194 



VEGETABLE PHYSIOLOGY 



bristles, and is closed by a sort of trapdoor which opens 

 inwards and shuts again with a kind of spring. A small 

 animal such as 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 



FIG. 92. TRAPS OF Utricularia neglecta. (After Keruer.) 



a, a bladder magnified ( X 4) ; b, 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 Sarracenias afford good examples. These 



