OF INSECTIVOROUS PLANTS 457 



micro-organisms of the colon-aerogenes group were present in 1 cc. of 

 the pitcher liquor examined. 



General Summary 



The following conclusions are based on the bacteriological experi- 

 ments. 



The liquor taken aseptically from unopened pitchers was found to be 

 sterile. 



The liquor in partly opened pitchers, which were free from insects, 

 contained a goodly number of bacteria. 



Liquor from open, active pitchers, containing insect remains, had a 

 bacterial count of from 48,000 to 8,000,000 per cc. These organisms 

 were rods (Bacteriaceae). The bacteria in the liquor from such pitchers 

 liquefied gelatin, and grew on agar in which the sole source of nitrogen 

 and carbon was either a protein (casein, egg albumen, carmine fibrin, 

 edestin, Jacoby's ricin, protein from aleuronat), or a simple organic 

 compound of nitrogen (glycocoll, acetamide, asparagin, ammonium 

 lactate). The bacteria usually digested the protein in the medium, but 

 the rate of digestion was exceedingly slow. The bacteria decomposed 

 the simple organic compounds of nitrogen; an odor recalling that of 

 ammonia and amines was frequently produced; the medium became al- 

 kaline in reaction; later on, this reaction changed to acid, but the bac- 

 terial colonies themselves remained alkaline. These bacteria did not 

 Hberate tryptophane nor produce indol in their action upon protein (from 

 aleuronat). The pitcher liquor, on the average, contained at least 

 10,000 micro-organisms of the colon-aerogenes group per cc. 



The following conclusions are supported by the results of our studies 

 on the protease and the bacteria of the pitcher Hquor. 



The slowness, with which bacterial digestion of the protein occurred, 

 shows that bacteria play but a secondary role in the digestion of the 

 insects in the pitcher. The leading role in the digestion is played by the 

 protease of the pitcher liquor. 



The bacteria live in symbiosis with the Nepenthes plant, drawing 

 their nutrition from the digested insects, and assisting somewhat in the 

 digestion of the insects. 



Needless to remark, the tissue enzymes of the insects may produce 

 autolysis of their tissues, and thereby assist in the digestion. 



