OF INSECTIVOROUS PLANTS 451 



the activity of an enzyme already present; or stimulation may 

 have produced the activation of a zymogen present in the liquor; or 

 it may have increased the secretion of protease by the glands of the 

 pitcher. 



In the presence of acid, liquor from stimulated pitchers digested cer- 

 tain substrates more rapidly than did liquor from non-stimulated pitchers; 

 this was especially true of edestan. 



The proteolytic enzyme of the pitcher liquor undoubtedly plays a 

 highly important role in the digestion of insects within the pitcher. 



Ill 



A Bacteriological Study of the Pitcher Liquor of Nepenthes 



By 

 Joseph S. Hepburn, Ph. D. and E. Quintard St. John, M. D. 



Since certain investigators (9-10) have attributed the digestive action 

 of the pitcher Hquor of Nepenthes to the activity of micro-organisms, it 

 has seemed desirable to study the bacterial content of the pitcher Hquor, 

 and the proteolytic power of its bacteria. 



Description of the Media 



Bacterial counts were obtained by sowing the pitcher liquor — un- 

 diluted, and in several successive dilutions — on plain nutrient agar, 

 incubating the plates at 37°C., and counting the colonies in the usual 

 manner. 



For the study of the proteolytic activity of the bacteria of the pitcher 

 liquor, certain protein media were used, following, to a large extent, the 

 directions of Crabill and Reed (24). The basis of thesfe media was a 

 stock solution which contained magnesium and ferrous sulphates, dipo- 

 tassium phosphate, and potassium chloride. For soUd media a stock 

 agar was prepared by addition of 2 percent, of agar to this solution. The 

 protein sohd media were obtained by addition of approximately 1 per- 

 cent, of one of the following proteins to the stock agar: — casein, egg 

 albumen, carmine fibrin, edestin, ricin (Jacoby), protein (prepared from 

 aleuronat). After these media had been steriUzed, the proteins were 

 present as suspended, insoluble particles. Whenever proteolytic bac- 

 teria were present in the pitcher liquor plated on such media, their 

 colonies gradually digested and dissolved the suspended particles over 

 which they grew. 



