recover its sensibility whilst still in the solution, which from having
been made with distilled water probably contained little oxygen.]
Concluding Remarks on the Effects of the foregoing Agents. As the
glands, when excited, transmit some influence to the surrounding
tentacles, causing them to bend and their glands to pour forth an
increased amount of modified secretion, I was anxious to ascertain
whether the leaves included any element having the nature of
nerve-tissue, which, though not continuous, served as the channel of
transmission. This led me to try the several alkaloids and other
substances which are known to exert a powerful influence on the nervous
system of animals; I was at first encouraged in my trials by finding
that strychnine, digitaline, and nicotine, which all act on the nervous
system, were poisonous to Drosera, and caused a certain amount of
inflection. Hydrocyanic acid, again, which is so deadly a poison to
animals, caused rapid movement of the tentacles. But as several
innocuous acids, though much diluted, such as benzoic, acetic, &c., as
well as some essential oils, are extremely poisonous to Drosera, and
quickly cause strong inflection, it seems probable that strychnine,
nicotine, digitaline, and hydrocyanic acid, excite inflection by acting
on elements in no way analogous to the nerve-cells of animals. If
elements of this latter nature had been present in the leaves, it might
have been expected that morphia, hyoscyamus, atropine, veratrine,
colchicine, curare, and diluted alcohol would have produced some marked
effect; whereas [page 224] these substances are not poisonous and have
no power, or only a very slight one, of inducing inflection. It should,
however, be observed that curare, colchicine, and veratrine are
muscle-poisons that is, act on nerves having some special relation with
the muscles, and, therefore, could not be expected to act on Drosera.
The poison of the cobra is most deadly to animals, by paralysing their
nerve-centres,* yet is not in the least so to Drosera, though quickly
causing strong inflection.
Notwithstanding the foregoing facts, which show how widely different is
the effect of certain substances on the health or life of animals and
of Drosera, yet there exists a certain degree of parallelism in the
action of certain other substances. We have seen that this holds good
in a striking manner with the salts of sodium and potassium. Again,
various metallic salts and acids, namely those of silver, mercury,
gold, tin, arsenic, chromium, copper, and platina, most or all of which
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