Vines. — Proteolytic Enzymes in Plants (//). 615 
The action of the juice upon fibrin was then investigated. 
Inasmuch as in the previous experiment the activity of the 
juice had been found to be greatest in the bottle to which no 
acid had been added, no acid was added in this case : but the 
contents of the bottles were very distinctly acid at the close 
of the experiment. The result indicates that the juice does 
not act upon fibrin. 
40 cc. of expressed juice, diluted with an equal vol. of dist. water, 
were placed in each of 3 bottles, with some thymol: to (1) nothing 
further was added; to (2) 0-5 grm. of Witte-peptone ; to (3) 1 grm. 
of moist fibrin. 
After 29 hours’ digestion at 40° C., (1) and (3) gave distinct 
tryptophane-reaction, (2) a strong reaction. The fibrin in (3) did not 
appear to have been attacked to any extent, so that the tryptophane- 
reaction was due to autolysis. 
Inasmuch as neither the enzyme of the Sea-kale, nor that 
of the Dahlia acts upon fibrin, they are to be referred, like 
those of many other plants (see my previous paper, 1), to the 
erepsin-group of proteases. 
Betula alba. 
I happened to have the opportunity of investigating the sap 
poured out by a ‘ bleeding 5 Birch-tree. 
The sap is a clear, yellowish, neutral liquid : it gives the 
peroxidase- but not the oxidase-reaction with guaiacum, also 
faint xanthoproteic and Millon’s reaction, no tryptophane or 
biuret-reaction, but strong sugar-reaction with Fehling’s 
solution. 
Digestion-experiments were made with and without added 
proteid (Witte-peptone and fibrin), the sap being acidified 
with citric acid or made alkaline with Na 2 C 0 3 , also with or 
without the addition of a few drops of HCN solution as an 
antiseptic, but in no case was any tryptophane-reaction 
observed, even when digestion was prolonged to forty-eight 
hours. The sap apparently contains no protease. 
