HEPBURN— THE PITCHER LIQUOR OF NEPENTHES. 113 



present in the pitcher hquor. On the other hand, Dubois* and 

 Tischutkin^ conchided from their experiments that the digestion is 

 due to the activity of microorganisms. A third factor to be con- 

 sidered is the autolysis produced by the tissue enzymes of the cap- 

 tured insects. 



In the present research, the proteolytic enzyme of the pitcher 

 liquor and the bacteria, which occur in opened pitchers, have been 

 studied separately. The following species and hybrids of Nepen- 

 thes supplied material for the research : ampullaria, atrosangiiinia, 

 Chelsonii, Claytonii, Dommii, Dyeriana, gracilis, Hamiltoniana, Hen- 

 ryana, Hookeriana, Mastersiana, mixta, Morganiana, paradisee, 

 Rafflesiana pallida, rufescens, splendida, Wittei. The plants were 

 grown in the Nepenthes House of the University of Pennsylvania. 



Protease of the Pitcher Liquor. 



In the study of the protease of the pitcher liquor, pitchers were 

 always selected prior to opening. They were closely watched and 

 the mouth of each pitcher was closed with absorbent cotton as soon 

 as the lid opened ; the entrance of insects was thereby prevented, 

 and possible contamination of the pitcher liquor by the tissue en- 

 zymes of the digested prey was entirely excluded. The digestion 

 experiments with the pitcher liquor were made in vitro in the pres- 

 ence of a bactericide ; bacterial action was thereby excluded. The 

 proteolysis, which was observed, was, therefore, due to enzyme 

 action. 



Liquor from both non-stimulated and stimulated pitchers was 

 studied. The experiments on liquor from non-stimulated pitchers 

 were carried out as soon as possible after the opening of the pitchers. 



When liquor from stimulated pitchers was desired, recourse 

 was had to mechanical stimulation by chemically inert substances. 

 In some experiments, the glands of the inner wall of the pitcher 

 were stroked repeatedly with a camel's hair brush, and the cotton 

 plug was then inserted in the mouth of the pitcher; the liquor was 

 removed for study on the following day. In other experiments, 

 several round solid glass beads, such as are used in fractionating 



^Dubois, Comptes rend, dc I' Academic des Sciences, 1890, CXI., 315-317. 

 9 Tischutkin, Botanisches Centralblatt, 1892, L., 304-305. 



