438 The Physiology of Plants BOOK in 



animal matter resulting from the putrefaction of its prey. 

 No enzyme appears to be secreted. 



Of the plants which capture insects by active movement 

 the most familiar is Drosera, several species of which were 

 very carefully studied. The first important researches 

 which were carried out upon these plants were those of 

 Nitschke, made in 1860 ; they included a complete in- 

 vestigation of their structure and habits. With the excep- 

 tion of Scott's discovery in 1862, that irritation of the 

 leaf-tentacles causes them to become inflected over the leaf, 

 little more was ascertained about them till after 1870, when 

 they excited great interest. Three species of Drosera 

 were examined very carefully in 1873 by Mrs. Treat of 

 New Jersey. The minute structure of the tentacles 

 was studied in 1873 by Warming, but the classical 

 researches which revealed the nature of the processes by 

 which they capture and digest their insect visitors were 

 those of Charles Darwin, whose great work upon the whole 

 group of insectivorous plants was published in 1875. In 

 this book, for the first time, was revealed the story of the 

 mechanism of digestion, carried out in a manner recalling 

 the process of proteolysis in animals, as well as the curious 

 accessory mechanism of stimulus and response, to which 

 attention will be directed in a subsequent chapter. Dar- 

 win's researches included a study of the histological changes 

 accompanying the secretion of the digestive fluid, and drew 

 attention to the curious changes in the cells, to which he 

 gave the name of aggregation, showing thereby that the 

 whole process involves special protoplasmic activity. Dar- 

 win's explanation of these protoplasmic changes was sub- 

 sequently modified by Cohn (1876), Pfeffer (1877), Schimper 

 (1882), Gardiner (1885), and De Vries (1886). The inti- 

 mate association of the cytoplasm and the nucleus in the 

 nutrition of the cells, accompanying and following absorp- 

 tion was the subject of important memoirs by Miss Huie 



