CARNIVOROUS PLANTS, plants of various genera which subsist partly upon insects and other small animals which they entrap in various ways. The apparatus in each case is a modified leaf or part of a leaf, and in some cases the modifications are so curious, so well adapted to the use to which they are put, and so perfect in action that the plants seem al most intelligent. The object sought by these plants seems to be to supply themselves with nitrogenous food, which is generally in meagre supply where they usually live — undrained swamps. Probably, too, such carnivorous plants as do not live in these habitats for merly did, but have not yet lost the use of the apparatus. A case of this kind is exhibited by the genus Utricularia (see BLADDERWORT). In this genus various species provided with active bladders, which act like eel-traps, live sub merged in ponds; other species, also possess ing active but less perfect and useful traps, live in the marshy soil of swamps. Still others live on dry ground, but these have usually abortive traps. The conclusion is that as the ponds be came swamps, and the swamps were converted into dry land, the supply of nitrogenous food increased, and hence the traps became aborted, because they were no longer needed.
Probably the most nearly intelligent of these carnivorous plants is the Venus' fly-trap (Dioncra), found in North Carolina. The trap
(leaf-blade) consists of two pieces hinged together. On the margins are bristles, and in the interior a few sensitive hairs, which, when touched, act like a trigger, and the apparatus closes. Should an insect cause this, action the bristles will prevent its escape and the trap will remain closed until digestion is complete, when it will open, cast out the indigestible portions and be ready for another victim. If the trap fails to catch its prey, or if it be sprung by something it cannot utilize, it will open again in a short time. In the sundew (Drosera) the leaves are not provided with glandular hairs, which close over the insect that alights upon the leaf, and a glistening sticky substance holds it fast until its digestible parts are absorbed by the plant.
In the pitcher-plants (Sarracenia, Nepen thes), the pitcher consists of a tube-like leaf either with or without a lid or hood. Around the mouth there is usually a sugary secretion which acts as a lure. The insect that alights cannot escape because the tube is lined with hairs that force him downward to the bottom of the tube, which is usually partly filled with water. Some other genera in which the carniv orous habit is developed are Darlingtonia, Aldrovandra and Pingescuta. Consult Darwin, 'Insectivorous Plants.'