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. Now was water absorbed from these five weak solutions, and yet, owing to the presence of the salts, did not prevent the subsequent action of the phosphate? Or [page 216] may we not suppose* that the interstices of the walls of the glands were blocked up with the molecules of these five substances, so that they were rendered impermeable to water; for had water entered, we know from the ten trials that the phosphate would not afterwards have produced any effect? It further appears that the molecules of the carbonate of ammonia can quickly pass into glands which, from having been immersed for 20 m. in a weak solution of sugar, either absorb the phosphate very slowly or are acted on by it very slowly. On the other hand, glands, however they may have been treated, seem easily to permit the subsequent entrance of the molecules of carbonate of ammonia. Thus leaves which had been immersed in a solution (of one part to 437 of water) of nitrate of potassium for 48 hrs.—of sulphate of potassium for 24 hrs.—and of the chloride of potassium for 25 hrs.—on being placed in a solution of one part of carbonate of ammonia to 218 of water, had their glands immediately blackened, and after 1 hr. their tentacles somewhat inflected, and the protoplasm aggregated. But it would be an endless task to endeavour to ascertain the wonderfully diversified effects of various solutions on Drosera.
Alcohol (one part to seven of water).—It has already been shown that half-minims of this strength placed on the discs of leaves do not cause any inflection; and that when two days afterwards the leaves were given bits of meat, they became strongly inflected. Four leaves were immersed in this mixture, and two of them after 30 m. were brushed with a camel-hair brush, like the leaves in the solution of camphor, but this produced no effect.