Open main menu

Page:Popular Science Monthly Volume 65.djvu/430

This page has been validated.

one has become entangled all the hairs will take part in the movement, and even the blade of the leaf may be bent together in such a way as to aid in the aggregation of the tips. The globules of jelly fuse into a mass about the insect and there is poured out from the glands a digestive juice such as that in the East Indian pitcher-plant and the butterwort. All the soft parts of the insect are digested and the nutritive juices, rich in nitrogen, are absorbed by the very same glands which secreted the digestive juice.

It is obvious that the aggregation of the hairs causes a more complete surrounding of the insect with jelly, increases the amount of digestive juice brought to act upon it, and also the number of channels for conducting the juices back into the leaf. The movements here involved PSM V65 D430 Cup of east indian pitcher plant.pngFig. 9. The Cup of Another Species of East Indian Pitcher-plant. Note the two directive wings on the outside and the ridge just inside the mouth.are comparatively rapid—the hairs nearest the one which has made a capture begin to move in five seconds; if the capture is a big one all the hairs will be aggregated about it in half an hour. The time required for the digestion of prey depends entirely upon its size and nature; when completed the jelly dries off from the glands, the hard indigestible parts of the insect blow away, and the hairs resume their usual positions. The globules of jelly are then renewed and the leaf is ready for another capture. A single leaf may partake of above one hundred such meals, but more commonly its life is shorter, its place being rapidly taken by a younger leaf.

These are highly complex structures with which we meet in the sun-dew, and the united action of the hairs in aggregating themselves towards the spot where an insect has alighted is an example of coordinated activity such as is rarely met with in the plant world. There are, however, no unusual structures here, there is nothing in any way resembling a nervous system and nothing suggesting any similarity to the coordinated movements of animals which they so closely resemble. The most highly developed and remarkable of the insectivorous plants is the Venus' fly-trap (Dionæa), which will never cease to be the cardinal attraction with all florists so fortunate as to be able to