THE PHYSIOLOGY OF NUTRITION 



decomposing the dead bodies, and thus the plant is able to 

 obtain a portion of the nitrogen which it requires. 



In many parts of the ditches, ponds, or pools in Scotland and 

 Ireland an aquatic carnivorous plant is found. Growing from it 

 are a large number of small bladders which vary in size from one- 

 eighth to one-quarter of an inch in diameter. It receives the name 

 of the Bladderwort (Fig. 152). Each bladder is full of water. 



FIG. 152. Bladderwort. 



FIG. 153. A, bladder of Bladderwort ; B, sec- 

 tion of bladder ; C, wall of bladder, more 

 highly magnified. 



Entrance into the bladder is effected through the opening at 

 one end. The opening is guarded by a valve which is a sort, of 

 a trap-door opening inwards and sloping towards the cavity. 

 The valve is guarded internally by a number of stiff hairs, 

 and the external opening is protected from large animals by 

 long multicellular hairs. The bladder (Fig. 153) is lined 

 with a number of cells which can absorb materials from the 

 bladder. 



The whole of the apparatus is a trap for small aquatic animals. 

 They can enter but never return. The animal pushes against 



K 2 



