OF INSECTIVOROUS PLANTS 427 



filtrate digested fibrin, while a control experiment on fibrin plus 0.25 

 percent hydrochloric acid gave no digestion. After the precipitate had 

 been kept in a bottle with chloroform vapor for a month, the enzyme 

 contained in it was still active. 



Vines was unable to find a zv-mogen of the protease in the pitcher 

 liquor, although the activation of a z\Tnogen was suggested by the 

 requirement that acid be added in order to produce proteolysis. 



Glycerol extracts, prepared from the washed and dried tissue of 

 relatively young, vigorous pitchers, contained a protease which acted 

 in the presence of 0.25 percent hydrochloric acid, and retained its activity 

 for as long as 2 months, but not indefinitely. 



Vines concluded that the digestive action of the pitcher liquor is due 

 to an enzyme. He detected albumose, but not peptone, as a product of 

 the digestion, and suggests that peptone was formed and immediately 

 split into other compounds. Wheat gluten was digested in the same 

 manner as fibrin. 



Most of these experiments were made on N. mastersiana. The liquor 

 in the unopened pitchers of this species usually was distinctly acid. 



In his next paper on the proteolytic enzyme of Nepenthes, Vines (7) 

 studied the action of heat on the protease. The pitcher liquor was 

 heated, then cooled; acid and fibrin were added, and digestion was 

 carried out as in the previous study. Control experiments were made on 

 the unheated pitcher liquor. Heating the liquor at 80° C. for 15 to 20 

 minutes did not destroy the enzyme, but the proteolytic power was 

 decreased to a marked degree. Thus in one experiment the heated liquor 

 completely digested the fibrin in approximately 4 days, while the un- 

 heated liquor in the control experiment required but 3 hours to digest 

 the fibrin completely. WTien the liquor was held at 78° to 83° C. for 

 30 minutes, the enzyme was completely inactivated; no digestion occurred 

 in 4 days, while the control experiment on unheated liquor gave complete 

 digestion of the fibrin in Ij/^ hours. When the liquor was kept at 80° C. 

 for 30 minutes, the enzyme was completely inactivated, and exerted no 

 proteolytic action on fibrin after digestion for 1 week; the unheated 

 control completely digested the fibrin in 5 hours. Boiling the liquor 

 "for some seconds" partly inactivated but did not completely destroy 

 the enz>Tne. It was necessary to subject the liquor to a temperature of 

 100° C. "for an appreciable time, say 3-5 minutes," in order to destroy 

 the enzyme completely. 



The destructive action of sodium carbonate on the enzyme was also 

 studied. The degree of inactivation of the enzyme depended on the con- 



