Cuar. XI.) GENERAL SUMMARY. 217 
placed on the glands of Drosera, the secretion, and that of 
the surrounding and untouched glands, was increased in 
quantity and became acid. But according to Schiff, the 
stomach of an animal does not secrete its proper ferment, 
pepsin, until certain substances, which he calls peptogenes, 
are absorbed; and it appears from my experiments that some 
matter must be absorbed by the glands of Drosera before 
they secrete their proper ferment. That the secretion does 
contain a ferment which acts only in the presence of an acid 
on solid animal matter, was clearly proved by adding minute 
doses of an alkali, which entirely arrested the process of 
digestion, this immediately recommencing as soon as the 
alkali was neutralised by a little weak hydrochloric acid. 
From trials made with a large number of substances, it was 
found that those which the secretion of Drosera dissolves 
completely, or partially, or not at all, are acted on in exactly 
the same manner by gastric juice. We may therefore con- 
clude that the ferment of Drosera is closely analogous to, or 
identical with, the pepsin of animals. 
The substances which are digested by Drosera act on the 
leaves very differently. Some cause much more energetic 
and rapid inflection of the tentacles, and keep them inflected 
for a much longer time, than do others. We are thus led to 
believe that the former are more nutritious than the latter, 
asis known to be the case with some of these same substances 
when given to animals; for instance, meat in comparison 
with gelatine. As cartilage is so tough a substance and is 
80 little acted on by water, its prompt dissolution by the 
secretion of Drosera, and subsequent absorption, is, perhaps, 
one of the most striking cases. But it is not really more 
remarkable than the digestion of meat, which is dissolved by 
this secretion in the same manner and by the same stages as 
by gastric juice. The secretion dissolves bone, and even the 
enamel of teeth, but this is simply due to the large quantity 
of acid secreted, owing, apparently, to the desire of the 
plant for phosphorus. In the case of bone, the ferment does 
not come into play until all the phosphate of lime has been 
decomposed and free acid is present, and then the fibrous 
basis is quickly dissolved. Lastly, the secretion attacks and 
dissolves matter out of living seeds, which it sometimes kills, 
or injures, as shown by the diseased state of the seedlings. It 
also absorbs matter from pollen, and from fragments of leaves. 
The seventh chapter was devoted to the action of the 
