224 DROSERA ROTUNDIFOLIA. Cnae. IX, 
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 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 pharmacopeia would be requisite to describe the 
diversified effects of various substances on Drosera.f 
* Dr. Fayrer, ‘The Thanato-  cyanic, and chromic acids, ace- 
phidia of India.’ 1872, p. 4. tate of strychnine, and vapour of 
+ Secing that acetic, hydro- ether, are poisonous to Drosera, 
