful inspection of more than twenty-five thousand samples. But the finding of one sufficiently proves that there must be others to be found if we search widely enough, so I record the experience as a stimulus to further search and investigation with a tribe of grasses represented by numerous other species that are familiar enough in fields and waste places, but which at present are regarded as weeds rather than as friends of the agriculturist. SOME CULTIVATED GRASSES Some of the most striking results I have ever seen in the way of development of grasses were obtained with the perennial known as the Sweet Vernal Grass (Anthoxanthum odoratum). This grass is exceedingly variable. A few years ago I raised about fifty thousand plants in boxes. From the seedlings the largest and the smallest were selected; the broad-leaved and the narrow; the dark green and the light green; and those showing any other striking peculiarity. By planting the individuals that presented these diversified traits in plots by themselves, and carefully selecting their seed, races of perennial PLANTS FOR EXPERIMENT 185 sweet vernal grass were obtained presenting the widest range of characteristics. Thus varieties were produced that would bear almost no seed, and others that bore seed abun- dantly, some which increased from the roots with great rapidity, and others that increased very slowly. From among the thousands of plants that were raised and scrutinized, I found two or three that would grow more than one hundred times as fast as the smaller ones. Not only was this startling increase in vigor of growth shown at the outset, but it was continued at the same rate season aftei; season, where the plants were raised by division. The differences in the growth of the various plants could be detected almost from the moment when their tips appeared above the soil. But, of course, the selection involved very close scrutiny, and I sometimes spent hours at a time over a box containing perhaps ten thousand to twenty-five thousand plants, selecting two or three that outgrew all others. Here, as with the other grasses, rapid growers in the boxes were almost invariably rapid growers throughout. The seed of the strongest growers was preserved, and the experiment was carried forward with the expectation of developing races of perennial sweet vernal grasses that would not only show 186 LUTHER BURBANK improved quality of foliage, but an enormously enhanced capacity for growth. The practical value of such an experiment as this, from the standpoint of the agriculturist, will be obvious. That such variations may occur among plants from the same lot of seed gives a clew to the ob- served differences of neighboring forage fields. It is clear that the diversities that are usually ascribed to differences of soil may be due in part to different strains of seed. The value of devel- oping a forage grass to its fullest possibilities of productivity is too patent to require comment. That one plant could be made to grow, and to maintain throughout life a rate of growth one hundred times in excess of other individuals of the same species, is a fact that should be stimu- lative to any experimenter who thinks of working with the grasses, and that is certainly of signifi- cance to the cultivator of forage plants. I have experimented extensively also, and with interesting if less picturesque results, with the millets, the rye grasses, and orchard grass, as well as with numberless more or less conspicuous varieties. My work with orchard grass (Dactylis glome- rata), which was only neglected in the past few years, included an interesting experiment grow- PLANTS FOR EXPERIMENT 187 ing out of the discovery several years ago of a seedling that produced leaves much longer than the ordinary, as well as a large, strong stalk, and a large cluster of blossoms different in form from those of the ordinary orchard grass. The plant was so individual that it could be distinguished at a considerable distance by its greater size and anomalous appearance. The seeds of this plant were found to follow the variant type of their parent somewhat closely. The type has not been entirely fixed, but is worthy of further attention. In a few more sea- sons, according to present indications, it will be so fixed as to produce regularly from seed a type of orchard grass that would nearly double the growth of the ordinary variety. Another variable grass that I have cultivated extensively in recent years, for observational pur- poses rather than commercial varieties, and from which new varieties are being developed, is the species known as Agrostis Fontanesi, recently introduced from Algeria. From the same plant have been produced seedlings with broad spread- ing panicles, others with compact spikes, and yet others with beautiful spreading spikes. On sow- ing seed from different panicles it was found that the tendency to compactness or looseness of head was transmitted or accentuated, so that 188 LUTHER BURBANK widely differing varieties were developed in the second generation from seed of a single plant. Some similar results with Bermuda grass (Cynodon dactylon) were obtained. With this I have experimented from time to time during the past twenty years, more particularly in the effort to produce a lawn grass which would fulfill the function in arid regions that the blue grass fulfills in moist climates. I have found that this grass varies even more than most others do from seed, and by selection was able to produce dwarf varieties, or, on the other hand, the tallest and largest-growing ones ; also varieties with broad leaves and others with narrow leaves. There were plants that came up thickly and made a compact sod, not having the wild running habit of the original variety. And others that sent out runners and spread so rapidly that in a single season one plant would cover the ground for ten feet in all directions. These extraordinary diversities were shown among plants selected from the same lot of seeds. In all there were at least twenty quite distinct varieties developed, each marked by one or more obvious and striking peculiarity. But as Bermuda grass is commonly regarded as a weed, none of these were introduced. PLANTS FOR EXPERIMENT 189 ORNAMENTAL AND USEFUL GRASSES At various times I have taken great interest in the ornamental grass commonly known as pam- pas grass, the plumes of which were at one time in great demand. The form of pampas grass that is most grown in California is that known technically as Corta- deria argentea. The plumelike panicles of this grass are familiar ornaments everywhere, and were, in the time of their greatest popularity, articles of some commercial importance. The plumes to be preserved in the best way should not be allowed to come out of the sheath before drying. The long stems, with several leaves attached, are cut just as the tip of the plume begins to show. The leaves are stripped off, and the stalk is placed in the bright sunshine, preferably standing, but more commonly spread on boards or on the ground. Prepared in this way, the panicles do not shake to pieces. They assume the aspect of silky plumes, which are given a peculiar fluffiness and brought to perfec- tion by being placed in a hot oven for a few moments. I have raised perhaps a hundred thousand seedlings of various pampas grasses, and have crossed them extensively. 190 LUTHER BURBANK There is no difficulty in effecting cross-ferti- lization, provided, of course, the two species bloom at the same time. Pollen from the ripe male plant is simply dusted over the pistillate flower. The female plant is the one that is useful for ornament, the male plant having a smaller and coarser plume, which is never silky or fluffy, and which readily falls to pieces under any treatment. There are pampas grasses, however, that have both staminate and pistillate flowers in the same blossom, and, of course, these cannot be cross- fertilized with such facility. My most interesting experiments have had to do with the crossing of a pink variety of pampas grass that bears both staminate and pistillate flowers, with some of our finest large white varie- ties. These plants crossed readily and many thousand seedlings were raised. A large pro- portion of the seedlings were plants bearing both stamens and pistils like the pink parent. Very few were female plants, and therefore bearers of good plumes. Even when the plumes were produced, they were usually not as large as those of the white parent, and many of them were smaller even than the small plume of the pink parent. This is easily accounted for by the fact that the great PLANTS FOR EXPERIMENT 191 white plume had been produced through artificial selection, and therefore its characters were not as well fixed as in the wild type. An interesting feature of this experiment was that the pink color seemed to appear oftenest on the staminate plants and not on those that bore both stamens and pistils. This gives a suggestion of the element of sex selection in heredity, which is seldom observed in plants, although common enough among animals. A further evidence of this was seen in the fact that I was never able to fix the color so thoroughly on the female plants as on the male. The pampas grass is multiplied by division, so that there is no difficulty about the multiplica- tion of a new variety. The new varieties do not usually come true from seed. But this is of no importance, inasmuch as a single plant may be1 so multiplied by division as to produce probably fifty thousand marketable plants, on good soil, in the course of two or three years. SOME MISCELLANEOUS IMPROVEMENTS From among a great variety of experiments looking to the improvement of farm and forage crops, I will select only three or four additional ones as offering further suggestions. 192 LUTHER BURBANK An interesting anomaly with which I have experimented is a hybrid form of the wild oat. A field of the second generation of these hybrid oats furnishes one of the most interesting studies of variation that has come under my observation. Inspecting a field of these oats, sown quite thinly, one finds on the same day some that are thoroughly ripe, while others are not yet in bloom. There is corresponding diversity as to the appearance of the plants, some having broad leaves and some narrow ones. Some of the plants are very tall, and others short and stocky. The panicles are of all forms and sizes. In a word, the hybrids vary in almost every way in which they could vary, and still be recognized as oats. It is obvious that such a variant type of oats gives opportunity for selection and development of new varieties. The tendency to vary as to time of ripening has peculiar interest, as suggesting the possibil- ity of adapting oats — and doubtless also the other cereals — to different climates, or even of the production of different varieties in the same locality, which, by ripening at different seasons, would enable the farmer to avoid the ex- cessive rush of work that attends the harvest season. PLANTS FOR EXPERIMENT 193 Several years ago I worked quite extensively on buckwheat. This work consisted largely of selecting the larger, plumper, and lighter- colored kernels. The work was carried on with both the common buckwheat and the Japanese species. A certain amount of crossing was done, but in general the plants were found to be so variable that nothing more was necessary than to select among the different forms that ap- peared spontaneously. Considerable though relatively slow progress was made in the production of a better quality of grain. The experiments were discontinued be- fore I began the extensive hybridization of the two species that had been contemplated. They could, of course, be crossed to advantage. Among textile plants, and plants of use in the textile industries, my most interesting recent ex- periments have had to do with the wild teazel, with the Chilean hemp, New Zealand flax, and many others that give promise of the production of a valuable fiber. The teazel, as is well known, has been an im- portant plant, inasmuch as its long-hooked burs are used for producing the nap on cloth, more especially the woolens, and no mechanical de- vice has ever been invented as a thoroughly satisfactory substitute. There are several dis- 7— Vol. 6 Bur. 194 LUTHER BURBANK tinct varieties of the plant and one of them is a weed that grows along neglected roadsides in California. Among any lot of wild teazels one may find a number of types, and it is not un- usually diffidult to fix these types by selective breeding. If it were necessary or desirable for any par- ticular use to make the hooks several times the usual length, or the burs themselves several times as large, this could easily be accomplished. My work had to do with some of the peculiar forms rather by way of experiment than with any practical idea. The forms worked with were those with vertical rows of hooks, instead of the spiral ones, and with varieties having extra large hooks at the base and double heads, The experiments were carried forward for sev- eral years for my own information and education and demonstrated that different kinds of teazel burs could be developed and fixed if desired. Possibly some modified form of teazel may be of use in a future industry. Hitherto it has not been known that modified forms were available. My experiments with hemp were conducted largely with an improved Chilean variety, but included also the use of seed from Japan, India, Russia and France, as well as from various parts of the United States. The experiments have PLANTS FOR EXPERIMENT 195 grown out of a suggestion that I made a number of years ago to a large Boston paper manufac- turer, to the effect that it seemed possible that the fiber of the hemp might be used as a substi- tute for wood pulp in the manufacture of paper. The experimental work is only at its begin- nings, but it seems to be of considerable promise, especially as to' improved size of plant, as a crossbred variety has been secured which out- grows all other hemps. The hemp, as is well known, is a dioecious plant, and it may be well to mention the simple but uncommon method of making crosses. All the varieties are first planted separately ; and only a few of the largest and tallest male and female plants of each variety are left to bloom. When the heads blossom, the tallest and best of each variety obtained from different sources are crossed with pollen of the tallest male plants. After two seasons of this selection and cross- ing of different strains from different countries, the varieties were combined by crossing, as be- fore, by selecting the largest and tallest plants, out of which a new race was produced of giant hemp. It was found that a hemp received from China and one from Chile were at first the two tallest and most rapid growers, but they were very shy 196 LUTHER BURBANK seed producers in this climate, especially the Chinese one. The variety which I produced from Russia was the most slender, and also the most dwarfed, so this had little to do with the giant hemp which was produced. Paper made from -the fiber of the hemp is found to be of good quality, and although not generally used heretofore must dertainly be more prized as other paper pulps become scarce. I mention this line of investigation here merely to suggest the wide range of opportunities that will become apparent for the plant developer when he has learned to cooperate with workers in the various industries. Hitherto we have been prone to take it for granted that all the valuable textile plants have been investigated and perfected. The newer studies suggest that there is still boundless oppor- tunity for progress, not only through the im- provement of the plants that have been utilized, but also through the introduction of species that have been ignored or neglected. WHAT TO WORK FOR IN FLOWERS AND How TO PROCEED O,NE of the plant developments that usually interests the visitor as much as almost any other has to do not with the flower or fruit of a plant but with the leaf. The plant in question is a species of "wild geranium" known as Heuchera micraniha, a native of the western coast, and the anomaly of leaf that attracts attention is the curiously crested, crinkled, and corrugated condition that makes the foliage of this plant quite unlike that of any other member of the tribe before seen. Indeed the new variety is so changed from its ancestral type that it is considered entitled to recognition with the varietal name cristata added to its technical title. Were it found growing in the woods instead of in a garden, it would per haps be pronounced a new species altogether. The story of this anomalous geranium will serve as well as another to introduce our studie 197 198 LUTHER BURBANK of the development of new varieties of flowers, even though the particular development under consideration has to do with the leaf of the plant, and not with its blossoms. The principle of its development is the same in its application to each part of the plant, and we shall see plenty of illus- trations of work with the flowers themselves before we are through. The wild geranium, of which the plant with the strange leaf is a modified representative, is a plant that normally has leaves some of which are rather decorative because of their slightly scal- loped margins, but which in general are quite plain. Some of the leaves are flecked with brownish spots, but the surface is quite smooth, as much resembling an apple or geranium leaf as any other. Even botanists have never taken special notice of any variation in the form of the leaf. There is, however, a marked tendency to vari- ation in different specimens, especially in the brown spots on the leaves, and the crimson shadings in the fall. A NEW LEAF BY SELECTION Several years ago, in examining some of these plants growing wild on a dry rocky ledge near Mt. St. Helens, I observed one that had leaves FLOWER POSSIBILITIES 199 slightly crinkled at the edges. This slight almost insignificant variation suggested a possi- bility that further variation in the same direction might take place if the plants were educated in the right way. So I transferred the plant with crinkled leaves to my home grounds, and in due time gathered its exceedingly diminutive black seeds. When the little plants that grew from these seeds the next season were carefully examined, I observed that some of them had leaves slightly more crenated or crinkled than the others. So even before the plants made much growth I was able to weed out half of them, as show- ing no evidence of progress in the desired direction. When the plants were still larger, but before any flowers appeared, about half of the remain- der were pulled up; and later in the season still others were discarded that had shown the crinkled condition at an earlier period but did tend to carry it well as they advanced in age. Of the many thousands with which I had started in the spring, only a handful remained toward seed time. And at last a single one among these was chosen as presenting leaves that from the point of view of the experiment were best. VARIATION IN COLOR AS WELL AS IN FORM These are different examples of our curiously crested "wild geranium" — a plant that has been so modified as to merit botanical classification as a fixed variety. It will be seen that there is marked variation in color as well as form. By selective breeding the color variations are being fixed just as the crested condition of the leaf has been. The modification shown has been effected by selective breeding alone, without hybridization, from the smooth, flat leaf of the common wild Heuchera. (One-half life size.) FLOWER POSSIBILITIES 201 This single plant was allowed to mature its seed. The plants that grew from this seed, repre- senting now the second filial generation from the original wild plant, were treated in precisely the same way. But it should be recorded that there was great improvement in this second generation. Now three-quarters of the plants showed leaves that were markedly crinkled. Each plant produces thousands of seeds, and progress was relatively rapid, as great numbers could be produced from which to select. By process of elimination, the one best plant was again selected and its seed preserved. In the next generation practically all of the plants produced the curiously modified form of leaf. In the fourth generation, as before, very large numbers of plants were raised that there might be wide opportunity for selection. Now all the plants presented the crinkled leaves, but there were of course individual specimens that ex- celled, and these were chosen to the exclusion of the others. Their progeny bore uniformly crinkled leaves of the most pronounced type, and they constitute the new species Heuchera cristata as it grows to-day. 202 LUTHER BURBANK The remarkable crinkled and convoluted leaves are so interesting that they are sometimes preserved by electroplating, to be used as orna- ments. They give the plant a very curious and individual appearance, and present a striking illustration of what may be done, by mere in- breeding and systematic selection, to develop and accentuate a plant characteristic. No one who casually observed the old parent form of the plant and the new modified form growing side by side would be likely to suspect that the two belong to the same species. Yet an examination of the flowers would show that these are identical, for in making the successive selec- tions I paid attention to the leaf exclusively, and did not seek in any way to modify other portions of the plant's structure. To the person who has not had experience in plant development, probably the most remark- able feature of the entire matter is the compara- tively short time required, and the few genera- tions involved, in producing what is a remarkable transformation — the most conspicuous transfor- mation in a leaf that has ever been produced. The nearest approach to this structure is seen in the leaf of the Rex Begonia called Erdody, It may seem further remarkable that a transforma- tion of such significance could be effected in a few FLOWER POSSIBILITIES 203 generations by selective breeding without the aid of special experiments in hybridizing. But this case is presented here at the beginning of our special studies of flower development, largely to emphasize the possibility of modifying even so fixed a structure as the leaf of a plant merely by selection of individual speci- mens that vary in a given direction for a few generations. I would emphasize, however, the necessity of operating with a large number of specimens if one is to obtain the best results in the shortest practicable time. The account of the experiment just given makes it clear that by having large numbers to choose from, I was enabled to discard numberless specimens that would have answered the purpose fairly well in favor of the single specimen that showed the desired quality modi- fied preeminently. THE QUESTION OF HYBRIDIZING This case, as was said, illustrates the possi- bility of producing striking results in plant modi- fication by mere selection without hybridization. No effort was made to induce the plant to vary more rapidly, first because there seemed no neces- sity for stimulating it to further variation, and secondly because no plant was at hand which 204 LUTHER BURBANK presents such a character as the one I wished to develop. Yet it should not be overlooked that there was an element of pollenizing involved, even though the pollenizing was not done by the plant experi- menter. This is almost axiomatic because of course the plant would have produced no seeds unless its pistils had been pollenized. All that I had done, to be sure, was to trans- plant the original geranium to a place where it was isolated from any other plants of its species. But such isolation in itself served to provide that the pistils of the plant should be fertilized with pollen from its own flowers. In other words, by isolating this Heuchera with crinkled leaves it had been determined that the pollen and ovules from the selected plant should combine to produce the seed germs for the next generation. And in so doing I made sure that both hereditary strains — that brought by pollen and that brought by ovule — should have the same hereditary factors, because they were borne on the same plant. This, then, was a case of inbreeding or "inten- sification" which has been mentioned previously. It was as far removed as possible from the hybrid- izing experiments we have witnessed in which species of widely different type, say the straw- FLOWER POSSIBILITIES 205 berry and the raspberry, were interbred. In such a case as that the pollen and the ovule bring groups of hereditary factors that are widely divergent. And even in the usual cases of cross- fertilization within a species, where pollen of one plant is brought to the pistil of the flower of a neighboring plant, there is a certain opportunity for the mingling of diverse hereditary fac- tors, inasmuch as no two plants are precisely alike. But in the case of our Heuchera, the flowers were self- fertilized, or at most the pollen from one flower was transferred by an insect to the pistil of a neighboring flower on the same stalk, and thus it was arranged that both hereditary strains should be as nearly identical as is possible. In the essential matter of the form of leaf, the hereditary factors brought by the pollen grains called for a leaf with crinkled edges; and the hereditary factors carried by the ovules had the same specifications. So there was the best pos- sible chance that the offspring would reproduce or accentuate the parent character. And yet the results show that there must have been a certain amount of diversity among the various pollen grains and ovules even of the single plant, inasmuch as the plants that grew from its seed were diversified in character. 206 LUTHER BURBANK About half of them, it will be recalled, did not present the crinkled leaf to any extent and were at once eliminated. And the other half exhibited the character in varying degree. Indeed, no two of them were precisely identi- cal, so we were justified in the conclusion that no two pairs of pollen grains and ovules brought precisely the same combination of hereditary factors together. When we consider the matter in this light, it will be evident that all pollenizing experiments are in a sense hybridizing experiments in one degree or another, inasmuch as they all of neces- sity bring together pollen grains and ovules that vary somewhat, even if only in very minor de- gree, in their hereditary factors. But it remains true — and indeed is too ob- viously true to require comment — that the case of the pollen grains united with pistils on flowers of the same plant (the case, that is to say, of the Heuchera under consideration) is that in which there is the least possible degree of varia- tion between the two sets of elementary factors that are combined. Therefore this process of so-called inbreeding introduces the least possible disturbing elements, and gives the largest probability of the reproduc- FLOWER POSSIBILITIES 207 tion of any given trait of the mother plant — which in this case is the father plant as well. The practical results have been already illus- trated in the production of this new race of Heuchera with leaves crinkled and corrugated in unique fashion so that they differ funda- mentally from the characteristic leaves of any other species or variety. The lesson to be drawn, then, from this experi- ment is that when we wish to modify a plant as to some particular feature of its anatomy, we shall proceed to best advantage if we (1) select an individual that shows the most marked de- parture from the normal in the desired direction of any that can be found; (2) isolate this plant so that its flowers shall be self-fertilized, or else hand-pollenize them; and then (3) follow out a similar course of selection of the best individual and self-fertilization of its flowers through suc- cessive generations until the maximum amount of variation in the desired direction has been pro- duced. It sometimes hastens the process to com- bine two or more of the best plants by crossing rather than to depend on a single one. We shall see in other connections, as indeed we have previously seen in our studies of many plants, that it is frequently desirable to stimulate variation by hybridizing plants that are diver- 208 LUTHER BURBANK gent, even plants of different species. But when an individual plant presenting an approach to the desired variation or modification has been found among the hybrid progeny, the successive steps of inbreeding and selection, through which the character is accentuated and fixed, will be carried out precisely as in the case of the little Heuchera just cited. Indeed, had we been able to take up the story of our little Heuchera a generation or two earlier, we might have found that such a crossbreeding experiment as has just been suggested had been performed for us by nature. It is highly prob- able that the original specimen with the tendency to crinkle leaves that was found in the woods was the product of a cross between plants, perhaps of the same species, that were individually some- what variant from one another. The plant grew on a cliff where very dry, very moist, and very unusual conditions of sun, shade, moisture, and soil prevailed, thus having current in its heredity a tendency to vary more or less, since heredity is only the visible effect of near and far en- vironments. Whatever the individual peculiarities of the parents of this particular plant, the individual that I found had leaves that were somewhat highly accentuated in a certain direction, being FLOWER POSSIBILITIES 209 thus proved to be the possessor of a somewhat unusual combination of hereditary factors for leaf formation. In a word, then, whereas the experiment with the Heuchera may be described as consisting ex- clusively (so far as the plant developer was con- cerned) of a series of selections, it really involved also the principle of the inducement of variation by unusual environment and the fixing of char- acters by inbreeding. And these fundamental principles of plant development must be involved, in one degree or another, in all successful experiments in the de- velopment and fixing of new types of plant or leaf, flower or fruit. Let us now witness the application of the same principles to the flower of the plant with refer- ence to the different characteristics of size and color and odor and modified petal or stamen or pistil that may be involved. PRODUCING A DESIRED FRAGRANCE INT THE FLOWER Probably no other characteristic of the flower is more highly prized than its odor. The sweet pea, the rose, and the carnation owe their popularity as much to their fragrance as to their color and form, yet there are numbers of PERENNIAL PEAS The Perennial pea has been greatly improved on my grounds during the past thirty years; flowers made much larger and in various new shades and more flowers to each truss. The plants, also, are earlier and more abundant bloomers. (About one-half size.) FLOWER POSSIBILITIES 211 very beautiful and popular flowers that are quite without attractive fragrance. There is no line of experimental work with flowers that should be more attractive to the amateur than the develop- ment of fragrant varieties of some of these odor- less flowers. And fortunately it is an undertaking that may be expected to produce very satisfactory results — as immediate, as striking, and as valuable re- sults as from any other plant experiment. In any group of odorless flowers you may have the good fortune to detect, if you search carefully enough, one that differs from its fellows in hav- ing at least a suggestion of fragrance. And if you will work in the right way with this individ- ual, you will be able to produce a race of per- fumed flowers, thus adding the finishing touch to a blossom which, however attractive otherwise, could not be considered perfect so long as it lacked this finishing quality. In an earlier volume we have heard the story of the fragrant calla. The reader will recall that this anomalous variety, known now as the Fragrance, was de- veloped by simple selection, along the lines just illustrated in the case of the Heuchera, with the difference merely that the characteristic borne constantly in mind was fragrance of the calla 212 LUTHER BUKBANK blossom instead of a peculiar conformation of leaf. By "line-breeding" and careful selection, I was enabled in a few generations to isolate a calla that has delicious fragrance while retaining all the other qualities of the flower unchanged. The seedlings of this selected calla are not in- variably fragrant. By careful inbreeding the fragrant calla could without doubt be made to breed true to the quality of fragrance. In the particular case of the calla, this is of no special importance, as the plant is propagated by division. But in plants that are propagated solely by seed, the fixing of the quality of fragrance would be essential. Fortunately it presents no special difficulties once a fragrant variant has been found. In a later chapter we shall learn of other ex- periments in producing fragrant flowers, and details will be given of the story of my fragrant verbena which was introduced under the name of Mayflower. The amateur who wishes to experi- ment along these lines may begin with almost any odorless flower in the garden. It is only necessary to search for delicate traces of fra- grance, and to learn to recognize nice shades of distinction among odors. Anyone can readily FLOWER POSSIBILITIES 213 detect the difference in fragrance in several varieties of the violet, rose, or carnation, for example ; and a still more highly cultivated odor sense enables one to notice differences in the fragrance of apple, peach, or almost any other blossoms from different trees or plants. So it is not necessary to confine one's ex- periments to flowers that lack fragrance alto- gether. Interesting results may be obtained by selecting among fragrant flowers those that have the most pleasing perfume, and developing those races that are especially notable for their special fragrance. The failure to give attention to the matter of fragrance sometimes leads to the cultivation of a special variety of fragrant blossom that has al- together lost its perfume. An illustration of this came to my attention not long ago when visit- ing the seed farm of the best-known seedsman in America. He called attention to his new varieties of sweet peas with great pride; and when I called his attention to the fact that a number of them were totally lacking in fragrance of any kind, he was not a little surprised. He was breeding sweet peas for immense size and brilliant colors and had succeeded, through selection, in producing very striking varieties. 214 LUTHER BURBANK But he had taken it for granted that all sweet peas are fragrant, and had before failed to ob- serve that these particular ones had no perfume whatever. Yet this seedsman is an expert who has been for nearly forty years in the business of grow- ing flowers. Like perhaps most others, he had taken it for granted that all varieties of fragrant flowers are fragrant. Series of experiments in crossbreeding would be necessary to reintroduce the perfume to these varieties that have lost this finishing quality. This case is mentioned to illustrate the fact that a given quality may be dropped out of a strain of flowers while another quality is being bred in. Also to emphasize the point that it is usually well to consider more than a single qual- ity in any breeding experiment. At least it is desirable to see that the qualities already present are not lost in the process of gaining new ones. PRODUCING NEW COLORS I am disposed to think that all shades of all colors that can be produced by blending of the primary colors are within the possible attain- ment of any flowering plant. The obvious fact that certain species, and in, some cases whole genera, produce only red flow- FLOWER POSSIBILITIES 215 ers, others only blue ones or yellow, does not by any means prove that the plants in question have not the capacity to produce flowers of quite different color. We have seen that the colors of wild flowers have been given them by insects. We have noted that the bright colors— reds, orange, blues— have been assumed by flowers that flourish in the day- time and seek association with the bees ; and that the flowers that consort with night-flying insects, such as moths, are almost universally decked in white or pale yellow — hues that make them far more conspicuous in the twilight than the most brilliant scarlet flower would be. Most wild flowers of a given species are of a single color, or of a definite arrangement or com- bination of colors. Bees and other insects have learned to distinguish this characteristic color or combination of colors, and to go with certainty from one flower to another of the same species, thus unconsciously serv- ing the flower well by cross-pollenizing its blossoms. I have often thought how confusing it must be to the bees on coming to our gardens to find flowers that perhaps are familiar as to perfume and form now arrayed in a dress of unfamiliar hues. But bees, like flowers, can adapt them- 216 LUTHER BURBANK selves to their environment. They soon adapt themselves to the new colors and combinations of colors that man has given the flowers, and they go about their task with undiminished celerity and certainty. Recognition of the fact that wild flowers have been given their colors by the insects through the slow process of natural selection (in which flowers that lack the color were not visited by the bees and hence produced no offspring; whereas the flowers that did produce the color were fertilized, and perpetuated their kind, and reproduced their qualities in abundant progeny) gives us the clue to the way in which we may go about the development of a new color or color combination in a flower. Suppose, for example, we desire to change the flower from white to yellow. How shall we go about it? First of all, we must produce thousands of seedlings from our white flower. Let them blos- som, and then search among them with the keen- est eye to detect a trace of yellow color — which is found more or less in all white flowers — in the flowers of any single plant. You are almost certain, if your scrutiny is suf- ficiently keen, to detect some plant that varies an infinitesimal shade from its fellows, showing at FLOWER POSSIBILITIES 217 least a trace of yellow; for a really pure white is extremely rare in nature. Select the seed of this plant; sow it next sea- son ; and repeat the process of searching. You will almost certainly be rewarded, if not in the first season, then in the second or third or fourth, by finding flowers that show very much more marked traces of yellow than the original flower. And even if the variation is not very striking at first, you will probably find that it tends to be accentuated after a few generations, especially in certain individuals. Each year you will discover flowers that are yellower than any of the preceding season; and presently you will have a blossom that is as yellow as you could desire, and a new race of plants that will breed true from seed. Placed side by side with the white flowers that were their ancestors, your new race will present a striking contrast. The fact that you have thus been instrumen- tal in virtually creating a new type of flower can scarcely fail to give you real satisfaction and pleasure. The fact that you have a flower such as per- haps no one else in the world possesses, and that this has been produced by intelligent and per- sistent effort, must be a source of quite justi- fiable self-gratulation. A YELLOW TRITOMA OR "RED HOT POKER" The wonderful new forms and colors which have been produced by crossing and selection here are all that the imagination could suggest. Pure fire reds, lemon yellows, orange, cream, and every possible combination; plants dwarf, tall, medium, some everblooming — new creations from a very ordinary plant. FLOWER POSSIBILITIES 219 In subsequent studies we shall see that there are methods of stimulating the production of new colors and color combinations through hy- bridization. But in this introductory chapter I am dealing chiefly with the simpler cases, and suggesting experiments that the amateur may undertake at the outset. The more complex cases will command his at- tention in due course. Meantime it should be stimulative to reflect that, by mere selection, demanding no knowl- edge of botany, no expert knowledge of horti- culture, but only the possession of reasonably acute vision and the exhibition of patience and persistence, it is possible to develop in the most commonplace flower garden blossoms whose color is at once unique and of enhanced beauty. Nor need attention be restricted to mere mat- ters of fragrance and color. I have already suggested that it is usually well to consider more than a single quality. Cases like that of the Heuchera leaf, in which for a special purpose a single quality alone is con- sidered, are exceptional. As a rule, you may advantageously bear in mind, at the same time that you are developing a new fragrance, the question also of color of flower and size and form. 220 LUTHER BURBANK At all events, so soon as your experiment has reached the stage at which you have a number of fragrant flowers from which to select, all of which have about the same excellence of per- fume, you will, as a matter of course, choose among these the one that combines with fra- grance the most desired qualities of color and form and size of blossom. DOUBLING THE PETALS AND INCREASING THE SIZE As to the matter of size, it is obvious that not much need be said. A glance shows which plant bears the largest flowers. And it may con- fidently be expected that the offspring of this plant will tend to produce flowers of exceptional size, and that some among these will exceed the parent plant in this regard. Precisely the same method of selecting, gen- eration after generation, with size of flower always in view, will lead to the production of a race of plants that tend to produce uniformly, under the right conditions of nourishment and care, flowers of a far larger size than those of the ancestral form. The matter of producing double flowers from a single variety — that is to say, flowers having two or more rows of petals instead of a single FLOWER POSSIBILITIES 221 row — may present greater difficulties. Not, in- deed, that any new principle is involved, but merely that a longer series of experiments may be required to produce the coveted double flower. The start must be made here just as in the other cases, by searching among the hundreds or thou- sands of plants for one that bears flowers hav- ing even a single extra petal. Seed of this plant being sown, it is likely that among the offspring there will be some that pro- duce not merely one extra petal, but possibly two or three. THE THREE REQUISITES Now you are on the road to success. Thence- forward it is only a matter of time, skill, and patience — the three essential requisites of plant development — combined with the dealing with large numbers of individuals. Exceptionally there may suddenly appear a seedling producing flowers that are fully double. In such a case, if the truth could be known, it would probably appear that some of the ances- tors of the seedling had produced — perhaps generations back — a double or partially double flower. Breeding from a double rose or carna- tion, almost all the seedlings revert to a single or semi-double form. 222 LUTHER BURBANK But in any event, once you have singled out a strain of flower that has the tendency to pro- duce extra petals, you will probably find this tendency accentuated, manifesting what I have elsewhere referred to as the momentum of vari- ation, and giving you results that are more and more encouraging each season. ASKING Too MUCH Should you attempt to produce a double flower coincidently with the attempt to improve the fragrance, color, and size of the same flower, you may presently discover that you are asking rather too much. The flowers that improve in odor and color and size may not be the ones that show the increased tendency to doubling of petals. In such a case, you may segregate the two groups, and carry forward the two lines of ex- periment coincidently in neighboring plots; and when you have attained a fair measure of suc- cess in giving one race of flowers perfume and color and size, and the other race a double or triple or quadruple row of petals, you may read- ily make a crossbreeding experiment through which you may combine all the desired qualities in a single hybrid offspring. FLOWER POSSIBILITIES 223 Even if the first-generation seedling of such a cross does not give you just the combination you are seeking, the second-generation offspring or a subsequent one are almost sure to reveal some plants that meet your expectations. So your simple experiments that began by mere selection will probably lead you to experi- ments in crossbreeding. THE Two BASIC ELEMENTS « Thus by natural stages you will have learned how to handle the essential tools of the plant developer. You will have learned that the two forces of heredity and environment are every- where operative, and must everywhere be your sole dependence. But you will have learned also that your wishes become an important part of the environment, when you determine which flowers shall be permitted to reproduce their kind; and that you also take a hand at deter- mining the line of action of hereditary tend- encies when you cross-pollinate the flowers, and decide which strains of heredity shall be blended. Let me in concluding this preliminary chapter name two or three common flowers with which the amateur may advantageously begin his work in selective breeding. 224 LUTHER BURBANK The rose and the carnation naturally suggest themselves, but they have been so much worked on that they do not leave so much opportunity for wide improvement as some less popular flowers, though offering grand opportunities for immediate but less unique results. The tulip is inviting, but calls for a good deal of patience. Perhaps the four-o'clock would serve the pur- pose as well as any other common flower. Also the hyacinth, the Scilla, and the gladiolus are peculiarly good flowers on which to work. There are many beautiful varieties of all of these but new sorts could readily be produced. Moreover, they are grown from bulbs, so any new varieties may easily be perpetuated — a consideration that is by no means without significance to the ama- teur who wishes to obtain striking results with the least expenditure of time. Details as to numerous other flowers, includ- ing both very common ones and those that are less usual, and varying from the simplest to the most complex, will come to our attention as we now take up in succession the records of my own work during the past forty-five years in the de- velopment of new races of flowers. WORKING WITH A UNIVERSAL FLOWER — THE ROSE HOW THE BURBANK AND OTHER ROSES WERE PRODUCED THE most popular of any roses I have so far introduced is undoubtedly the one known as the Burbank. The popularity of this rose is, I trust, well deserved. But I should not be disposed to admit that its merits are greater than those of many of my newer roses which have not yet made their appearance in public. The popularity of the Burbank is partly to be explained by the fact that it has been longer before the public. There is a time element in the introduction of a new flower, just as in the introduction of a new fruit. In fact, no new plant development could be expected to make its way except very gradu- ally at first, although if valuable it gains mo- mentum rapidly after a time. In this regard, the introduction of a flower is analogous to the 225 8 — Vol. 6 Bur. 226 LUTHER BURBANK development of the flower itself through succes- sive generations of variation. We have seen that when any given variation is in question, there is a tendency to much more rapid change after the experiment has pro- gressed a certain number of stages. Similarly a flower or fruit that the public at first accepts rather grudgingly may at last become so popular that it is impossible to pro- duce it rapidly enough to meet the demand. The Burbank rose, to be sure, did not fail of recognition from the outset. But its gaming of the gold medal as the best bedding rose at the St. Louis International Exposition in 1904 doubtless advertised it most extensively, and led to its rather exceptionally rapid acceptance by the public. On my own part, I look with particular pride on this rose, not so much because it received the gold medal as because competent judges every- where have admitted that it deserved the recog- nition thus given it as the best bedding rose then known. I have produced many plant developments that are much more spectacular than this new rose, and many that have elements of far greater novelty and interest from the standpoint of both plant developer and the general public. Yet I THE ROSE 227 may be permitted to indulge in a rather excep- tional satisfaction over the success of this flower for the reason that the rose is probably the most popular of all cultivated plants, and the one that has received most attention from horticulturists of all classes, professional and amateur alike. In attempting to introduce a new rose, then, the plant developer is coming in competition with a vast number of workers, and the product with which he operates is to be measured against an almost bewildering number of similar products that have attained a high degree of improve- ment. So, as I said, the plant developer may sometimes regard with greater satisfaction such an accomplishment as this, than a more spec- tacular achievement in plant development in a line where there is no competition. HOW THE BURBANK WAS PRODUCED The origin of the Burbank rose suggests in a way the origin of that very different plant de- velopment, the Burbank potato. I was not personally responsible for either name, and the analogy between the manner of production of the rose and the potato was doubt- less not at all in the mind of the dealer who christened the new flower. Still, as I have just intimated, there is a certain added propriety in THE BURBANK ROSE This picture reproduces a direct-color photograph from an oil painting. It represents the celebrated Burbank rose with the utmost fidelity. This is the rose that secured a gold medal at the St. Louis International Exposition in 1904, as the best bedding rose. This rose is a truly perpetual variety, bloom- ing constantly wherever climate will permit. The foliage is always and everywhere absolutely mildew, rust and disease proof. THE ROSE 229 the use of my name in connection with this par- ticular rose as against a good many other roses that I have developed, because of the fact that the manner of its production suggested that of the production of the first of my important plant developments. In a word, the Burbank rose, like the Burbank potato, owes its origin to the discovery of a seed pod on a plant that rarely produces seed. The plant in the present instance was a Bour- bon rose, of the familiar and typical variety known as Hermosa. This rose very rarely bears seed, even in California, but on one occasion I discovered half a dozen seed pods on a plant that did not differ otherwise in any obvious way from its companion plants. These seeds were carefully treasured, and from the plants that they grew are descended not only the Burbank rose, but also the Santa Rosa, and a number of others that are less well known. With the fact that the Burbank rose was a product of seeds thus accidentally garnered, however, the analogy with the Burbank potato ceases. For, whereas the tuberous vegetable was pro- duced in full perfection on one of the plants grown directly from the seeds found in the 230 LUTHER BURBANK potato ball, the Burbank rose was developed only after numerous hybridizing experiments in which new blood was introduced, and new qualities were brought into the combination. Among other roses, the strains of which were mingled with those of the offspring of the Her- mosa to produce the Burbank, was the Bon Silene. And there were at least three or four others that are similarly to be credited, although the exact pedigrees of all of them are not mat- ters of record. Still the initial impulse to variation which sup- plied the material for the new hybridizings, and was thus primarily responsible for the outcome, was given by the seeds gathered from the Her- mosa. The same tendency to increased vigor and productivity and variation that we saw manifested in the case of the potato, and to which reference has been made also in the case of the sugar cane, and of other plants that are usually propagated by division rather than by cross-fertilization, was doubtless given the seeds of the rose by a chance mingling of just the right kind of pollen — brought by some vagrant bee — with its usually unreceptive ovules. The lesson that cross-fertilization gives vigor, and provides the materials for variation, which we have seen emphasized so many times, is here THE ROSE 231 given a fresh illustration. It is a lesson that the grower of roses and other long-cultivated flowers may well bear in mind. When the resources of selection have been practically exhausted, and a particular variety of flower has reached a static period, in which it seems to present no further opportunity for development in a given direction — say as to its odor, or its color, or its size — the plant experi- menter should never forget that there still lies open to him the possibility of introducing new elements of variability, and new opportunities for improvement, through hybridization. This, of course, assumes that the flower has not been so specialized that all its stamens have been transformed into petals, so that it becomes absolutely sterile. Such a transformation has, indeed, been effected with a good many of the cultivated flowers, including some of the roses. And the case of Hermosa, just cited, illustrates the fact that some of our roses are practically sterile. Indeed most of them are so. But then the flower that has ceased to have productive stamens may sometimes still have a receptive pistil, so that new blood may be intro- duced from a species that retains normal virility —although in general, such flowers show small capacity even for accepting the pollen. A NEW YELLOW RAMBLER The ramblers, of many types, are favorites everywhere. Here is a yellow one that has obvious distinction. As yet it has no name. Profuse and beautiful in bud and bloom. THE ROSE 233 CHARACTERISTICS OF THE NEW ROSES The new Burbank rose and its sister plant, the Santa Rosa, present further object lessons in the value of cross-fertilization, in that they are not only much more beautiful than the original Hermosa from which they sprang, but that they also have qualities of hardiness and of produc- tivity that are the token of their mixed heritage. These new roses are, indeed, so hardy that they thrive in the northernmost parts of the United States and in southern Canada. They, are, perhaps, the hardiest of all everblooming roses. Their vigor and capacity for production of flowers are so great that they bloom incessantly throughout the season. Among all the roses there is none that excels them in the matter of almost perpetual blooming. The number of flowers produced by an individual plant is also quite out of the ordinary. Meantime the flowers themselves are very superior in color to those of the Hermosa, and the foliage of the plants is glossy and brilliant. These qualities were of course taken into con- sideration by the judges who gave the gold medal to the Burbank. But there were others which were given, no doubt, almost equal atten- 234 LUTHER BURBANK tion by the experts. One of these is the vigor- ous habit of growth of the plant, through which it comes about that it may be propagated almost as readily as a weed; will root almost as easily as blue grass, and will bloom when only two or three inches in height, and keep on blooming month after month, and year after year, if the buds are not actually frozen. Another exceptional quality, which some prac- tical horticulturists might regard as constituting a merit surpassing all the rest, is the power of resistance of the Burbank rose — which the Santa Rosa shares — to those ever-present foes of the rose family, mildew and rust. The new roses appear to be absolutely im- mune to the attacks not alone of these, but of other fungoid enemies. Their healthiness under all climatic conditions is their final and definitive quality. MAKING PLANTS IMMUNE TO DISEASE This quality of immunity to disease, while pri- marily due, no doubt, to the enhanced vitality given the plants through hybridization, has been accentuated and developed by persistent selection. In this regard roses do not differ from prac- tically all other plants with which I operate. I THE ROSE 235 have referred more than once to the method of developing immune races of plants, and empha- size it once more with propriety in the present connection, because, as is well known, the rose is peculiarly susceptible to the attacks of many fungoid and insect enemies. Indeed, many a rose that would otherwise have value is so susceptible to the attacks of dis- ease that it not only gives no pleasure to its owner, but becomes a source of infection in the garden that makes its presence a menace to other flowers. To give plants immunity to the chief dis- eases to which their species is subject is, there- fore, one of the prominent aims that I never overlook in the course of experiments, no matter what the particular quality that may be chiefly sought. Therefore it is made the invariable rule, what- soever the plant with which I am working, to examine the seedlings attentively from time to time, to note whether any of them give evidence of infection by mildew or any fungous growth. And any seedling that is seen to be subject to mildew is at once destroyed, regardless of the value of its other qualities. I should not regard a plant experiment suc- cessful that led to the production of the most ROSES AT SEBASTOPOL This picture gives a characteristic glimpse, in blossoming time, of some of the rose seedlings. Of the thousands tested, one or two may be saved, but not unless they are better than any rose now known. THE ROSE 237 beautiful and most fragrant and most prolific of roses, if at the same time the plant that exhibited these qualities was susceptible to mildew. In- deed, thousands of otherwise promising roses have been destroyed for the simple reason that they were subject to mildew. I have obtained scores of climbing roses that were worthy to compete with the Crimson Ram- bler or the Philadelphia Rambler and other standard varieties, yet which have not been allowed to live because of their susceptibility to disease. But the reward of this unflinching appli- cation of a principle has resulted in various types of roses that are quite generally mildew- proof. 'Among the ramblers just referred to, for example, by sedulous application of the prin- ciples of selection, preserving only those plants that showed themselves to have the quality of inherent resistance to the fungus, I have remain- ing, after thousands of their fellows have fallen by the wayside, a few rambler roses of wholly new types, which are immune to disease. This selection is not as difficult as might be supposed, because a rose that is intensely susceptible is gen- erally attacked during the first one or two years of its existence. 238 LUTHER BURBANK Moreover, these new mildew-proof ramblers manifest, partly perhaps as an evidence of the vitality that makes them immune to disease, a capacity to produce enormous clusters of the most beautiful flowers that approach the keep- ing qualities of some of the everlastings. Some of them will last at least a month, on the plant or when cut, showing thus a degree of per- manency hitherto quite unheard of among roses. ORIGIN or THE ROBUST RAMBLERS There are a great number of varieties repre- senting different crosses between the well- known Crimson Rambler and such roses as the Empress of India, Cherokee, Agrippina, Balti- more Belle, Banksia, Bon Silene, Papa Goun- tier, Cloth of Gold, Madame Edouard, Herriot, General Jacqueminot, La France, Lamarque, Marechal Niel, Cecille Bruner, Mrs. Robert Peary, Paul Neyron, Persian Yellow, Rainbow, Reine, Marie Henriette, Fortune's Yellow, WicJiuriana, and some hundreds of others. The cross of Empress of India with Crimson Rambler often have enormous stems, with deep- red hairy branches; while the hybrids of other crosses often have slender, smooth branches. But the hybrids themselves have been inter- bred, and other strains that seem to give good THE ROSE 239 promise were brought into their heredity, so that they have traits that do not belong to any of the original parents. Some of