238 Vines. — Proteolytic Enzymes in Plants. 
Apple (. Ananas sativus ), and of certain laticiferous plants such 
as the Papaw ( Carica Papaya) and the Fig ( Ficus Carica). In 
all these cases the process includes both the peptonization of 
the more complex proteids and the proteolysis of the simpler 
proteids. 
I would recall the suggestion made years ago by Claude 
Bernard and by Sachs, that a digestive enzyme may be 
presumed to be formed in all organs, such as seeds, fruits, 
bulbs, tubers, &c., in which proteids are stored. This sugges- 
tion has already been fully verified in the case of seeds : 
indeed the ascertained facts warrant the inference that a 
digestive enzyme is produced in all germinating seeds. The 
object that I had in view, on commencing these investigations, 
was to supply similar verification in the other cases, and so to 
add to the number of known instances of the occurrence of 
these enzymes in plants. I have, however, carried them far 
beyond these prescribed limits and in an unexpected direction, 
as the following pages will show. 
It has been customary, in investigations of this sort, to 
employ relatively intractable proteids (using the word in 
a quite general sense), either blood-fibrin or coagulated egg- 
albumin, as the digestible material ; and the tests subse- 
quently applied have been the biuret-test and others which 
indicate the presence of the lower proteids, viz. albumoses 
and peptones. That is to say, the investigation has been 
directed to the question as to whether or not a peptonizing 
enzyme was present. The methods that I have adopted are 
quite different to these. In the first place, it has to be borne 
in mind that the enzymes in the tissues of plants are not 
called upon to digest fibrin and egg-albumin. It is true that 
in several cases (e.g. Pine-Apple, Papaw, Fig, Yeast) enzymes 
have been found which are capable of digesting these sub- 
stances : but it does not follow, as seems to have been 
generally assumed, that because a vegetable juice or extract 
cannot digest them, it therefore contains no enzyme at all. 
As I long ago pointed out (3), the proteids of plants are 
chiefly globulins and albumoses : it is therefore obvious that 
