342 



FOUNDATIONS OF BOTANY 



FIG. 239. Blade of Leaf 

 of Sundew. (Somewhat 

 magnified.) 



This growth completely surrounds the 

 young, active tips of all the roots and 

 the threads of the mykorhiza, as it is 

 called, seem to do the work of root- 

 hairs. 



410. Carnivorous Plants. In the 

 ordinary pitcher-plants (Fig. 237) the 

 leaf appears in the shape of a more or 

 less hooded pitcher. These pitchers 

 are usually partly filled with water, 

 and in this water very many drowned 

 and decaying insects are commonly 

 to be found. The insects have flown 

 or crawled into the pitcher, and, once inside, have been 

 unable to escape on account of the dense growth of bristly 

 hairs about the mouth, all pointing inward and downward. 

 How much the com- 

 mon American pitcher- 

 plants depend for 

 nourishment on the 

 drowned insects in the 

 pitchers is not defi- 

 nitely known, but it is 

 certain that some of 

 the tropical species re- 

 quire such food. 1 



FIG. 240. Leaves of Sundew. (Somewhat 



In other rather com- magnified.) 



mon plants, the SUn- The one at the left has all its tentacles closed 

 -. over captured prey ; the one at the right has 



6WS, insects are only half of them thus closed. 



1 Where the Sarracenia is abundant it will be found interesting and profit- 

 able to make a careful class study of its leaves. See Geddes, Chapters in 

 Modern Botany, Chapters I and II. 



