ANIMALS AS FOOD, FOES, OR FRIENDS. 347 



trap. The blade is two-lobed, with a hinge along the middle 

 (figs. 205, 388). The hinge is in reality a cushion of tissue 

 upon the back, which quickly throws the two halves of the 

 leaf together when the sensitive hairs on the inner face 

 of the trap are touched. The movement is sudden enough 

 in Dioncea to catch the slow-flying insect, or, in Aldrovandia t 

 the minute water animal. The prey is prevented from escap- 

 ing by the interlocking, tooth-like lobes along the edges 

 of the leaf. Digestion and absorption of the nitrogenous 

 materials follow.* 



II. Herbivorous animals. 



470. Protection. — While a really insignificant number of 

 minute animals are eaten by plants, a very large number of 

 plants find it necessary to protect themselves in some way 

 against destruction by browsing animals, insects, snails, 

 and slugs. Since the animal world relies for its food 

 supply ultimately upon the green plants, it is plain that 

 no such protective measures are completely effective. The 

 protection, therefore, may be looked upon as a protection 

 against extermination rather than against injury. As pro- 

 tective adaptations against browsing animals are usually 

 reckoned : 



471. 1. Armor, in the form of hard, leathery, sharp- 

 edged, woolly, bristly, or sticky parts, especially leaves 

 (figs. 361, 362, 364, 389); or thorns (figs. 157, 390), prickles 

 (fig. 115), or stinging hairs (fig. 391). 



* Travesties upon these strange methods of nutrition appear periodically 

 in newspapers, and plants of remarkable size and forbidding aspect are 

 represented as capturing birds, animals, and even men, that venture into 

 their neighborhood. It should be noted, therefore, that in all cases the 

 plants which capture animal food entrap only the smaller animals, scarcely 

 any of them, except those caught by the pitcher plants, larger than the 

 common house-fly. 



