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
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