218 DROSERA ROTUNDIFOLIA. [Chap. XI. 



fluence to the glands of the exterior tentacles, causing them 

 to secrete more copiously and the secretion to become acid, 

 as if they had been directly excited by an object placed on 

 them. The gastric juice of animals contains, as is well 

 known, an acid and a ferment, both of which are indis- 

 pensable for digestion, and so it is with the secretion of 

 Drosera. When the ptomach of an animal is mechanically 

 irritated, it secretes an acid, and when particles of glass or 

 other such objects were placed on the glands of Drosera, the 

 secretion, and that of the surrounding and untouched 

 glands, was increased in quantity and became acid. But ac- 

 cording 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 recom- 

 mencing 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 conclude that the ferment of Drosera is close- 

 ly 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, 

 as is 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 

 so little acted on by water, its prompt dissolution by the se- 

 cretion 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 



