146 Introduction to Botany. 



free edge swings against, and overlaps on the inside, the 

 thickened lower border of the opening (see Fig. 73, B}. 

 Stiff hairs fringe the opening on the outside, and probably 

 offer a place of refuge for small water crustaceans and 

 various small larvae when pursued by larger animals. The 

 little animals are apt to push their way farther into the 

 bladder, the door of which easily rises to admit them, but 

 never swings outward to permit their escape. Finally they 

 die, become disintegrated by bacteria inhabiting the in- 

 terior of the bladders, and the soluble products of their 

 decomposition are absorbed by the inner surface of the 

 bladder, and thence distributed to the rest of the plant. 

 Experiments seem to show that the animal food thus ob- 

 tained is useful in the nutrition of the bladderwort. 



