434 HEPBURN— BIOCHEMICAL STUDIES 



may occur even in otherwise normal pitchers; it is probable, but not 

 certain, that an increased secretion of enzyme occurs in the opened 

 pitchers in the presence of stimulating substances." However, an in- 

 creased secretion could not be detected in a pitcher stimulated by a 

 fibrin flock, and compared with an unstimulated pitcher as a control; 

 but one such experiment was made. 



The tests for a protease in the glands of the pitcher-cover, which 

 secrete nectar, were entirely negative. Flocks of fibrin were fastened 

 over the glands by means of filter paper, which was kept moist. Diges- 

 tion of the fibrin did not occur. 



The glycerol extract of the pitchers contained too little enzyme and 

 showed no proteolytic activity. Apparently the procedure of Vines (5) 

 for the detection of enzymic activity was followed. 



The secretion of unopened pitchers of Nepenthes paradisiaca was 

 neutral in reaction. The hquor of unopened pitchers of Nepenthes 

 M aster siana was strongly acid; when fibrin was introduced into these 

 pitchers, it was dissolved in 3 days, and cubes of albumen were strongly 

 attacked; the protein was peptonized in the pitcher, and no bacteria 

 were present. 



A pitcher of Nepenthes Sedeni contained a strongly acid liquor and 

 dissolved fibrin in 25 hours. Similar observations were made with a 

 pitcher of Nepenthes robusta. Cultures demonstrated the absence of 

 bacteria. The filtered solutions from the pitchers plus 0.1 percent 

 formic acid digested meat fibres in 5 hours at a temperature of 35° C. 



Goebel states that free formic acid could be shown to be present in 

 the secretion (pitcher hquor) of the species of Nepenthes studied by him- 

 self. The total acidity of diff'erent pitchers, calculated as formic acid, 

 was:— 0.036%, 0.025%, 0.021%. All bacteria are not killed by this 

 degree of acidity. 



The strongly acid pitcher-Hquor of Nepenthes Mastersiana was sown 

 on non-acid nutrient gelatin, and on nutrient gelatin rendered acid by 

 the addition of 0.2 percent tartaric acid. After 8 or 9 days, no growth 

 was noted, or else a few bacteria and molds, which were doubtless due 

 to air-contamination. 



Goebel considered that a true enz\Tnic digestion occurred in normal 

 pitchers of Nepenthes, in which the Hquor had not been diluted by water; 

 this dilution often occurs in greenhouses. The enzjnne was classified as 

 a peptonizing enz\Tne, not identical with pepsin, and different from the 

 pancreatic protease. Bacterial digestion could occur only in the liquor 



