Popular Science Monthly/Volume 74/June 1909/Formative Influences
LELAND STANFORD JR. UNIVERSITY
WHEN I was a boy in New England it was the fashion to decorate the windows of the drug-stores with masses of huge deep blue crystals of copper sulphate—blue-vitrol or blue-stone. These ornaments have vanished now, even from the country drug-stores. Their places are taken by electrical toys, patent medicines, even animals. But these lumps of translucent crystals always interested me. Their composition is simple; sulphate of copper and water are their sole constituents. The sulphate of copper is itself a dull gray powder, not a crystalline substance at all; but if water is with it, it becomes blue, colors its solutions blue, and crystallizes in very regular form. The color and the form of these crystals depend, therefore, upon both water and copper sulphate.
The boy who plays with blue-stone, dissolving it in water and then recovering it again by crystallization, thus doing for fun what the freshman in a chemical laboratory does because he is directed, learns that the crystals will be large or small, few or many, according to the speed with which they form; large and few if they form slowly, small and numerous if they form rapidly. This is equally true of sugar, common salt and other crystalline substances. We see, then, that circumstances as well as substance have to be taken into account. Although we can not have crystals of this particular kind unless we have the sulphate of copper, neither can we have them, even with an abundance of the salt, unless we have water also. The water must not be in excess, lest the copper salt remain in solution; nor deficient, lest it remain amorphous. It must be exactly proportioned in quantity if the salt is to arrange itself into bodies of definite form. The size and the number of these bodies depend upon temperature, dryness of air, any circumstance, in fact, which influences the rate at which water evaporates from the solution.
Although the number, size and even the formation of blue-stone crystals depend upon circumstances, and will vary according to circumstances, circumstances can not make blue-stone crystals exactly like the crystals of other things. The crystals of common salt have characters which identify them to the eye and mind of the crystallographer. These characters, we say, are inherent in the substance itself. This may be true actually as it certainly is true practically; but a scientific man might be found who would hazard the opinion that common salt, which crystallizes in square plates with hollowed surfaces under the conditions which we know, might crystallize in another shape or remain amorphous on some other planet where the force of gravitation, the composition and pressure of the atmosphere, and other factors of its environment, would be different from those constituting our environment on this earth.
Students of the natural sciences reckon with circumstance as well as substance. Physicists and chemists know this, and work with a conscious realization of this fact. Of the biologists, none more keenly realize the significance of circumstance to the organism than physicians and surgeons. Sociologists dispute whether heredity or environment determines the qualities of the man. Many botanists and zoologists meantime are discussing fine-spun theories of heredity based on the infinitely more finely spun microscopic structure of plant and animal cells, devising a scientific vocabulary which breeds dictionaries while it veils our real ignorance of the facts concerned.
The thorough study of mankind, or of any other living or lifeless thing, involves a study of the substance of the thing and of its environment. Study of the simple substance of blue-stone and of common salt is comparatively easy; but the bodies of living things contain and probably consist of many substances, few of which are as simple as blue-stone and common salt. Definite chemical compounds, many of them complex and unknown, constitute the bodies of living things. These compounds possess their own properties, their own characteristics, inherent if you choose. Their behavior controls if it does not constitute the behavior of the living thing. But this behavior depends on circumstance, is controlled by environment. The living thing, human or vegetable, can not be known till its environment as well as its substance, and the influence of the one upon the other, are known.
The chaplain of this university, coming to my laboratory one day, was surprised by some machinery which he saw there and asked its purpose. I told him that I was proving that, if you took a slum-child early enough, you could make a decent man of him. My friend protested that I was omitting many links between the plants of my experiments and the less fortunate of the human race. While frankly admitting this, a scientific man may still believe that he can contribute to such proof by using guinea-pigs, or rats, or even plants, as the objects of his experiments. These experiments are designed to furnish information about the circumstances, the influences, the factors of the environment, which affect behavior.
We see the various factors composing our environment directing the movements of our fellows. A bright light or an unusual sound at once attracts notice, may even draw a crowd. The absence of light, generation after generation, has cost cave animals their organs of vision. Who can say that the perpetual noise of our cities will not induce changes in the nervous balance, if not in the organs, of men? The force of gravity, which enables a man to stand erect, defeats the unbalanced efforts of the baby learning to walk; it directs the growth of root and shoot from the sprouting seed; it forces organs and organisms to carry a very large proportion of their own weight or perish. When plants and animals live in water, over seven hundred and fifty times as much of their weight is carried for them as if they were growing in air. When plants are supported on trellises, or grow on trees, their mechanical strength, the development of their supporting tissues, corresponds to the lessened load. The buoyancy of the water and the mechanical support of trellise or tree, opposing the pull of gravity, modify and reduce its formative influence.
If we compare the great brown kelps growing along the rocky parts of the Pacific Coast, attached by hold-fasts to the bottom, floating upward and along the surface of the ocean till they become the longest plants known, with land plants, we find only some trees and such vines as the rattan at all approaching them in length. But in structure and in mechanical strength, what a difference there is! Bring the seaweed ashore and try to stand it up; take the vine down from its support; neither will be able to sustain its own weight. The force of gravity opposed, in the one case by water, in the other by the forest trees on which the rattan grows, has not exerted its full influence on either. The tree stands, and its trunk is composed of mechanically strong tissues, in part at least because of the pull of gravity only feebly opposed by the air.
Experiment proves the formative influence of gravity. The English gardener who trains his peach trees on the southern face of a wall knows well that such trees are mechanically weaker, though more prolific, than other peach trees growing unsupported in the same enclosure. The delicate stalks of the blossoms of apple, peach or prune, thicken and strengthen as the fruit sets, grows and ripens, the increased pull of gravity stimulating the living stalk to meet the greater strain by greater strength.
When we take into account the fact that the force of gravity acts constantly, that though we ordinarily ignore it or take it unthinkingly for granted (as we do the quality of our milk), it is an unchanging force, the same night and day, from season to season, from cycle to cycle, we begin to realize that it must exercise a formative influence of the utmost importance on all living things, stimulating the growing plant and animal to develop an adequate skeleton and to attain a balance of parts which will tend to stability.
Water opposes the force of gravity by buoying up, and carrying so large a fraction of the weight of, the creatures living in ponds, streams and the sea. In addition, it has a positive influence of its own. We are used to the directive influence which causes the wild creatures of field and forest to make the runways between den or nest and waterhole so charmingly described by Mrs. Austin. Every trout-fisherman has seen the roots of alder and willow growing from the bank into the stream. We are accustomed to having our house-sewers stopped up by the roots that will grow into them, though there is much more room outside. But the formative influence of water is not so obvious. Yet when we think of the creatures, plants and animals, of arid regions and of well-watered ones, we perceive certain differences. When we realize that water is formed, or is the surrounding medium, in almost every chemical reaction which takes place outside the living body, and in every chemical reaction within the living body, its importance is evident enough. The shape, size, structure and covering of every animal and plant are influenced by the ease with which water may be obtained and held. All land animals and plants lose water from their bodies by evaporation; submersed aquatics do not. Land animals and plants ordinarily get water from the earth, from depressions in its surface or from its soil, and only through those limited parts of their whole bodies which touch the water; but aquatics can take it in through their entire surface. If a land plant or animal takes in water only through its roots or its alimentary canal, there must be some system for distributing the water to all the parts of the body; but this is not necessary in aquatics. The differences in structure and form between land and water organisms is, then, partly due to their relations to water. The differences between the tadpole and the frog, between the submersed and floating leaves of the water-buttercup, between the swimming sperm of moss and fern and the wind-or insect-borne pollen of the higher plants, these differences are in their relations to water, in the degrees in which the formative influence of water has been unopposed by other factors.
Before turning to other formative influences, we should realize that the force of gravity acts constantly, night and day, uniformly, age after age, and it is impossible either to eliminate it in experiments or to conceive of its operation ever being or having been interrupted in nature. Water also is constant and uniform and unavoidable; for until water ceases to be a necessary component of the living protoplasm of the plant and animal body, until it becomes something else than hydrogen and oxygen in the proportion of two to one, we can not conceive of its being eliminated, by exclusion or substitution, in experiment, or of its absence in nature. If water is absent, life is absent. This is not true, however, of other influences, material or energetic, which affect form and substance, as well as the direction of growth or movement. These influences may be temporary.
Light is not a necessary condition of active life. It comes and goes, day and night. In the extreme northern mid-summer the sun never sets; the winter is dark and gloomy. In spite of the lack of light, however, life goes on in the winter darkness provided sufficient warmth is attainable. Nor is light uniform, for though the total seasonal light-fall may be, like the total seasonal rainfall, a moderately uniform quantity, yet we know that the light which reaches our eyes and plays on field and forest varies almost from moment to moment, as a wisp of cloud, a trail of smoke, or a bird or butterfly, passes between us and the sun. Yet with all this variation in quantity from day to night, and even from moment to moment, there is no variation in quality. The composition of sunlight, as it reaches the earth's atmosphere, is the same age after age; its red, yellow, blue and other rays fall upon animal and plant in similar proportions. Until the source of light changes, until the composition of the sun becomes altered by the exhaustion of this or that substance, the quality of light must continue the same.
The leaves, stems and flowers of our household plants turn toward the window. Plants growing under a hedge turn out to one side, if they are able to bear the shade long enough to get out of it. In the early morning, or toward sunset, one can often see the leaves of weeds all turned eastward or westward, according to the source of light. These are familiar instances of the directive influence of light, an influence which changes with the direction and the intensity of the light and is dependent upon some, not all, of the rays of ordinary daylight.
The formative influence of light is no less real and definite, although not so generally recognized. It determines whether a plant shall be stocky or straggling, short or long. Greenhouse men speak of spindly plants unduly shaded as "drawn." The ordinary broad, brown bean —Windsor, or Horse, or Spanish—sown in quantity in the vegetable gardens of those parts of the west where the paths of the padres lay— correspond in height quite as much with the light they receive as with richness of soil. If sowed too closely, each plant over-shading its neighbor, they grow in the same length of time to nearly double the height of others solitary. Young pines in too close stands are tall, slender, sparingly branched. The low stature of some of the plants of mountain-tops is due not merely to crushing snow, brief growing time, and chilly nights, but also to the greater brightness of the light which falls on them than on the floor of the valleys below.
Thus the vegetative parts are affected quantitatively by the quantity of light which reaches them. Stem and leaves reach their ordinary dimensions only under ordinary illumination. There are structural differences between the sunned and shaded leaves of wild plants. The beech offers the best known case.
Eastern greenhouse men spend anxious days before Easter lest their lilies bloom too late. They can control the temperature, moisture, soil, in their houses, but beyond certain narrow limits they can not control the light. The same plants bloom at a decidedly lower temperature in California than in the Mississippi Valley and on the North Atlantic slope. When the Weather Bureau can give as accurate measurements of the amounts of light reaching the soil in these different regions as of the temperatures, we shall see one reason for this difference. Even though flowers may be already formed, a certain though unknown amount of light is generally necessary to bring the flowers promptly to perfection. More than this, the number, size, color, fragrance and other qualities of the flowers, the number of eggs and sperm in them, even the formation of the flowers themselves, are dependent in very many plants upon an amount of light more than sufficient to maintain vigorous growth. This has been clearly shown by experiment on so many plants, simple and complex, as to lead one to think of light as a definite stimulus to reproduction. I can grow certain moss-like plants year after year in my laboratory and, according to their position, in a light or a dark place in the room, they will form reproductive organs or will remain sterile. I can do the same thing with submersed water-plants, and in garden and greenhouse the same fact is demonstrated year after year.
John Muir, in his "Mountains of California," gives the most glowing description of spring bloom which I know, where he tells of the San Joaquin Valley before it was settled. The newcomer to California to-day is struck with admiration of the great mats of color on hill-side and valley-floor. This prodigality of bloom far exceeds what one sees on either slope of the Alleghanies. Transplant the California "poppy" to any less sunny land and it degenerates; it blossoms less freely, its flowers are smaller, its petals are more sulphur or lemon than orange-yellow, its seeds are smaller and fewer. It seldom grows, still less blooms, under the shade of the live-oaks, though the open field may be golden with them. The more shade, the less bloom.
Testing this conclusion by experiment on plants very different in shape and size in their vegetative and reproductive stages, as is the case in Sempervirens and similar squat plants used for bedding or bordering, it has been found that the reproductive stage may be indefinitely postponed by growing the plant in feeble diffused light. Rather more light stimulates the plant to send up a stalk from its rosette of leaves, but this stalk is leafy. Still more light will induce the formation of flowers; but only when fully illuminated will the plant form perfect flowers and set good seed.
Cultivated violets are from eastern and European stock. In the middle west, in New England and in northern Europe, violets of many species form, in addition to the conspicuous blue flowers, others ordinarily concealed by the leaves. These hidden flowers are white or pale, lumpy, and closed. In certain districts in Italy, the same species of violet do not form these closed (cleistogamous) flowers. In the sunniest parts of California gardens the violets never form them. Other plants form cleistogamous flowers, but the number of these species in different regions is very clearly related to the amount of sunlight. Northern Europe, New England and the northeastern part of the Mississippi Valley have less sunshine than the great western plateau, the Rocky Mountain region, Italy and California. There are some species of cleistogamous plants on the plateau and in the Rocky Mountain region; there are more on the two slopes of the Alleghanies and in Europe. Only a species or two have been found in central California, and these live in the dim light of virgin redwood forest.
Animal physiologists have not yet shown, I believe, that the breeding-seasons of animals generally mark the reaction of these animals to external influences. There is obviously every reason why birds should not mate till the rigors of a severe winter are over. The breeding-season of frogs and toads must coincide with the season of abundant water in ponds and pools. But I am inclined to believe that where there are no seasonal differences, or only very slight ones, in light, warmth, rainfall, there are only slight differences in the habits of plants and animals. Sea-urchins, for example, like many of the sea-weeds, have no regular breeding-seasons; the changes are slight in the water which nearly always covers them. On the other hand, land animals, subject to the more pronounced changes in their habitat, have their cycles of vital processes to correspond.
Light stimulates flowers to form; it stimulates the violet to develop one kind or another according to the amount of light. Light influences the growth of leaves and stems by its direction quite as much as by its amount. The direction from which light comes determines also where and how a plant part shall form. Vertical leaves, like those of onion and eucalyptus, are alike both structurally and superficially on the two sides. Horizontal or oblique leaves evidently differ on their two faces. Light has much to do with this difference. The reproductive stage of the fern is a small, flat, leaf-like plant, usually growing closely applied to the soil, its upper side lighted, its under side dark. If, for purposes of experiment, the light is made to come from below or from one side, instead of from above, the reproductive organs form, as before, on the side away from the light. They always form on the dark side, whether this is above or below, or more or less vertical. Light and not gravity is here the formative influence, stimulating the reproductive organs to develop and determining by its direction the side of the plant which shall bear them. Sometimes there may be a conflict of influences. If there is no dark side, because the plant is equally illuminated on both sides, the reproductive organs will form equally on the two sides.
If the direction of illumination determines where the reproductive organs of these small fern-plants form, may it not also influence the shape of the plants themselves? It may. There are many small leaf-like plants, allied to the mosses and ferns, growing against soil, or bark, or rock. Their structure is dorsi-ventral. When these little plants first start, they are erect and cylindrical; the divisions of the fertilized egg-cell from which they spring are at right angles to the source of light. Presently, however, these little cylinders tip over and, the light still coming from above, they spread out at right angles to it. Thus the erect cylindrical form and radial structure soon give place to prostrate leafy form and dorsi-ventral structure. It is now known in at least one case, and suspected in many others, that if the little plants can continue to receive light symmetrically, their form will be correspondingly symmetrical. By slowly revolving them for months after sowing, so that they were equally illuminated on all sides in succession, I have obtained plants which were as cylindrical at the end of my experiment as in the early weeks. Where the illumination was equal, the structure was perfectly radial; where it was unequal, the structure was dorsi-ventral.
This matter of bodily form, different or like in two succeeding generations, depends upon the direction from which the light comes. If the offspring have a one-sided illumination, as their parents did, their form will be flat and-prostrate like their parents; but if the offspring are symmetrically lighted, they will be symmetrically formed in spite of the difference from their parents.
So far as these experiments contribute at all to the solution of biological or sociological problems they do so by indicating that like influences produce like effects on the same substance, and that, although the substance may be the same, unlike influences will produce unlike results. They make us a little more confident that the child of vicious parents, if itself sound, can be made into a much more desirable citizen if brought under influences different and better than those surrounding and exerted by its parents.
The formative influences so far discussed produce normal and healthy effects. The deformative and pathogenic influences which affect human and other animal bodies have their parallels among plants. Besides the plainly marked plant-diseases due to such obvious parasites as borers, rusts, rots and mildews, there are influences no less real, although easily overlooked.
City life is unfavorable to plants. Atmospheric and soil conditions are either bad or not bad, they are never good. One need only pass along a street in which the gas-pipes have been exposed to know that the soil is more or less saturated with stale illuminating gas. The odor is offensive. Trees rooted in soil poisoned by large or small, but always continuous doses, of illuminating gas, do not thrive. Their leaves are never the full rich green of trees in the country, the foliage yellows early and many leaves fall. Add leaky electric wires, leaky sewers, and the putrefactions going on in fouled soil, and one realizes the cause of the chronic lack of vigor of street shade trees.
The trees in yards, gardens and parks are only somewhat better, they are not entirely well. An atmosphere polluted by the products of all our fuels except wood contains active poisons, not merely inconveniences. Because there is less soot in New York and San Francisco the inhabitants speak boastingly to their less fortunate friends in Chicago or St. Louis. But the smoke problem of cities is a problem of gaseous, not solid, emanations. Smoke-consumers, so-called, add to the bearableness of urban existence by reducing one disagreeable feature. They do not in any way affect the more serious ones. The sulphurous and chlorine gases, even sometimes fluorine, escaping from the chimney-tops of the office and factory buildings, and from the dwelling houses, of a city of diversified activities, affect human, animal and plant life. Certain wild plants which one would expect to see on the tree-trunks and stone walls in towns where the air is humid, are entirely absent. They have disappeared, in fact, from European cities since the use of coal became general.
If one would have a clearer view of what the effect of these gases is let him go where they are discharged in greater proportions into the air and note the effect on the native vegetation. Wherever smelters are in operation, treating sulphurous ores of copper, zinc, mercury, plants sooner or later disappear. Forest and farm suffer and finally become almost or quite valueless. This is simple poisoning, resulting, where the dose is great, in death.
The egg of a gall-fly laid in or in contact with developing tissues, hatching a grub which feeds and grows and excretes, becomes surrounded by a growth unlike anything else which the leaf or branch would develop, a growth of plant-tissue characteristic of the particular kind of plant and of the particular kind of fly. This developing tumor is the result of the presence of the grub, of the formative influence of this parasite. Similarly, the tubercles developing on the roots of many plants exhibit the formative influence of the worms or of the bacteria without which they would not start, much less develop, as they do.
The life-experiences of all living things, and even the things themselves, are the joint product of substance and circumstance. Some, if not all, of the substance is continuous, transmitted, from parent to offspring; some, but not all, of the circumstance attending this from the beginning to the end of its existence, is continuous. In the continuity of substance and circumstance lies the basis of the likeness of succeeding generations: in the difference of circumstance from time to time lies the basis of the difference which we see between offspring and parents. For circumstance is but Emerson's synonym for the evolutionist's word environment; and environment, on analysis, proves to be the sum of the formative influences.