Personality of plants

by Royal Dixon; Franklyn Everett Fitch

The Acacia is a plant which closes up at night; the same phenomenon is very striking in the Oxalis. The common Bean sleeps standing: that is, its leaves close upward instead of downward. The little blue Veronica flower, so strikingly brilliant and attractive in the daytime, tucks itself in so snugly at bedtime that it becomes quite inconspicuous. A Marigold called Calendula Pluvialis even contracts its corolla every time the sun is veiled by a passing cloud. These sleep movements all have a scientific purpose. Their main object, just as in animals, is to reduce bodily activities to a low ebb and so to give the plant a chance to recuperate for another day’s efforts. The contraction of all surfaces cuts down the radiation of heat and moisture and presents less resistance to outside elements. The plant is in a quiescent, somnolent state.

There are other movements of leaves and flowers the object of which is not quite so apparent. For instance, there is the Hedysarum Gyrans or Oscillating Sainfoin. Each of its leaves has three folioles. The center one is very large and stands bolt upright, except at night, when it condescends to bend its head in sleep. The two lateral folioles are in perpetual oscillation both day and night. Nothing but a very hot sun seems able to stop their movement. Possibly, this plant is a fresh air fiend which requires a steady atmospheric flow upon its respiratory surfaces! The two lateral folioles of each leaf are delegated to act as fans and blow a constant supply of air upon their majestic brother.

Similar oscillations have been noticed in some Orchids, where a part of the flower’s corolla rises and falls with a regular rhythm not unlike the beating of a human pulse.

The stamens and pistils of flowers sometimes have the power of movement. If an insect, wandering about in the flower of the Barberry Tree (Berberis Vulgaris), happens to touch the base of a stamen, it bends forward with a quick, spring-like motion and presently straightens up again. The evident intent is to shower some pollen on the little intruder with the hope that he may carry its vital principle to some neighbour of the same species.

In the Parnassia Palustris, fortunate observers have sometimes seen the five stamens bend forward and beat on the head of the pistil in rotation as if on an anvil. Perhaps outside pollen-carrying agencies have passed this particular flower by and, in desperation, it is resorting to self-fertilization.

The Junger Mania, a plant allied to the Mosses, shows knowledge of the laws of mechanics when it uses a natural spring coiled in a small tube to project its seeds out into the world. Seeds of fresh-water Algae swim about for a few hours after leaving their mother-plant, vibrating their cilia with great rapidity. It is the ability of certain one-celled plants to move about freely which causes considerable discussion as to whether they are really not animals. The Diatoms are examples. They propel themselves through the water by oscillating their whole bodies from side to side. To reverse their direction they go backward like a ferryboat.

The ancients as far back as Aristotle recognized the sensitiveness of plants to light and their eager use of its life-giving properties. In fact, one has only to watch the Sun-Flower follow the orb of day across the heavens to realize that there must be something vital in sunlight for the plants. What interests us is that they have the instinct or the knowledge to so present their surfaces to the light that they receive a maximum benefit from its influences. From the aristocratic indoor potted plant to the wild trees and shrubs on the edge of a thicket, we notice a vigorous straining toward the light. Each leaf is tilted at just the right angle to receive the largest possible share of energy, for the leaves are starch factories for which the sun furnishes the motive power.

Botanists tell us that this heliotropism or turning motion toward the light is due to the tendency of most leaves to arrange themselves perpendicularly to the sun’s rays. Tendrils may be apheliotropic or tend to turn away from the light. Morning Glories or Wistaria, which climb up whatever support is handy, exhibit insensibility to light no matter from what angle it strikes. Stems, flower and leaves of all plants each give a different and scientific reaction to light in a way which looks much like directing thought.

Nothing is more scientific than the skill with which plants co-operate with gravity in constructing their root systems. The roots are often trained to grow out horizontally and resist gravity for a certain distance. Then they gracefully yield to its pulling power, and, curving their tips downward, grow straight toward the center of the earth. Any secondary roots which are sent out again start horizontally to repeat the above process on a smaller scale. All this makes for an efficient, well-balanced root-system.

A curious motion which is not thoroughly understood is a slight gyratory movement observable in the tips of all living plants. It is possible that it is connected in some way with the earth’s rotation or is it merely a kind of groping, feeling gesture? In the case of roots, where the same gyrations occur, it undoubtedly serves that purpose. A revolving root tip makes a very efficient drill with which the hardy plant may bore a way through refractory soil. It is claimed that the great whirling sweeps made by tendrils of various climbers are merely amplifications of the circumnutation occurring in all plant terminals.