Environment and Adaptation 219 



Carnivorous Plants. A most extraordinary form 

 of adaptation is that of the so-called carnivorous 

 plants, of which a number of remarkable types are 

 common in the United States. These are either 

 aquatics or bog plants, and it is supposed that their 

 peculiar habits are due to a deficiency of nitrogen 

 in their environment. In the sundew (Drosera), 

 butterwort (Pinguicula), and Venus's flytrap (Di- 

 onaea) the leaves are modified into traps, which 

 capture small insects alighting upon them, and after 

 the insect is secured, there is an actual digestion by 

 the aid of digestive ferments not unlike those found 

 in the digestive organs of animals. A similar fer- 

 ment has been demonstrated in the pitchers of the 

 Asiatic pitcher-plant (Nepenthes). In the Amer- 

 ican pitcher-plants (Sarracenia and Darlingtonia), 

 and in the bladder- weed (Utricularia), the leaves 

 form traps into which the insects are lured, but 

 there is very little or no digestive effect upon the 

 bodies of the victims, which are drowned and the 

 products of their decomposition are absorbed by the 

 leaf. These carnivorous, or insectivorous, plants are 

 among the most extraordinary examples of special 

 adaptation that are met with in the whole vegetable 

 kingdom. 



PLANTS AND ANIMALS 



As plants are essential to the existence of all ani- 

 mal life, it is not remarkable that the structures of 



