there was no inflection. I then added, for the sake of testing the leaves, some strong solution (viz. 1 gr. to 20 oz., or one part to 8750 of water) of phosphate of ammonia, and all four became in 30 m. closely inflected.

Lithium, Nitrate of.--Four leaves were immersed, as in the last case, in 120 minims of a solution of one part to 437 of water; after 1 h. 30 m. all four were a little, and after 24 hrs. greatly, inflected. I then diluted the solution with some water, but they still remained somewhat inflected on the third day.

Caesium, Chloride of.--Four leaves were immersed, as above, in 120 minims of a solution of one part to 437 of water. After 1 hr. 5 m. the glands were darkened; after 4 hrs. 20 m. there was a trace of inflection; after 6 hrs. 40 m. two leaves were greatly, but not closely, and the other two considerably inflected. After 22 hrs. the inflection was extremely great, and two had their blades inflected. I then transferred the leaves into water, and in 46 hrs. from their first immersion they were almost re-expanded.

Rubidium, Chloride of.--Four leaves which were immersed, as above, in 120 minims of a solution of one part to 437 of water, were not acted on in 22 hrs. I then added some of the strong solution (1 gr. to 20 oz.) of phosphate of ammonia, and in 30 m. all were immensely inflected.

Silver, Nitrate of.--Three leaves were immersed in ninety [page 182] minims of a solution of one part to 437 of water; so that each received, as before, 1/16 of a grain. After 5 m. slight inflection, and after 11 m. very strong inflection, the glands becoming excessively black; after 40 m. all the tentacles were closely inflected. After 6 hrs. the leaves were taken out of the solution, washed, and placed in water; but next morning they were evidently dead.

Calcium, Acetate of.--Four leaves were immersed in 120 minims of a solution of one part to 437 of water; after 24 hrs. none of the tentacles were inflected, excepting a few where the blade joined the petiole; and this may have been caused by the absorption of the salt by the cut-off end of the petiole. I then added some of the solution (1 gr. to 20 oz.) of phosphate of ammonia, but this to my surprise excited only slight inflection, even after 24 hrs. Hence it would appear that the acetate had rendered the leaves torpid.

Calcium, Nitrate of.--Four leaves were immersed in 120 minims of a solution of one part to 437 of water, but were not affected in 24 hrs. I then added some of the solution of phosphate of ammonia (1 gr. to 20 oz.), but this caused only very slight inflection after 24 hrs. A fresh leaf was next put into a mixed solution of the above strengths of the nitrate of calcium and phosphate of ammonia, and it became closely inflected in between 5 m. and 10 m. Half-minims of a solution of one part of the nitrate of calcium to 218 of water were dropped on the discs of three leaves, but produced no effect.

Magnesium, Acetate, Nitrate, and Chloride of.--Four leaves were immersed in 120 minims of solutions, of one part to 437 of water, of each of these three salts; after 6 hrs. there was no inflection; but after 22 hrs. one of the leaves in the acetate was rather more inflected than generally occurs from an immersion for this length of time in water. Some of the solution (1 gr. to 20 oz.) of phosphate of ammonia was then added to the three solutions. The leaves in the acetate mixed with the phosphate underwent some inflection; and this was well pronounced after 24 hrs. Those in the mixed nitrate were decidedly inflected in 4 hrs. 30 m., but the degree of inflection did not afterwards much increase; whereas the four leaves in the mixed chloride were greatly inflected in a few minutes, and after 4 hrs. had almost every tentacle closely inflected. We thus see that the acetate and nitrate of magnesium injure the leaves, or at least prevent the subsequent action of phosphate of ammonia; whereas the chloride has no such tendency. [page 183]

Magnesium, Sulphate of.--Half-minims of a solution of one part to 218 of water were placed on the discs of ten leaves, and produced no effect.

Charles Darwin

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