Page:Popular Science Monthly Volume 30.djvu/705

Rh Only after Darwin had made his researches were they recalled, and at once commanded the interest of naturalists to such a degree that, at present, there are known over three hundred plants that feed on insects. They belong to various families, and are found in all parts of the globe. But how can the firmly rooted plant capture and grasp the light-winged insect; how can it retain the same sufficiently long to let the digestive juices act upon it? Naturally, in many cases, the sticky substance which is secreted by the leaves is the active agent, as, for instance, one may observe small animals adhering to the resinous stem of the "flytrap." But many plants are provided with special organs for this purpose, and they are able to catch the most nimble of insects with ease and dispatch.

One of the best known of these insect-eating plants found here, as well as in Lapland and Scandinavia, is the Sun-dew (Drosera), discovered about a century ago. Another plant, the so-called Flytrap of Venus (Dionæa) of America, which was brought to England one hundred and twenty years ago, has received the name of Venus for the reason that, like the goddess of Beauty, it attracts and captivates everything that heedlessly approaches it. At the bottom of the plant the leaves cluster like a rosette; from the center of this arises the flower-stalk. The edge of the leaf, which is nearly circular, is overgrown with strong bristles, while its surface is covered with small glands, at either side of which are three long hairs. A fly approaches; carelessly it settles on the leaf, and perchance touches one of the six long hairs: suddenly the leaf folds, the bristles interlace, and the insect is caught. Oftentimes the whole tragedy takes but ten seconds. The sensitive hairs have performed their duty; now begins the work of the glands. These discharge a large quantity of a colorless acid slime—the digestive fluid, pepsin—and the closed leaf changes at once into a stomachic organ. After a lapse of eight or nine days the leaf reopens, the insect has disappeared, the prey has been consumed. The above-mentioned facts constitute the main features of the process of digestion, but in connection with it many questions arise. What happens, for instance, if a non-edible object irritate the hairs, perhaps a stone or a piece of wood? The leaf closes with the greatest possible swiftness, but soon discovers its mistake, and does not discharge the digestive juice; after a lapse of twenty-four hours it again unfolds, ready for another capture. This does away with the marks of distinction thus far generally accepted, namely, that "plants live, animals live and feel" (plantæ vivunt, animalia vivunt et sentiunt), for the Dionæa distinguishes quite readily, by taste and feeling, that which is digestible from that which is not. By experiment, it has been ascertained that nitrogenous nourishment is preferred by the Dionæa; hence every kind of meat (beef, pork, and veal, either raw, fried, or stewed) is digested by the plant; also albumen and cheese; the latter, however, causes disturbances during digestion, and the leaf easily ails. If