194 VEGETABLE PHYSIOLOGY 
bristles, and is closed bya sort of trapdoor which opens 
inwards and shuts again with a kind of spring. A small 
animal such ag an aquatic insect can easily open it by press- 
ing against it, and thus can enter the bladder. The trapdoor 
immediately closes by virtue of its own elasticity, and 
cannot be opened by pressure from within. The insect 
Fie. 92.—Traps or Utricularia neglecta. (Atter Kerner.) 
a, a bladder magnified (x 4); 6, section of a bladder; c, absorption-cells 
on the internal surface of the bladder ( x 250). 
accordingly finds egress impossible, and after a short time, 
usually ranging from one to three days, it perishes and its 
body decays, yielding to the plant the products of its decom- 
position, which are absorbed by particular cells growing 
from the internal wall of the bladder (fig. 92). 
Some of the so-called pitcher-plants show a somewhat 
similar mechanism and utilise corresponding organic sub- 
stances. The Sarracentas afford good examples. These 
