120 



PLANTS WITH TRAPS AND PITFALLS TO ENSNARE ANIMALS. 



neither provided with pitfalls nor capable of performing special movements, but 

 have leaves converted into lime-twigs and on them animals stick and are also 

 digested. 



The first and most extensive group included in the first section is that of 

 Utriculariae or Bladderworts. Their capturing apparatus consists of little bladders 

 with orifices closed in each case by a valve, which permits objects to penetrate into 



Fig. 17. — Bladderworts. 

 In the foreground Utncutana Grafiana; in the background Utricular ia viinor. 



the cavity of the bladder, but not to issue out of it. The Utricularise are rootless 

 plants which live suspended in water, and, according to the season of the year, 

 either sink down to the bottom or ascend to just below the surface. Upon the 

 approach of winter, when animal life is gradually disappearing in the chilled and 

 freezing upper layers of water, the leaves at the extremities of the floating stems 

 are enlarged and form spherical winter buds; the older parts of the stems together 

 with the leaves die, their cavities hitherto occupied by air are filled with water, and 

 they sink to the bottom drawing down with them the winter buds. After the 

 winter these buds elongate, detach themselves from the old stems and ascend near 

 the surface, where innumerable little aquatic animals are swimming to and fro, and 

 there develop two rows of lateral branches in rapid succession. Either all of these 

 are thickly covered with leaves which are divided into thread-like, repeatedly 



