164 



PLANT STUDIES 



This association of insects and flowers is sometimes so 

 intimate that they have come to depend absolutely upon 

 one another. Especially among the orchids is it true that 

 special flowers and insects are adapted so exactly to one 



another, that if one dis- 

 appears the other be- 

 comes extinct also. 



122. " Carnivorous '' 

 plants. — This name has 

 been given to plants 

 which have developed 

 the curious habit of 

 capturing insects and 

 using them for food, 

 and perhaps they had 

 better be called " insec- 

 tivorous plants." They 

 are green plants and, 

 therefore, can manu- 

 facture carbohydrates. 

 But they live in soil 

 poor in nitrogen com- 

 pounds, and hence pro- 

 teid formation is inter- 

 fered with. The bodies 

 of captured insects sup- 

 plement the proteid 

 supply, and the plants 

 have come to depend 

 upon them. Many, if 

 not all, of these car- 

 nivorous plants secrete 

 a digestive substance 

 which .acts upon the 

 bodies of the captured insects very much as the diges- 

 tive substances of the alimentary canal act upon proteids 



Fig. 154. The Californian pitcher plant (Dar- 

 lingtoniri), showing twisted and winged pitch- 

 er, the overarching hood with translucent 

 spots, and the fish-tail appendage to the hood 

 which is attractive to flying insects.— After 

 Kei'.nrr. 



