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 are highly poisonous to animals, are equally so to Drosera.  But it is a singular fact that the chloride of lead and two salts of barium were not poisonous to this plant.  It is an equally strange fact, that, though acetic and propionic acids are highly poisonous, their ally, formic acid, is not so; and that, whilst certain vegetable acids, namely oxalic, benzoic, &c., are poisonous in a high degree, gallic, tannic, tartaric, and malic (all diluted to an equal degree) are not so.  Malic acid induces inflection, whilst the three other just named vegetable acids have no such power.  But a pharmacopoeia would be requisite to describe the diversified effects of various substances on Drosera.

* Dr. Fayrer, ‘The Thanatophidia of India,’ 1872, p. 4.

  Seeing that acetic, hydrocyanic, and chromic acids, acetate of
  strychnine, and vapour of ether, are poisonous to Drosera, [[page
225]] it is remarkable that Dr. Ransom (’ Philosoph.  Transact.’ 1867, p. 480), who used much stronger solutions of these substances than I did, states “that the rhythmic contractility of the yolk (of the ova of the pike) is not materially influenced by any of the poisons used, which did not act chemically, with the exception of chloroform and carbonic acid.”  I find it stated by several writers that curare has no influence on sarcode or protoplasm, and we have seen that, though curare excites some degree of inflection, it causes very little aggregation of the protoplasm.) [page 225]

Of the alkaloids and their salts which were tried, several had not the least power of inducing inflection; others, which were certainly absorbed, as shown by the changed colour of the glands, had but a very moderate power of this kind; others, again, such as the acetate of quinine and digitaline, caused strong inflection.

The several substances mentioned in this chapter affect the colour of the glands very differently.  These often become dark at first, and then very pale or white, as was conspicuously the case with glands subjected to the poison of the cobra and citrate of strychnine.  In other cases they are from the first rendered white, as with leaves placed in hot water and several acids; and this, I presume, is the result of the coagulation of the albumen.  On the same leaf some glands become white and others dark-coloured, as occurred with leaves in a solution of the sulphate of quinine, and in the vapour of alcohol.  Prolonged immersion in nicotine, curare, and even water, blackens the glands;