Twelve leaves were tried as before in a solution of one part to 175,000 of water (1 gr. to 400 oz.), so that each leaf received 1/6400 of a grain (.0101 mg.). My plants were not at the time in a good state, and many of the leaves were young and pale. Nevertheless, two of them had all their tentacles, except three or four, closely inflected in under 1 hr. Seven were considerably affected, some within 1 hr., and others not until 3 hrs., 4 hrs. 30 m., and 8 hrs. had elapsed; and this slow action may be attributed to the leaves being young and pale. Of these nine leaves, four had their blades well inflected, and a fifth slightly so. The three remaining leaves were not affected. With respect to the twelve corresponding leaves in water, not one had its blade inflected; after from 1 to 2 hrs. one had thirteen of its outer tentacles inflected; a second six, and four others either one or two inflected. After 8 hrs. the outer tentacles did not become more inflected; whereas this occurred with the leaves in the solution. I record in my notes that [page 158] after the 8 hrs. it was impossible to compare the two lots, and doubt for an instant the power of the solution. Two of the above leaves in the solution had all their tentacles, except three and four, inflected within an hour. I counted their glands, and, on the same principle as before, each gland on one leaf could have absorbed only 1/1164800, and on the other leaf only 1/1472000, of a grain of the phosphate. Twenty leaves were immersed in the usual manner, each in thirty minims of a solution of one part to 218,750 of water (1 gr. to 500 oz.). So many leaves were tried because I was then under the false impression that it was incredible that any weaker solution could produce an effect. Each leaf received 1/8000 of a grain, or .0081 mg. The first eight leaves which I tried both in the solution and in water were either young and pale or too old; and the weather was not hot. They were hardly at all affected; nevertheless, it would be unfair to exclude them. I then waited until I got eight pairs of fine leaves, and the weather was favourable; the temperature of the room where the leaves were immersed varying from 75° to 81° (23°.8 to 27°.2 Cent.) In another trial with four pairs (included in the above twenty pairs), the temperature in my room was rather low, about 60° (15°.5 Cent.); but the plants had been kept for several days in a very warm greenhouse and thus rendered extremely sensitive. Special precautions were taken for this set of experiments; a chemist weighed for me a grain in an excellent balance; and fresh water, given me by Prof. Frankland, was carefully measured. The leaves were selected from a large number of plants in the following manner: the four finest were immersed in water, and the next four finest in the solution, and so on till the twenty pairs were complete. The water specimens were thus a little favoured, but they did not undergo more inflection than in the previous cases,