OF INSECTIVOROUS PLANTS 429 



filter of a true proteolytic enz>Tne, and not to the retention of proteolytic 

 bacteria, i.e., the liquor owed its proteolytic power to a true enzyme. 



Experiments (usually, though not invariably, made on washed, un- 

 opened pitchers) showed that "under certain circumstances, previous 

 treament with acid causes the glands of the pitcher to yield a more active 

 glycerin-extract, or to yield an active extract when otherwise the extract 

 would be inactive; and it can only be concluded that this must be due to 

 the presence of a zymogen in the glands from which the enzyme is lib- 

 erated on treatment with acid. " The zymogen was best converted into 

 active enzyme by treatment of the glandular tissue with acid for a short 

 time at a relatively high temperature, say ^4 hour at 50° C. Action of 

 the acid for a longer time at lower temperature, not only activated the 

 enzyme but also extracted it from the glands. In the activation experi- 

 ments, 0.25 percent hydrochloric acid was used; 0.5 percent acetic acid 

 apparently was less satisfactory. One function of the high acidity of 

 the liquor in unopened pitchers probably is to activate the zymogen. 



Peptone and leucine were recognized among the products of digestion. 



Vines concludes that the enz\Tne is derived from a zymogen which is 

 present in the gland cells. The enzyme is a tryptic ferment, requires an 

 acid medium for its action, and resembles the proteases of germinating 

 seeds with respect to the reaction of the medium, which it requires, and 

 the products, which it forms. 



In his final paper on the proteolytic enzyme of Nepenthes, Vines (8) 

 appHes to it the name "Nepenthin." Fibrin and Witte peptone were 

 subjected to a somewhat prolonged digestion at 38.5° C. with pitcher 

 Uquor, to which hydrochloric or citric acid had been added. The follow- 

 ing are typical experiments: — 



I. 10 grams moist fibrin 



50 cc. 0.3% hydrochloric acid 

 50 cc. pitcher liquor (from N. Mastersiana) 

 Period of incubation I8I/2 hours 

 II. 1 gram Witte peptone 

 0.2 gram citric acid 

 10 cc. distilled water 

 40 cc. pitcher liquor 

 Period of incubation — from noon until morning of the next day. 



After digestion, the resulting solutions gave the tryptophane reaction 

 (a violet or pink color with chlorine water), which is stated to be charac- 

 teristic of tryptic digestion only. 



