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 
Utricularie 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 Utricularia Grafiana ; in the background Utricularia minor. 
the cavity of the bladder, but not to issue out of it. The Utriculariz 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 
