220 DROSERA ROTUNDIFOLIA. (Cuar. XI. 
strictly with their chemical affinities, as inferred from the 
classification commonly followed. The nature of the base is 
far more influential than that of the acid; and this is known 
to hold good with animals. For instance, nine salts of 
sodium all caused well-marked inflection, and none of them 
were poisonous in small doses; whereas seven of the nine 
corresponding salts of potassium produced no effect, two 
causing slight inflection. Small doses, moreover, of some of 
the latter salts were poisonous. The salts of sodium and 
potassium, when injected into the veins of animals, likewise 
differ widely in their action. The so-called earthy salts 
produce hardly any effect on Drosera. On the other hand, 
most of the metallic salts cause rapid and strong inflection, 
and are highly poisonous; but there are some odd exceptions 
to this rule; thus chloride of lead and zinc, as well as two 
salts of barium, did not cause inflection, and were not 
poisonous. 
Most of the acids which were tried, though much diluted 
(one part to 437 of water), and given in small doses, acted 
powerfully on Drcsera; nineteen, out of the twenty-four, 
causing the tentacles to be more or less inflected. Most of 
them, even the organic acids, are poisonous, often highly so; 
and this is remarkable, as the juices of so many plants 
contain acids. Benzoic acid, which is innocuous to animals, 
seems to be as poisonous to Drosera as hydrocyanic. On the 
other hand, hydrochloric acid is not poisonous either to 
animals or to Drosera, and induces only a moderate amount 
of inflection, Many acids excite the glands to secrete an 
extraordinary quantity of mucus; and the protoplasm 
within their cells seems to be often killed, as may be inferred 
from the surrounding fluid soon becoming pink. It is 
strange that allied acids act very differently: formic acid 
induces very slight inflection, and is not poisonous; whereas 
acetic acid of the same strength acts most powerfully and is 
poisonous. Lactic acid is also poisonous, but causes inflection 
only after a considerable lapse of time. Malic acid acts 
slightly, whereas citric and tartaric acids produce no effect. 
In the ninth chapter the effects of the absorption of 
various alkaloids and certain other substances were de- 
scribed. Although some of these are poisonous, yet as 
several, which act powerfully on the nervous system of 
animals, produce no effect on Drosera, we may infer that the 
extreme sensibility of the glands, and their power of trans- 
