io6 Green. — On Vegetable Ferments. 
genous matter, is placed upon a leaf of Drosera , the glands 
quickly exude a somewhat viscid slightly acid fluid, at the 
same time bending over to imprison the stimulating matter. 
The surface and margins of the leaves are alike provided with 
stalked glands, the secretion of the central ones being more 
acid than that of those at the periphery. Darwin considered 
the acid to be propionic, or else a mixture of acetic and 
butyric acids. The ferment of the secretion acting in the 
acid medium dissolves the nitrogenous body imprisoned by 
the glands. Besides proteid matters, it can dissolve con- 
nective tissue, cartilage, and gelatin ; but it has no action on 
mucin. Besides resembling animal pepsin in the medium 
in which it works and in the decompositions it effects as just 
described, it is much like it in the conditions of its secretion, 
being found in the exuded fluid only when the glands have 
been stimulated by the absorption of nitrogenous matter. 
The acid of the juice of Drosera is only developed under the 
same conditions. 
Darwin discovered that the same ferment exists also in the 
leaves of Dionaea. These differ in the arrangement of their 
glands from those of Drosera ; the leaves have their upper 
surfaces covered with small almost sessile secreting glands 
of a purplish colour. Like the leaves of Drosera , those of 
Dionaea do not secrete anything until they are excited by 
the absorption of nitrogenous matter. Then they pour out 
a fluid which is colourless and slightly mucilaginous. It is 
more acid than that of Drosera , and acts like the latter on 
albumin. Pinguicula also secretes a similar body on the 
edges of the upper surface of the leaf which folds over to 
enclose its captives. 
To von Gorup-Besanez 1 and to Vines 2 we are indebted for 
our knowledge of the powers of the liquid in the pitchers of 
Nepenthes. The former established the fact that the fluid 
could dissolve fibrin when the latter was placed in it and 
kept for an hour at a temperature of 40° C., the solution giving 
the biuret reaction characteristic of peptone. The exact 
1 op. cit. 2 op. cit. 
