No Two Living Things Exactly Alike
Infinite Ingenuity The Price of Variation
"Where do the flowers get their colors?" asked a visitor of Mr. Burbank one day. "From the bees, and the butterflies, and the birds," was the reply. "And from us."
Let us pick up a geranium, such as might be found in any dooryard in America, and see what Mr. Burbank meant. If we were to strip off its five brilliant petals soon after they have opened, and slice the base of the blossom in half, we should find ourselves looking into a tiny nest of geranium eggs-round, white, moist, mushy eggs with a soft skinny covering for shells. Carefully packed in a pulpy formation, these eggs, we should observe, are encased in a well protected nest, longer than its breadth, oval, except that its top extends upward in the form of a single tiny stalk. Surrounding this neatly packed nest of geranium eggs with its single upright stalk, and hugging it closely all around, we should see ten modified leaves, a quarter of an inch or so in length, ending, each, in a pointed stalk as big around, perhaps, as a bristle out of a hair brush; ten such leaves in two rows-as if shielding the egg chamber and its central stalk from harmful intruders. At the tops of the ten surrounding stalks, we should see the crosswise bundles, nicely balanced, of beautiful golden-orange pollen dust, loosely held in half-burst packages. And at their base, we should find the syrup factory of the geranium-a group of tiny glands which manufacture a sticky confection that covers the bottom of the flower with its sweetness. Shall we take one of the egg-like seeds from its nest and plant it? We might as well plant a toothpick. Shall we take a package of the pollen, and put it in the ground? We might as well sow a thimbleful of flour. But let us combine one of those eggs with a grain of that pollen, and three days in the soil will show us that we have produced a living, growing thing-a new geranium plant, with an individuality, a personality, of its own-an infant geranium, which we for the first time have brought into being-a thing which has never lived before, yet which has within it all of the tendencies inherited from ages of ancestry-tendencies good and tendencies bad, which wait only on environment to determine which shall predominate. By the simple combination of the pollen and the egg we have produced an entirely new plant, which may, if we will it, become the founder of a whole race of new and better geraniums.
How shall we go about it to make a combination, such as this, between the pollen dust and the seed-like egg so snugly stowed away within its nest? Let us examine that central stalk inside the double guard of pollen-bearing stamens and we shall have the answer. As the stamens fall away we begin to see a transformation in the stalk. Its upper end, which at first seemed single, now shows a tendency to divide into five curling tendrils-moist and sticky. Though we may plant pollen in the ground without result, we have but to place it on one of these sticky tendrils as they curl from the end of that central pistil stalk to start an immediate and rapid growth. Once planted there, the pollen grain begins to throw out a downward shoot, into and through the pistil stalk-forming itself into a tube which, extending and extending, finally taps the egg chamber and makes possible a union between the nucleus of that pollen grain and the egg below which awaits its coming. So, to produce a new geranium we have but to dust the grains of pollen upon the sticky stigma of that central pistil stalk; and when the flower has withered away, its duty done, we shall find within the egg chamber a package of fertile geranium seed ready for planting.
But there arises, now, a difficulty. While those little packages of pollen dust are there, the central pistil stalk inside keeps shut up tight, and it has no sticky surface on which to dust the pollen. And if we search for another blossom which shows an open, sticky pistil, we shall find that the pollen packages which once surrounded it have gone. To make our combination between the pollen grains and the egg-like seeds, therefore, we find it necessary to search first for one blossom which is in its pollen-bearing stage, and then for another blossom which has passed this point and shows a receptive sticky stigma-we are forced to make the combination between the two, instead of between the pollen grains and the eggs of a single blossom.
Which is exactly what the Mother Geranium intended we should do.
If the stigma of a blossom were at its receptive stage when the pollen packages around it burst open, there would probably be combined in the seeds of its egg chamber below, only the characteristics of one parent plant-only the tendencies of a single line of ancestry. The geraniums growing from those seeds would be so like in their tendencies of heredity that they would differ, individually, only as their individual environments differed. But when those eggs have brought to them the pollen from another plant, there are, confined within them, the tendencies and characteristics of two complex lines of ancestry; so that the plants into which they grow will be encouraged into variation and individuality, not as a result of environment alone, but as a result of the countless tendencies inherited from two separate lines of parentage. What a scheme for pitting the old tendencies of heredity against the new tendencies of environment-what an infinite possibility of combinations this opens up
Truly of a million geranium blossoms no two could be exactly alike-nor any two of their five million petals-nor any two of their ten million stamens-nor any two of their hundred million honey glands-nor any two of their billion pollen granules!
What we have seen in the geranium-those seed-like eggs, the sticky stigma and that microscopic pollen dust, we may see in some form or other in every plant that grows. The act which we might have performed to produce a new geranium plant-the combination of one of those seeds with some of that pollen-is going on about us always, everywhere-with the bees, and the butterflies, and the birds, and the winds, and a score of other agencies acting to effect those combinations. Which is the reason for the candy factory at the bottom of every geranium's little central well. And for those brilliant petals, and that delicate scent, and the picket arrangement of the stamen stalks, and the crosswise poise of their pollen-bearing anthers, and the central pistil stalk which rises upward from the egg nest-and everything that is beautiful and lovely in the bloom of that geranium-and the geranium itself.
Here is a plant, the geranium, so anxious to produce variations in its offspring that it has lost the power of fertilizing its own eggs and risked its whole posterity upon the cooperation of a neighboring plant. It has no power of locomotion-no ability to get about from place to place in search of pollen for its eggs or of eggs in need of its pollen; nor has its neighbor; so they call in an outside messenger of reproduction-the bee. The geranium makes its honey at the bottom of its blossom. It places movable packages of pollen dust balanced on springy stamens in such a way that, to reach the sweets, the pollen hedge must be broken through. It keeps its egg chamber closed and its pistil unreceptive while the pollen dust is there, and as if to advertise its hidden sweets to the nectar loving bees, it throws out shapely petals of brilliant hue and exudes a charming scent. And thus, the bees, attracted from afar, crowding into the tiny wells to get their sweets, become besmeared with pollen dust as they enter a pollen bearing bloom-and leave a load of pollen dust wherever they find a receptive stigma. Where did the geranium get its color? "From the bees," said Mr. Burbank. Just as the cactus covered itself with spines until it had built up an effective armor, in the same way the geranium, by easy stages, has worked out a color scheme to attract the bees upon which it depends to effect its reproduction.
In Mr. Burbank's yard there grows, as this is written, a Chinese arum whose color and whose scent reveal a different history. Unlike most common flowers which advertise to bees and birds and butterflies, this plant sends its message to the flies. Flies feed on carrion. The nectar of clover is not to their liking and the brilliant colors of our garden flowers fail to attract them. Our refuse is their food, and they are guided to it by colors and scents which are offensive to us. So this Chinese carrion lily, as it has been named-stranded at some time in its history, perhaps, in some place where flies were its only available messengers of reproduction, or blooming at a period when other means were not within its reach-has bedecked its spathe with a rich and mottled purple-in color and in texture resembling, from a distance, the color and texture of a decaying piece of liver. Just as the geranium supplements its advertisement in color with an advertisement in scent, so, too, the carrion lily has developed an individual odor-appeal, decidedly like that of meat too long exposed to the sun. So obnoxious and so penetrating is the odor of this flower that each year it has been found necessary to cut down the plant shortly after it has bloomed. And so truly has it achieved its ideal that even the buzzards, carrion birds that they are, attracted by its color, its texture and its smell, have descended in ever-narrowing circles-only to fly away in disgust when they found they had been lured by a flower.
Where the geranium finds it satisfactory merely to block the entrance to its honey store with an array of pollen bundles which must be pushed aside by the entering insect, the Chinese carrion lily makes doubly sure of pollination by means of a still more ingenious device. The fly, attracted by the color of the spathe and guided by the hidden odor at the base of the flower, lights on the sturdy spadix and uses it as a ladder for descent. The opening around the spadix is just large enough to afford a comfortable passage way; but once within the well, the spathe closes in and snugly hugs the spadix, so that the fly, buzzing about in, the chamber below, becomes thoroughly covered with the pollen dust. This done, the flower slowly unfolds and permits the pollen laden insect to escape.
Many other flowers show equal or greater ingenuity. In some varieties of the sage, the pollen-bearing stamens actually descend and quickly rub the yellow dust on either side of the insect, after which they fall back into their former position above the nectar cells. Most of the orchids, too, show an unusual ingenuity. One species bears its pollen in small bundles, the base of each bundle being a sticky disc. The structural arrangement of the flower is such that the insect cannot secure its nectar without carrying away at least one of the bundles. A pollen bundle glues itself to the head of the insect and curves upward like a horn. As soon as the insect has withdrawn from the flower, this pollen horn bends downward in front of the insect, close to its head, so that when the next flower is entered the dust can hardly fail to reach a receptive portion of the pistil. In this orchid there is but a single receptive stigma and the pollen bundles are separate and single, too; but in another orchid which has two receptive stigmas, the pollen bundles are in doublets, held together with a strap. Thus the insect visiting this second orchid carries away two pollen bundles on its forehead, each so nicely placed that their dust will reach both sticky stigmas of the next flower entered.
Similarly, the pollen of the milkweed is stored in two little bags, connected by a strap. When the bee visits the flower its feet become entangled in this strap and when it leaves it carries both bags with it. And so, throughout the whole range of plant life, each fresh investigation would show a new display of ingenuity-infinite ingenuity directed toward the single end of combining the tendencies of two lines of heredity-so that the offspring may be different from and better than the parent. We should see that there are those flowers which bloom only in the night. Flowers which, as if having tried to perfect a lure for the insects of the day, and having failed, have reversed the order of things and send forth blossoms of white or yellow-luminous colors always-to attract the moths that fly after the sun goes down.
We should find many interesting half hours of wonder contemplating such flowers as the honeysuckle, the nasturtium and many of the lilies-which have taken special precaution to place their nectar in long, horn-like tubes, out of the reach of insects, so that only the birds may become their messengers of reproduction. We should see the pathos of those flowers which advertise for insects that rarely come. The barberry, for example, which can be pollinated only during the bright hours of a cloudless day, and during a time so short that there is little chance of pollen being brought by insects from other blossoms. Each barberry blossom, ready for the insect if it should come, but as if expecting disappointment, makes sure of self perpetuation, if not of self improvement, by jabbing its pollen laden anthers on its own stigma with a motion as positive and as accurate as the jump of a cat. Or the fennel flower of France, in which the several pistils bend over and take pollen from the stamens around them and straighten up again. Or the flowers of the nettle, in which the stamens increase their height with a sudden spring-like action, showering the pollen up over the receptive stigma. We should observe that wheat and some of the other grains, as though discouraged by centuries and centuries of failure to secure variation, had settled down to the steady task of reproducing their kind exactly as it is, depending only on individual environment for individuality, and ensuring reproduction by self pollination. We should see plants in all stages of their attempts to keep their kind on the upward trend; we should see a range of ingenuity so great that no man, no matter how many of his days have been devoted to the study of plants and their ways, can ever become dulled to its wonders.
"I bought some extremely expensive seed corn several years back," complained a Santa Rosa farmer. "But, just as I expected, it ran down. The first year's corn was fine, and so was the second; but now it has gone clear back to ordinary corn. This plant improvement doesn't pay." "Do you know how corn reproduces itself?" asked Mr. Burbank. "Do you realize that if you plant good corn on one side of a fence, and inferior corn on the other, the corn cannot see the fence? Would you expect that a cross between a race horse and some family dobbin would produce a line of racers? Separate your good corn from your poor, and keep it by itself, and you will find that it does not run down, but even gradually improves. Every farmer knows that corn must be planted in large quantities close together-that a single kernel of corn, planted in one corner of a lot, apart from other growing corn, would be non-productive. Yet how many of those who depend upon corn for their living fully realize the reason for this? The geranium, with its nectar, its scent, its color and its structural arrangement, has built up a partnership with the bee to perform its pollination. While corn, with no advertisement, no honey, no brilliant reds, no scent, has developed an equally effective plan of making the breezes act as its messenger of reproduction."
Here is a plant, tall and supple, that responds with graceful movements to the slightest breath of air. At its top it holds a bunch of pollen laden tassels-swaying tassels which, with each backward and forward movement, discharge their tiny pollen grains in clouds, which slowly settle to the ground. Below, on the stalk of the plant, are the ears of corn, containing row after row of the egg kernels, needing but combination with pollen from above to become, each, a seed capable of starting another corn plant on its life. Just as the eggs of the geranium were housed in a protective covering, so, too, the corn eggs are sheathed in protective husks. And just as a tiny stalk protruded from the egg chamber of the geranium, so, too, does the silk which protrudes from the end of the husk serve the same purpose for the corn seed. Tear the husks from an ear of corn, and it will be seen that each strand of the protruding silk goes back to an individual kernel on the ear. That, between the rows of kernels, like electric wires in a conduit, each strand of the common bundle of silk protruding leads back to its separate starting place. To combine the characters of two parent corn plants, all that is necessary is to dust the pollen from the tassel of one on the silken ducts of the ear of another. And the breezes, as they swish a waving field of corn gracefully to and fro-as they play through a forest of pines, or as they ripple the grasses of our lawns-are performing their function in the scheme of reproduction as effectively as the bee does-when it goes from geranium to geranium in search of sweets.
Consider the simple salt-water cell, as seen reproducing itself under the microscope merely by splitting in two; and those two each becoming two, and so on endlessly. Observe that, with only a single line of parentage from which to draw tendencies, the individualities to be found in this, the lowest form of life we know, are molded wholly by the difference in the saltiness of the water, or the variation in its temperature, or those other limited changes within a short-lived environment. And then consider the geranium, and the Chinese arum, and the orchid, and the corn-with a thousand added complications in their lives brought about by a single dominant purpose-a thousand self-imposed difficulties and obstacles which would be needless except for that guiding desire to give the' offspring a better chance than the parent had! What a price to pay for variation! What ingenuity and effort each new combination of heredities has cost! How many must have been the plants which advertised for insects that did not come! How many, finding themselves in an unequal struggle, have perished in the attempt!
Truly, if the cost of things may be taken as a measure of their value, how much must this dearly bought variation be worth in the Scheme of Things! "The struggle of a plant to secure variation in its offspring does not end with the seed," said Mr. Burbank. "It only begins there."
In the tropics, a common tree near the seashore is the coconut palm. The coconuts which we find in our market, their hard shells outermost, are but the inside portion of the nuts as they grew on these trees. I When they were gathered, there was a fibrous substance surrounding the shell an inch or two in thickness-a woody fiber torn off by the shippers to cut down the cost of freight and cartage. Around this excelsior-like covering, as the nut grew on the tree, there was a skin-tight, waterproof cover, with a smooth or even shiny surface. At the top of the nut as it would stand if it floated in water, are three well defined eyes. Since these coconut palms grow, usually, along the water's edge, the nuts often roll into a brook, or a river, or the ocean, and float away. Once detached from the tree and started on such a journey, the eyes disclose their purpose. Two of them begin to throw out a system of roots, not on the outside of the coconut, but growing at first within the woody fiber between the shell and the outside skin. At the same time the other eye pushes out sail-like leaves extending several inches above the outer casing. Then, with sails set, and aided by the current of the stream, the nut starts out on its journey to find an environment of its own. Once landed, after weeks, perhaps, of travel, the roots which have been growing inside force their way out into the moist soil at the water's edge-the sail leaves begin to grow into stalks, which later develop into the trunk of the tree, the waves start to build new ground by washing sand around it, and the first page in the history of a new palm in a new environment is written.
The hard shell surrounding the stored-up milk in the coconut is there, obviously, as a protection from the monkeys; to prevent extermination through their liking for the milk. And that excelsior packing, and that waterproof housing, are these not as plainly the palm's attempt to provide for its baby tree a new environment?
We do not have to go to the tropics for evidences like these. There is probably no more familiar weed in our vacant lots than the common dandelion. Who can forget its feathery seed ball waiting, when ripe, for the first youngster, or the first draft of air to blow it away on its long sail through the air as it distributes its seeds-some on stones, perhaps, and some on plowed ground-such a multitude of seeds that, though many be lost, some will find themselves throwing roots into new soil, rearing their heads into new air-starting life in a new environment?
Or we might learn a lesson from one of the wild chicories which provides some of its seeds with wings to fly, while others it leaves wingless. Those seeds without wings fall at the feet of the parent plant as if to keep green the old family home; while those with wings fly away to start new families, under new conditions, where latent traits and tendencies-latent elements of weakness or strength-may cooperate to produce a better chicory. Or from that joy of childhood, the squirting cucumber, which, when ripe, fires its seeds, mixed up in its milky contents, with such force that they are sometimes carried a distance of twelve to fifteen feet. Or even the sweet pea, or our garden pea, which when their seeds have dried, have the ability to throw them some distance from the parent plant. In Mexico, there is the familiar jumping bean tree, which calls in an insect to aid in the distribution of its seeds. While these beans are still green, they are visited by a moth which lays her eggs in them. As they ripen, the grub hatches out and lives upon the food stored within. As if in partnership with the moth, the jumping bean tree has provided food for her offspring, so that the larva has plenty to eat without injuring the seed within the bean. And the grub, as it hollows out the bean and jumps about within it, causes it to turn and roll-rolls it into a new environment-repays its family debt to the tree which gave it food.
In the wooded mountains near Santa Rosa there grows a pine tree which has worked out an ingenious scheme for taking advantage of occasional forest fires to aid it in its reproduction. Most other trees mature their nuts or seeds and shed them every season. The animals may eat the fruit and carry the seeds afar, or take the nuts to new environments, or the seedlings may come up at the foot of the parent tree-but the process of seed bearing and seed shedding usually completes its cycle every fall. The pine tree referred to, however, does not shed its seeds in this way, nor is there any inducement in them or their covering to tempt an animal to carry them away. They grow in clusters about the trunk and branches, but remain attached to the tree. The cones which hold them do not even open. Sometimes nine or ten crops of these seed cones maybe observed clinging to a parent tree. But whenever the woods are visited by a forest fire, the cones are dried out by the heat, and the seeds, released, fall to the ground and sprout. In the localities in which these trees grow, there would be little chance for their seeds to germinate, in fact, except after a forest fire had cleared the ground. Against the competition of all of the hardy underbrush to be found in those localities, the mother tree, it would seem, fears that her seeds will have but a poor chance. Yet when the fires have cleared the ground and killed almost every other living thing, these seeds spring up almost as quickly and almost as thickly as grass on a lawn; and, competition removed, they grow with surprising rapidity into the making of a new forest. It has been observed that these trees grow usually along the sides of deep canyons where the destructiveness of the fire is the greatest-and only in canyons where forest fires are frequent-showing that without the aid of the fires, the tree cannot perpetuate itself. So firmly fixed has this partnership between the fires and this particular pine tree become that its seeds, if planted under other conditions, will not germinate. Taken from the tree, it is impossible to get them to grow even with the greatest care in good soil; but experiment has shown that, if placed for a few hours in boiling water, they will readily sprout even in poor soil. Thus, as if through a strange alliance, the forest fires clear the ground, scatter the cones and prepare the seed of this pine tree for germination; and the pine tree, in turn, rebuilds the forest which the fires destroyed.
The devil's claw, a tropical relative of our unicorn plant, has developed the power to bite and to hold on with almost bulldog grip, in its scheme of providing new environments for its young. This plant, growing low on the ground among other tropical vegetation where the distribution of seed becomes a problem, grows a seed pod of seven inches or more in length. Its seed pod, while maturing, is encased in a pulpy covering with a thick green skin, and its bulb and hook suggest some kind of gourd. When the seeds within are mature, the outside covering splits and peels away, disclosing a seed nest which is armored with spines more thickly than a prickly pear. That which, during its early stages, formed the hook, now spreads into two branches with pointed ends sharper than pins, almost as sharp as needles. Between these four-inch hooks, where they join the spiny bulb behind them, there appears a hole from which the seeds, if loosened from their former pulpy support, may, by pounding and thumping, find their way out into the world. As the seed pod lies on the ground, its sharp hooks coiled in exactly the right position, it awaits a passing animal. This spring trap may remain set for many months, but once an animal, big or small, steps between those fish-hook points, their mission is accomplished. The first slight kick or struggle to get away embeds them deeply, and at each succeeding struggle the hooks bite in, and in, and in, until finally the animal, in its efforts for release, pulls the seed pod from the plant and starts to run. Swinging to a leg or tail, suspended by the two sharp points of its prongs, the spiny housing of the seed pod comes now into play. At each bound or jump, the pod flops up and down, and its prickly points, adding to the pain of the ever-pinching hooks, are sure to keep the animal in motion. As the frightened beast makes haste to get away from an enemy which it cannot see, the seeds within the pod begin to loosen and fall out on the ground. When the last seed has left its shelter, the trap begins to fall apart-its object accomplished-its seeds scattered throughout a mile or more of new environment.
The sailor is awed by the mountains, and the mountaineer is awed by the sea. And we, too, are more apt to wonder at the jumping beans of Mexico and at the devil's claw of the equator than at the cherry tree in our own back yard-which outdoes both of these by forming a double partnership. Just as the geranium bids for the bees, so the cherry blossom, with its delicate pink and its store of honey advertises for butterflies and bees to bring the pollen from a neighboring tree. And this partnership concluded, the accounts balanced and the books closed, it then seeks new partners in the birds. That delicious meat around the seed, that shiny skin of red, and that odor of the cherry as it ripens-these are a part of the advertisement to the birds or animals-a lure to get them to eat the fruit and carry the seed as far as they may to another-a new-environment. Shall we wonder at the jumping bean and the devil's claw when our own cherry tree is getting the bees to give its offspring new heredities and the birds to surround these heredities with new environments in which to grow?
Wherever we look we see a new display of ingenuity-all for the sake of variation-variation which may mean retrogression as well as advancement-but such infinite variation that, surely, there can be found one out of a thousand, or one out of ten thousand, or one out of a million better than those that went before. Every flower that delights our eye, and every fruit which pleases our palate, and every plant which yields us a useful substance, is as delightful as it is, or as pleasing or as useful as it is, simply because of the improvement which has been made possible through variation.
-No two living things are exactly alike.
This text is from: Luther Burbank: his methods and discoveries and their practical application. Volume 1 Chapter 3