Half-minims of a rather weaker solution, viz. of one part to 1312 of water (1 gr. to 3 oz.) were tried on fourteen leaves; so that each received 1/2880 of a grain (.0225 mg.), instead of, as in the last experiment, 1/2400 of a grain. The blade of one was plainly inflected, as were six of the exterior tentacles; the blade of a second was slightly, and two of the exterior tentacles well, inflected, all the other tentacles being curled in at right angles to the disc; three other leaves had from five to eight tentacles inflected; five others only two or three, and occasionally, though very rarely, drops of pure water cause this much action; the four remaining leaves were in no way affected, yet three of them, when subsequently tried with urine, became greatly inflected. In most of these cases a slight effect was perceptible in from 6 hrs. to 7 hrs., but the full effect was not produced until from 24 hrs. to 30 hrs. had elapsed. It is obvious that we have here reached very nearly the minimum amount, which, distributed between the glands of the disc, acts on the exterior tentacles; these having themselves not received any of the solution. In the next place, the viscid secretion round three of the exterior glands was touched with the same little drop (1/20 of a minim) of a solution of one part to 437 of water; and after an interval of 2 hrs. 50 m. all three tentacles were well inflected. Each of these glands could have received only the 1/28800 of a grain, or .00225 mg. A little drop of the same size and strength was also applied to four other glands, and in 1 hr. two became inflected, whilst the other two never moved. We here see, as in the case of the half-minims placed on the discs, that the nitrate of ammonia is more potent in causing inflection than the carbonate; for minute drops of the latter salt of this strength produced no effect. I tried minute drops of a still weaker solution of the nitrate, viz. one part to 875 of water, on twenty-one glands, but no effect whatever was produced, except perhaps in one instance. Sixty-three leaves were immersed in solutions of various strengths; other leaves being immersed at the same time in the same pure water used in making the solutions. The results are so remarkable, though less so than with phosphate of ammonia, that I must describe the experiments in detail, but I will give only a few. In speaking of the successive periods when inflection occurred, I always reckon from the time of first immersion. [page 150]