3 1 6 
Vines. — The Proteases of Plants . 
extended investigations in this direction ; but what already I have done is, 
I think, of sufficient interest to be mentioned here. 
In a previous paper (13, p. 254), I gave an account of some peptonizing 
experiments with the bulbs of the hyacinth, the tulip, and the onion, the 
bruised bulb-tissue being employed. The results were not conclusive, but 
indicated that whilst the onion did not digest fibrin, the hyacinth and the 
tulip did so to some extent in a slightly alkaline liquid. 
I have since resumed these experiments, using watery or NaCl 
extracts of the bulbs, and taking the disappearance of a small quantity 
of fibrin as the test of digestion, following the method adopted in the 
investigation of the yeast and the mushroom, with interesting results. 
Experiment 1. A hyacinth bulb, weighing about 75 grms., was reduced to 
pulp and extracted for two hours with 100 cc. of 2 % NaCl solution : the liquid was 
strained through muslin. 30 cc. were put into each of 3 bottles with o 2 grm. fibrin 
and some toluol : to No. 1, nothing further was added ; to No. 2, HC 1 to on % ; to 
No. 3, Na 2 C 0 3 to 0.5 %. 
After 23 hours in the incubator, the fibrin had disappeared in Nos. 1 and 3, and 
was attacked in No. 2 : the tryptophane-reactions were, strong in No. 1, distinct 
in No. 2, marked in No. 3 : 28 hours later the fibrin had disappeared also in No. 2. 
Experiment 2. Similar extracts were prepared of the tulip and onion bulbs : 
40 cc. of the extract were in each case put, with 0-2 grm. fibrin, into each of 4 bottles, 
with the following additions: to No. 1, nothing; to No. 2, HC 1 to 0-05 % ; to No. 3, 
HC 1 to 0*2 % ; to No. 4, Na 2 C 0 3 to 1 %. 
Within 48 hours the results were : tulip, fibrin gone in No. 1 ; nearly gone 
in Nos. 2 and 4 ; unaltered in No. 3 : onion, fibrin unaltered in all. All the bottles 
gave more or less strong tryptophane-reaction. 
The positive results given by the hyacinth and the tulip point to the 
probability that a peptonizing enzyme is more generally present in plants 
than is at present recognized. But the negative result given by the onion 
is even more suggestive ; clearly peptolysis (autolysis) had occurred in this 
experiment without peptonization of the added fibrin. It appears, there- 
fore, that erepsin is present in the onion without any other protease. 
If this be so, it is important evidence in favour of the existence of an 
ereptic protease in plants, and strengthens the conclusion, already expressed, 
that in those plants that can digest fibrin there is also present a distinct 
peptonizing enzyme. 
