Seth Mindwell.
DO PLANTS HAVE INSTINCT.
Instinct has been defined as a spontaneous impulse, especially in the lower animals—that moves them, without reasoning, toward actions that are essential to their existence, preservation and development. Instinct, imbedded in their organic structure, is the guide of animal life as reason is the guide of rational life. Instinct is said to be incapable of development and progress.
It is instinct that guides the wild goose in his long flight to meet the changing requirements of food and nesting. It is instinct that enables the carrier pigeon, though taken hoodwinked and by night to distant points, to wing his way unerringly homeward. Instinct leads the thrifty squirrel to stock his larder with nuts in anticipation of the period that must pass ere nuts are ripe again, and teaches him to destroy the embryo plant by biting out the germ so that his chestnuts will not sprout and thus be spoiled for food. The same wonderful power enables the bee to build her comb upon the strictest mathematical principles so as to obtain the greatest storage capacity and strength of structure with smallest consumption of wax, and then to store it with one of the most perfect and concentrated of foods. These and many other well-known cases of animal instinct will occur to the reader, but the object of this article is to mention a few phenomena of plant life, whereby they make, what we should designate in human beings, an intelligent adjustment to environment or provision for their future life and development.
As autumn approaches, even before Jack Frost strikes the first rude signal for winter quarters for insect and plant, or the wintry blasts compel the trees to furl sail and scud under bare poles, the forest trees begin to prepare for unfavorable conditions by forming and securely tucking away the bud that is next year to develop into leaf and flower. Before the leaf drops off, a substantial layer of cork is made to close up the pores through which the sap had so freely flowed during the growing season.
My older readers know, of course, that the green color of the leaf is due to the numerous corpuscles of chlorophyll which fill the cells. This same chlorophyll has an important mission to fulfill. These little green bodies are the only real food-making machines in nature. Upon the product of these tiny mills all animate nature depends for food. Their motive power is light, and their raw material the inorganic fluids absorbed by the roots from the soil, and their product is sugars and starches. It will be seen that chlorophyll is one of the most precious, as well as one of the rarest of substances, for while there may appear a great quantity it is superficial, never entering deeply into the substance of the plant.
The trees, by a sort of instinct, shall we say, withdraw their cohorts of green-liveried workers from the front as autumn approaches and deck themselves in the more gaudy but less wholesome colors of declining life. It is after the chlorophyll is withdrawn that the layer of cork is formed. The sturdy oak usually holds his brown leaves until they are whipped off by the wind.
The plants have been using light as a motive power for ages, while man, with his much-vaunted reason, is just beginning to utilize the kindred force, electricity, in arts and sciences. Man makes light draw a few pictures in sombre black and white, while nature flings broadcast landscape and life scenes in varied tints and shades.
In the process of photosynthesis much more energy is received than is necessary to run the machinery, so the plant, with commendable frugality, uses it in laying on what botanists call warming-up colors. If you will notice the peach twigs the next time you take a walk, you will see that the more tender shoots and the buds are decked in rich reds and browns. That this is not for mere ornament may be practically demonstrated by wrapping the bulbs of two similar thermometers, the one with a green leaf, the other with a brown or red leaf, say of begonia or beet. Then put the two in the sunlight and you will soon find a difference of from six to ten degrees in favor of the warming-up color. Speaking of buds, have you examined the horse chestnut bud? It is prepared for the winter in the most substantial manner. The future leaf is first wrapped in a quantity of finest silky wool, then a number of tough light green cases are put on, and this is followed by compact brown scales neatly overlapping, with a complete coating of wax, so that the interior is effectively protected from the cold and moisture. The use of the warming-up colors is quite common with plants.
In the far north the same plant that requires the whole long growing season to mature its seed, will crowd the whole process into a few weeks. It will suspend growth and all other processes, or run them on short time and devote itself almost entirely to producing seed, and the seed itself will have much thicker shell.