Secondly.—The head of a small pin, fixed into a handle, was dipped into the solution under trial. The small drop which adhered to it, and which was much too small to fall off, was cautiously placed, by the aid of a lens, in contact with the secretion surrounding the glands of one, two, three, or four of the exterior tentacles of the same leaf. Great care was taken that the glands themselves should not be touched. I had supposed that the drops were of nearly the same size; but on trial this proved a great mistake. I first measured some water, and removed 300 drops, touching the pin’s head each time on blotting-paper; and on again measuring the water, a drop was found to equal on an average about the 1/60 of a minim. Some water in a small vessel was weighed (and this is a more accurate method), and 300 drops removed as before; and on again weighing the water, a drop was found to equal on an average only the 1/89 of a minim. I repeated the operation, but endeavoured this time, by taking the pin’s head out of the water obliquely and rather quickly, to remove as large drops as possible; and the result showed that I had succeeded, for each drop on an average equalled 1/19.4 of a minim. I repeated the operation in exactly the same manner, and now the drops averaged 1/23.5 of a minim. Bearing in mind that on these two latter occasions special pains were taken to remove as large drops as possible, we may safely conclude that the drops used in my experiments were at least equal to the 1/20 of a minim, or .0029 ml. One of these drops could be applied to three or even four glands, and if the tentacles became inflected, some of the solution must have been absorbed by all; for drops of pure water, applied in the same manner, never produced any effect. I was able to hold the drop in steady contact with the secretion only for ten to fifteen seconds; and this was not time enough for the diffusion of all the salt in solution, as was evident, from three or four tentacles treated successively with the same drop, often becoming inflected. All the matter in solution was even then probably not exhausted. Thirdly.—Leaves cut off and immersed in a measured [page 138] quantity of the solution under trial; the same number of leaves being immersed at the same time, in the same quantity of the distilled water which had been used in making the solution. The leaves in the two lots were compared at short intervals of time, up to 24 hrs., and sometimes to 48 hrs. They were immersed by being laid as gently as possible in numbered watch-glasses, and thirty minims (1.775 ml.) of the solution or of water was poured over each.