Page:Popular Science Monthly Volume 30.djvu/194

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voluntary celibacy for those who overtax their vital energies by an intellectual strain that hurts the offspring; and in the honoring of those lighter and easier methods of making money which have hitherto condemned a woman to social ostracism, and denied her the status she deserves and has inherited.—Fortnightly Review.


By Professor T. H. McBRIDE.

FEW people have any true conception either of the kind or amount of actual energy displayed in the life and growth of a simple plant. In ordinary experience the manifestations of vital energy are always associated with the activity of some animal. Life in the animal seems at its best; its forces are more concentrated, hence more vivid in display, and in every way appeal more certainly to our attention. An animal can move, can exhibit strength, can do work, hence has force, exhibits energy—vital energy, if you please. But in the plant-world these forces are less noted, although going on in much the same way to the accomplishment of life's purposes; and, if less obtrusive in their action and simpler in behavior, are also less difficult to study and easier to understand. To see where some of these forces are exerted, how they are manifested and how controlled, is, in so far as circumstances may allow, the purpose of this article.

The most patent display of energy on the part of a plant is in connection with the growth. Every one knows how a growing seed will send a shoot to the surface through a hard covering of overlying earth. And above-ground the tip of the growing plantlet persistently defies gravitation. Roots find their way through the interstices of clay, and crowd into the enlarging crevices of rocks. The bark of a tree, under tension, in equilibrium of pressure and resistance as long as the tree lives, evinces an energy very appreciable in amount. The amount of force concerned in this case we are not left to imagine, but may at least approximately estimate.

Along the highway that passes one of our Iowa farms were planted many years ago a row of soft-maple trees, designed to serve at length as posts for carrying the wires of the fence. When the trees attained suitable size they were put to the use intended by nailing to each tree a piece of pine lumber four feet long and two by four inches in section for the better attachment of the wires. Since the erection of the fence in the way indicated, the growth of the trees has produced some very striking results. The blocks were attached to the trees by heavy iron spikes (Fig. 1). These seem to have rusted into the tree, and by their points to have held firmly, while by the continual deposition of