HOW THE CACTUS GOT ITS SPINES-AND HOW IT LOST THEM
A SIDELIGHT ON THE IMPORTANCE OF ENVIRONMENT
It is the acre-and-a-quarter patch of spineless cactus on Luther Burbank's experiment farm which first strikes the visitor's eye. In the same yard there are 2500 other experiments under way-new flowers, fruits, vegetables, trees and plants of all descriptions such as man has never before seen, but the velvet slabbed cactus-freed from its thorns-seems more than a plant transformation, it seems a miracle. Since the spineless cactus represents the typical Burbank boldness of conception, and reflects the typical Burbank skillful execution, we may as well begin with it. It occurred to Luther Burbank one day that every plant growing on the desert was either bitter, or poisonous, or spiny. It was this simple observation which gave him the idea of this new plant-a plant which already has shown its ability to outdo alfalfa five to one, and which promises to support our cattle on what have been the waste places of the world; so that our ranges may be turned into gardens to produce the vegetable sustenance for multiplying population. Let us look at the life story of the cactus as it unfolded itself to Luther Burbank when he realized the importance of the simple fact that desert plants are usually bitter, poisonous, or spiny. "Here are plants," thought he, "which have the hardiness to live, and to thrive, and to perpetuate themselves, under conditions in which other plants would die in a day or a month. "Here are plants which, although there may be not a drop of rain for a year, two years, or even ten, still contrive to get enough moisture out of the deep soil and out of the air, to build up a structure which, by weight, is ninety-two percent water-plants which contrive to absorb from the scorching desert, and to protect from the withering sun, enough moisture to make them nearly as juicy as watermelons. "Here are plants which are veritable wells of water, growing in a. land where' there are no springs, or brooks-nor even clouds to encourage the hope of a cooling rain; here are plants which [v1-1-2 pg 9] are rich in nutriment for man and for beast, here in the desert where the demand for food is the most acute-and the supply of it the most scanty. "And here they are, ruined for every useful purpose, by the bitterness which makes them inedible, or the poison which sickens or kills, or the spiny armor which places their store of nutriment and moisture beyond reach. "There must be some reason for that bitterness, that poison, those spines. "What other reason could there be than that these are Nature's provisions for self defense? "Here are the sagebrush, with a bitterness as irritant, almost, as the sting of a bee, the euphorbia as poisonous as a snake, the cactus as well armored as a porcupine-and for the same reason that bees have stings, that snakes have fangs, that porcupines have arrow-like spines-for self protection from some stronger enemy which seeks to destroy."
Self preservation comes before self sacrifice, apparently, in plant life just as it does in human life. The plum trees in our orchards outdo each other in bearing fruit to please us; the geraniums in our doorvards compete to see which may give us the greatest delight. But may it not be because, for generations, we have fostered them, and nurtured them, and cared for them? May it not be because we have made it easy for them to live and to thrive? May it not be because we have relieved them of the responsibility of defense and reproduction, that they have rewarded our kindly care by fruiting and blooming, not for their own selfish ends, but for us? No man was ever kind to a cactus; no man ever cultivated the sagebrush; no man ever cherished the poisonous euphorbia. Is it, then, to be wondered at that the primal instinct of self preservation has prevailed-that what might have been a food plant equal to the plum transformed itself into a wild porcupine among plants? That what might have been as useful to the horse as hay changed its nature and became bitter, woody, inedible? That what might have been a welcome friend to the weary desert traveler grew up, instead, into a poisonous enemy?
"If the bitterness, the poison and the spines are means of self defense," thought Mr. Burbank, "then they must be means which have been acquired. The plants were here before there were animals to feed on or destroy them, so there must have been a time in their history when they had no need for such defense. "It must be true, then, that away back in their ancestry there were desert sagebrushes which were not bitter, desert euphorbias which were not poisonous, and desert cactus plants which had not even the suspicion of a spine. It could only be the long continued danger of destruction which could have produced so radical a means of defense. "We have, then, but to take these plants back to a period in their history before defense had become a problem-in order to produce an edible sagebrush, a non-poisonous euphorbia, a spineless cactus." How, in a dozen years, Mr. Burbank carried the cactus back ages in its ancestry, how he proved beyond question by planting a thousand cactus seeds that the spiny cactus descended from a smooth slabbed line of forefathers-how he brought forth a new race without the suspicion of a spine, and with a velvet skin, and how he so re-established these old characteristics that the result was fixed and permanent - all of these things will be explained in due course where the discoveries involved and the working methods [v1-1-3 pg 13] employed may be made applicable, as well, to the improvement of other plants. It suffices, here, to say that, beginning with his simple observation and reading the history of the cactus from its present-day appearance, he was able to see outlined before him the method by which a plant yielding rich food and forage has been produced, which, more than any other plant, promises to solve the present-day problem of higher living costs.
"But, Mr. Burbank," asked a visitor at the Santa Rosa Experiment Farm, "do you mean that the cactus foresaw the coming of an enemy which was to destroy it? Is it believable that a plant, like a nation expecting war, could armor itself in advance of the necessity? And if the cactus did not know that an enemy was later to destroy it, would it not have been destroyed by the enemy before it had the opportunity of preparing a means of defense?" Let us look into the history of the plant as it revealed itself to Mr. Burbank and see the answer to these questions.
The likelihood is that parts of Nevada, Arizona, Utah and Northern Mexico were once a great inland sea-that the deserts now there were the bed of that sea before it began its long process of leakage or evaporation. In these regions, so far as is known, the North American cactus seems to have originated. Back in the ages before the evaporation of the inland sea was complete, the heat and the moisture and the chemical constituents of the sandy soil combined to give many plants an opportunity to thrive. Among these was the cactus, which was an entirely different plant in appearance from the cactus of today, no doubt, with well defined stalks and a multitude of leaves, each as broad as a man's head. As the heat, which had lifted away the inland sea, began to parch its bottom, the cactus, with the same tendency that is shown by every other plant and every other living thing, began to adapt itself to the changing conditions. It gradually dropped its leaves in order to prevent too rapid transpiration of the precious life-supporting moisture. It sent its roots deeper and deeper into the damp sub-stratum which the sun had not yet reached. It thickened its stalks into broad slabs. It lowered its main source of life and sustenance far beneath the surface of the ground and found it possible, thus, to persist and to prosper. Perhaps there were, in the making of the [v1-1-4 pg 16] desert, other plants not so adaptable as the cactus, plants which perished and of which man has no knowledge or record. And so, we may assume, the cactus and those other plants which adapted themselves to the new conditions crowded out those which were unable to fit themselves to survive, and covered the drying plains with their verdure. But there came animals to the bed of this one-time sea, attracted, perhaps, by the cactus and its contemporaries, which offered them food of satisfying flavor and easy access. Of the plants which had survived the evaporation of the sea and the heat of the broiling sun, there were many, quite likely, which failed to survive the new danger-the onslaught of the animals. Species by species the vegetation of the desert was thinned out by the elements and by the animals; and the animals, with plant life to feed on, multiplied themselves in ever increasing hordes, till perhaps the cactus was but one of a dozen plants to survive. Then came the fight of the cactus to outdo the beasts which sought to devour it-the fight as a family, and the fight within the family to see which of its individuals should be found fit to persist. Of a million cactus plants eaten to the ground by ravenously hungry antelopes, we will say-antelopes which had increased in numbers year by year while their food supply year by year was relentlessly dwindling - of these million plants gnawed down to the roots, perhaps but a thousand or two had the stamina to throw out new leaves-and to try over again. But just as in its previous experience, the cactus had changed the character of its stalk, so now it undertook another change-the acquisition of an armor. This armor at first consisted of nothing but a soft protuberance, a modified fruit bud or leaf, perhaps, ineffectual in warding off the onslaughts of the hungry animals. So, of the thousand or two left out of the million, there may have been but a hundred which were able to ward off destruction. The hundred, stronger than the rest, though eaten to the ground, were able still to send up new leaves, and with each new crop the hairs became stiffer and longer, the protuberances harder and more pointed, until finally, if there were even only one surviving representative of the race, there was developed a cactus which was effectually armored against its every animal enemy. One such surviving cactus, as transformed throughout ages and ages of time, meeting new [v1-1-5 pg 19] conditions with changes so slight as to be almost imperceptible, but gradually accommodating itself to the conditions under which it lived and grew-one such survivor out of all the billions of cactus plants that have ever grown, would have been sufficient to have covered the deserts of the world with its progeny-to have produced all of the thorny cactus which we have in the world today.
"You see," said Mr. Burbank, "the cactus did not prepare in advance to meet an enemy-it simply adapted itself to changing conditions as those conditions arose. First, surviving the desert drought and the broiling sun, it threw its roots deep so that its main. source of life was below ground. Then, attacked by an enemy which ate off the leaves above the surface, it still had life and resistance to try again. Ineffectually, at first, it began to build its armor, but each discouragement proved but the incentive to another attempt. It is a vivid picture: the whole cactus family in a death struggle for supremacy over an enemy which threatens its very life - millions and millions of the family perishing in the struggle, and perhaps but one victorious survivor left to start a new and armored race. "It is wonderful, too; but, whenever we plant a cactus slab today we see evidences of adaptability more wonderful than this. "The slab of cactus is a brilliant green as we put it in the ground. It is flat, of an oval shape, an inch or less in thickness. Its internal structure is of soft, mushy fiber, mostly water. "As that slab sends down roots, it begins to prepare itself to bear the burden of the other slabs which are to grow above it. "The thin, flat shape thickens out until it is almost spherical; thus presenting a curved surface in four directions instead of in two, it braces itself against the winds which will play with the new slabs far above it. "Its mushy wood fibers grow tough and resistant; it loses much of its watery character. "It changes in color, from green to brown; it loses its velvety skin and develops a bark like that of a tree. "Within a year after planting, this cactus slab will have changed in appearance and in characteristics to fit itself to the new conditions which surround it. "It will have changed its structure to bear weight and stand strains. It will have modified its internal mechanism to transmit moisture instead of to store it. It will have remodeled its outer skin to protect itself from the ground animals from [v1-1-6 pg 22] which, when it was a slab high up on another cactus plant, it knew and feared no danger!"
Is it more wonderful that, unseen by us, a plant should have adapted itself to the desert and, through the ages, have armored itself against an enemy, than that, before our eyes, in a single year, it should meet changed conditions in an equally effective way? Is it more wonderful that it should grow spines than that it should grow slabs which in turn have the power to grow other slabs? Is not the really wonderful thing the fact that it grows at all?
The cactus is one of the most plastic of plants-educated up to this, perhaps, by the hardships and battles through which its ancestry has fought its way. A slip cut from a rose bush, for example, must be planted in carefully prepared ground of a suitable kind, at a certain time of the year, with regard to moisture and temperature-it must be watched and cared for until it takes root and begins for itself. Under continued cultivation, the rose bush has lost some of its ability to make its own way. But the cactus, having come up from a line of warriors with every hand against it, needs no such care. Every one of the fifty or more wart-like eyes on its every slab is competent to throw out a root, a fruit, or another slab-whichever the occasion seems to warrant. Lay a cactus slab on hard ground, unscratched by a hoe, and the eyes of its under side will throw long yellow roots downward, while the eyes on the upper side await their opportunity, once the slab is rooted, to throw their other slabs and their blossoms upward. As the tiny buds grow from the eyes, it is impossible by sight or microscopic examination to determine which will be roots, which will be fruits, or which will be other slabs. It is as though the cactus, inured by hardship and prepared for any emergency, waits until the very last possible moment to settle upon the best-suited means of reproduction-as though the bud, having started, becomes a root if it finds encouragement for roots, or a fruit if seed seems desirable, or an upward slab if this can be supported. Nor does its attempt at reproduction require much encouragement. Fifty young cactus slabs laid on a burlap-covered wooden shelf four feet above ground were found to have thrown long roots down through the burlap and through the cracks of the boards within a few days. [v-1-1-7 pg 25] A cactus plant pulled from the ground and tied by a string to the branch of a tree remained hanging in the air for six years and eight months. During this time it had no source of nourishment, and its slabs withered and turned brown. But, planted again by sticking one of its slabs six inches in the ground, it immediately took root, and within a few weeks began to throw out new blossoms and slabs. Another detached cactus slab, long forgotten in a closet, and after having been in the dark for more than a year, was found to have thrown out a sickly looking baby slab when the closet door was left open for a few days. The more the adaptability of the present-day cactus and its tenacious hold on life are observed, the easier it becomes to understand its fight against a devouring enemy which lived during the desert-forming age, and to see the origin of the thorny cactus of today.
Nor is the cactus the only desert plant which shows evidences of such a struggle. The goldenrods of the desert are more bitter than the goldenrods of the plains. The wormwood of the desert is more bitter even than the wormwood which grows where there have been fewer enemies. [v1-1-8 pg 27] The yuccas, the aloes, the euphorbias, all have counterparts in their families which, needing less protection, show less bitterness, less poison, fewer spines. And even rare cactus plants from protected localities, and those of the less edible varieties, give evidence, by the fewness of their spines, that their family struggle has been less intense than the struggle of the cactus which found itself stranded in the bed of a former inland sea.
Plants which have shown even greater adaptive powers than the cactus are to be found in the well known algae family. One branch of this family furnishes an apt illustration of the scant nourishment to which a plant may adapt itself. Microscopic in size, it lives its life on the upper crust of the Arctic snow storing up enough energy in the summer, when the sun's rays liquefy a thin film of water on the icy surface, to sustain life in a dormant stage during the northern winter's six months of night. With nothing but the moisture yielded from the snow, and what nutriment it can gather from the air, this plant, called the red snow plant, multiplies and prospers to the extent that it covers whole hillsides of snow like a blanket-covers them so completely that the reddish color of the plant, imparted to the snow, first gave rise to the tales of far northern travelers as to the color of the snowfall and explained the apparent phenomenon of red snow. Another division of this family, going to the opposite extreme, thrives in the waters of Arrowhead Sulphur Springs in California-lives its life and reproduces itself in water so hot that eggs may be easily cooked in it. Contrasted with these microscopic members, one thriving on the Arctic snows, the other in water at the boiling point, there is still another member of this family which has become the largest plant in the world. This, the gigantic seaweed of the Sargasso Sea, is taller and larger than the greatest giant redwood which California has produced. And so on; some of this family of the algae grow on and in animals, some on other plants, some on iron, some on dry rocks, some in fresh water, and some in the salt seas.
The monkey-puzzle tree, a form of which is illustrated by a direct color photograph print, shows an adaptability to environment as striking as that of the cactus-although for an entirely different purpose. At the top of the monkey-puzzle tree, so called, [v1-1-9 pg 30] are borne several nuts containing the seed of the plant. In the case of the cactus the thorns were thrown out to protect the plant itself from destruction, but in the case of the monkey-puzzle tree the animals threatened not the tree itself but its offspring-its nuts were so highly prized by the monkeys, and their number was so few, that it was forced to take protective measures to keep its seed out of the reach of enemies. From this we begin to see that each plant has its own family individuality, its own family personality. Some plants, in order to insure reproduction, produce hundreds or thousands of seeds, relying on the fact that in an over-supply a few will likely be saved and germinated; while other plants producing only a few seeds protect them with hard shells or bitter coverings, or, as in the case of the monkey-puzzle tree, with sharp spines which make access impossible.
In the deep canyons of California's mountains there grows a member of the lily family, the trillium. At the bottom of these canyons there are places where the sunshine strikes but one side. The flowers on the shady side of the canyons are larger, and the leaves of the plants are broader, and the bulbs are nearer the surface than those of the plants which grow where the sun gets at them. On the other side of the same canyons the bulbs grow deep in the soil, and the leaves and the blossoms transform themselves to protect their moisture from the sun. Which is all that the cactus did when the sea was turned into a desert.
Along the Pacific coast from Oregon well down into California, there grows a common wild flower of the pipewort family. Inland a little way, say ten or fifteen miles, the stalk of this plant is smooth and with hardly the suspicion of a hair. But along the shore, where the northwest winds pick up all of the finer particles from the beach and form a sand blast, the plant has developed a stalk so covered with hairs that it is as woolly, almost, as a sheep-perfectly protected against the sand-enemy. Which is all that the cactus did when the antelopes came to destroy it.
Let the cactus, battle-scarred and inured to hardship, teach us our first great lesson in plant improvement: That our plants are what they are because of environment; that simply by observing their [v1-1-10 pg 33] structures, their tendencies, their habits, their individual peculiarities, we can read their histories back ages and ages before there were men and animals-read it, almost, as an open book; that our plants have lived their lives not by quiet rote and rule, but in a turmoil of emergency; and, just as they have always changed with their surroundings, so now, day by day, they continue to change to fit themselves to new environments; and that we, to bring forth new characteristics in them, to transform them to meet our ideals, have but to surround them with new environments-not at haphazard, but along the lines of our definite desires.
-Is not the really wonderful thing the fact that the plants grow at all?
{END OF CHAPTER 1}