a second was slightly affected; the inflection subsequently increased, though slowly. Hence diluted alcohol, which, as we shall see, is hardly at all poisonous, plainly retards the subsequent action of the phosphate.

It was shown in the last chapter that leaves which did not become inflected by nearly a day's immersion in solutions of various salts and acids behaved very differently from one another when subsequently placed in the phosphate solution. I here give a table summing up the results.

Column 1 : Name of the Salts and Acids in Solution. Column 2 : Period of Immersion of the Leaves in Solutions of one part to 437 of water. Column 3 : Effects produced on the Leaves by their subsequent Immersion for stated periods in a Solution of one part of phosphate of ammonia to 8750 of water, or 1 gr. to 20 oz.

Rubidium chloride. : 22 hrs. : After 30 m. strong inflection of the tentacles.

Potassium carbonate : 20 m. : Scarcely any inflection until 5 hrs. had elapsed.

Calcium acetate. : 24 hrs. : After 24 hrs. very slight inflection.

Calcium nitrate. : 24 hrs. : Do. do.

Magnesium acetate. : 22 hrs. : Some slight inflection, which became well pronounced in 24 hrs.

Magnesium nitrate. : 22 hrs. : After 4 hrs. 30 m. a fair amount of inflection, which never increased.

Magnesium chloride : 22 hrs. : After a few minutes great inflection; after 4 hrs. all four leaves with almost every tentacle closely inflected.

Barium acetate. : 22 hrs. : After 24 hrs. two leaves out of four slightly inflected.

Barium nitrate. : 22 hrs. : After 30 m. one leaf greatly, and two others moderately, inflected; they remained thus for 24 hrs.

Strontium acetate. : 22 hrs. : After 25 m. two leaves greatly inflected; after 8 hrs. a third leaf moderately, and the fourth very slightly, inflected. All four thus remained for 24 hrs.

Strontium nitrate. : 22 hrs. : After 8 hrs. three leaves out of five moderately inflected; after 24 hrs. all five in this state; but not one closely inflected.

Aluminium chloride : 24 hrs. : Three leaves which had either been slightly or not at all affected by the chloride became after 7 hrs. 30 m. rather closely inflected. [page 215]

Column 1 : Name of the Salts and Acids in Solution. Column 2 : Period of Immersion of the Leaves in Solutions of one part to 437 of water. Column 3 : Effects produced on the Leaves by their subsequent Immersion for stated periods in a Solution of one part of phosphate of ammonia to 8750 of water, or 1 gr. to 20 oz.

Aluminium nitrate. : 24 hrs. : After 25 hrs. slight and doubtful effect.

Lead chloride. : 23 hrs. : After 24 hrs. two leaves somewhat inflected, the third very little; and thus remained.

Manganese chloride : 22 hrs. : After 48 hrs. not the least inflection.

Lactic acid. : 48 hrs. : After 24 hrs. a trace of inflection in a few tentacles, the glands of which had not been killed by the acid.

Tannic acid. : 24 hrs. : After 24 hrs. no inflection.

Tartaric acid. : 24 hrs. : Do. do.

Citric acid. : 24 hrs. : After 50 m. tentacles decidedly inflected, and after 5 hrs. strongly inflected; so remained for the next 24 hrs.

Formic acid. : 22 hrs. : Not observed until 24 hrs. had elapsed; tentacles considerably inflected, and protoplasm aggregated.

In a large majority of these twenty cases, a varying degree of inflection was slowly caused by the phosphate. In four cases, however, the inflection was rapid, occurring in less than half an hour or at most in 50 m. In three cases the phosphate did not produce the least effect. Now what are we to infer from these facts? We know from ten trials that immersion in distilled water for 24 hrs. prevents the subsequent action of the phosphate solution. It would, therefore, appear as if the solutions of chloride of manganese, tannic and tartaric acids, which are not poisonous, acted exactly like water, for the phosphate produced no effect on the leaves which had been previously immersed in these three solutions. The majority of the other solutions behaved to a certain extent like water, for the phosphate produced, after a considerable interval of time, only a slight effect. On the other hand, the leaves which had been immersed in the solutions of the chloride of rubidium and magnesium, of acetate of strontium, nitrate of barium, and citric acid, were quickly acted on by the phosphate.

Charles Darwin

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