344 FOUNDATIONS OF BOTANY 



Fig. 241, terminate in a hinged portion which is surrounded 

 by a fringe of stiff bristles. On the inside of each half 

 of the trap grow three short hairs. The trap is so sensi- 

 tive that when these hairs are touched it closes with a jerk 

 and very generally succeeds in capturing the fly or other 

 insect which has sprung it. The imprisoned insect then 

 dies and is digested, somewhat as in the case of those 

 caught by the sundew, after which the trap reopens and 

 is ready for fresh captures. 



411. Object of catching Animal Food. It is easy to 

 understand why a good many kinds of plants have taken 

 to catching insects and absorbing the digested products. 

 Carnivorous, or flesh-eating, plants belong usually to one 

 of two classes as regards their place of growth ; they are 

 bog-plants or air-plants. In either case their roots find it 

 difficult to secure much nitrogen-containing food, that is, 

 much food out of which proteid material can be built up. 

 Animal food, being itself largely proteid, is admirably 

 adapted to nourish the growing parts of plants, and those 

 which could develop insect-catching powers would stand 

 a far better chance to exist as air-plants or in the thin, 

 watery soil of bogs than plants which had acquired no 

 such resources. 



