The endocrine system, essentially

Usage examples of glands.

A plant of Drosera, with the edges of its leaves curled inwards, so as to form a temporary stomach, with the glands of the closely inflected tentacles pouring forth their acid secretion, which dissolves animal matter, afterwards to be absorbed, may be said to feed like an animal.

The purple fluid or granular matter which fills the cells of the glands differs to a certain extent from that within the cells of the pedicels.

Number of insects captured--Description of the leaves and their appendages or tentacles--Preliminary sketch of the action of the various parts, and of the manner in which insects are captured--Duration of the inflection of the tentacles--Nature of the secretion--Manner in which insects are carried to the centre of the leaf--Evidence that the glands have the power of absorption--Small size of the roots.

Inflection of the exterior tentacles owing to the glands of the disc being excited by repeated touches, or by objects left in contact with them--Difference in the action of bodies yielding and not yielding soluble nitrogenous matter--Inflection of the exterior tentacles directly caused by objects left in contact with their glands--Periods of commencing inflection and of subsequent reexpansion--Extreme minuteness of the particles causing inflection--Action under water--Inflection of the exterior tentacles when their glands are excited by repeated touches--Falling drops of water do not cause inflection.

There is, however, a narrow zone close beneath the glands of the longer tentacles, and a broader zone near their bases, of a green tint.

Whatever their function may be, they are not necessary for the secretion of a digestive fluid, or for absorption, or for the communication of a motor impulse to other parts of the leaf, as we may infer from the structure of the glands in some other genera of the Droseraceae.

Their glands are much elongated, and lie embedded on the upper surface of the pedicel, instead of standing at the apex.

A living insect is a more efficient object than a dead one, as in struggling it presses against the glands of many tentacles.

If the glands on the disc are repeatedly touched or brushed, although no object is left on them, the marginal tentacles curve inwards.

So again, if drops of various fluids, for instance of saliva or of a solution of any salt of ammonia, are placed on the central glands, the same result quickly follows, sometimes in under half an hour.

The secretion from the glands is extremely viscid, so that it can be drawn out into long threads.

It is a much more remarkable fact that when an object, such as a bit of meat or an insect, is placed on the disc of a leaf, as soon as the surrounding tentacles become considerably inflected, their glands pour forth an increased amount of secretion.

We must therefore conclude that the central glands, when strongly excited, transmit some influence to the glands of the circumferential tentacles, causing them to secrete more copiously.

As soon as tentacles, which have remained closely inflected during several days over an object, begin to reexpand, their glands secrete less freely, or cease to secrete, and are left dry.

After the reexpansion is complete, the glands quickly begin to resecrete, and as soon as fullsized drops are formed, the tentacles are ready to clasp a new object.