CHAP, ix Nutrition of Heterotrophic Plants 437 



carnivorous or insectivorous plants between 1860 and 1900 

 very considerably extended our knowledge of their modes 

 of life, and the number of species known to possess the power 

 of appropriating animal food was increased. The researches 

 were directed mainly to Nepenthes of the pitcher plants, 

 and to Drosera and Dionaea among those which effect 

 capture by means of movement. 



Little accurate information about the pitcher plants had 

 been obtained prior to 1874, when a comprehensive account 

 of what was known about them was given by Hooker in an 

 address to the British Association at Belfast. Besides 

 describing the arrangements of the pitchers for catching 

 flies, as shown in Sarracenia, Nepenthes, and Darlingtonia, 

 he showed that the liquid in the pitcher of Nepenthes is 

 possessed of digestive power, which is associated with 

 a pepsin-like secretion of its inner wall. About the same 

 time Mellichamp showed that the liquid which the pitchers 

 of Sarracenia contain is not collected from rain, but is 

 exuded from the cells of the pitcher wall. 



Von Gorup-Besanez and Will, in 1876, made a detailed 

 study of the action of the secretion of Nepenthes on fibrin 

 and found it able to decompose the latter and to produce 

 peptone. They gave attention also to the conditions under 

 which the digestive power appears, and showed it to be 

 due to an enzyme, working in an acid medium. In 1877 

 Vines extracted the enzyme by glycerin from the wall of 

 the pitchers, and proved that in unstimulated pitchers it 

 exists as a zymogen in the cells of the glands the walls con- 

 tain. In 1890 Dubois denied the existence of the enzyme, 

 attributing the digestive action to bacteria. Tischutkin 

 supported him in 1891. Vines, in further researches in 

 1897, showed conclusively that the enzyme is secreted, and 

 carried his discovery further by proving it to be one of 

 the tryptic group. 



Sarracenia was shown in 1882 by Schimper to absorb 



