numerous minute papillae, which absorb carbonate of ammonia, an infusion of raw meat, metallic salts, and probably many other substances, but the absorption of matter by these papillae never induces inflection.  We must remember that the movement of each separate tentacle depends on its gland being excited, except when a motor impulse is transmitted from the glands of the disc, and then the movement, as just stated, does not take place until some little time has elapsed.  I have made these remarks because they show us that when a leaf is immersed in a solution, and the tentacles are inflected, we can judge with some accuracy how much of the salt each gland has absorbed.  For instance, if a leaf bearing 212 glands be immersed in a measured quantity of a solution, containing 1/10 of a grain of a salt, and all the exterior tentacles, except twelve, are inflected, we may feel sure that each of the 200 glands can on an average have absorbed at most 1/2000 of a grain of the salt.  I say at [page 139] most, for the papillae will have absorbed some small amount, and so will perhaps the glands of the twelve excluded tentacles which did not become inflected.  The application of this principle leads to remarkable conclusions with respect to the minuteness of the doses causing inflection.

    On the Action of Distilled Water in Causing Inflection.

Although in all the more important experiments the difference between the leaves simultaneously immersed in water and in the several solutions will be described, nevertheless it may be well here to give a summary of the effects of water.  The fact, moreover, of pure water acting on the glands deserves in itself some notice.  Leaves to the number of 141 were immersed in water at the same time with those in the solutions, and their state recorded at short intervals of time.  Thirty-two other leaves were separately observed in water, making altogether 173 experiments.  Many scores of leaves were also immersed in water at other times, but no exact record of the effects produced was kept; yet these cursory observations support the conclusions arrived at in this chapter.  A few of the long-headed tentacles, namely from one to about six, were commonly inflected within half an hour after immersion; as were occasionally a few, and rarely a considerable number of the exterior round-headed tentacles.  After an immersion of from 5 to 8 hrs. the short tentacles surrounding the outer parts of the disc generally become inflected, so that their glands form a small dark ring on the disc; the exterior tentacles not partaking of this movement.  Hence, excepting in a few cases hereafter to be specified, we can judge whether a solution produces any effect only by observing the exterior tentacles within the first 3 or 4 hrs. after immersion.