CHAPTEK XXXI 

 HOW PLANTS PROTECT THEMSELVES FROM ANIMALS 



384. Destruction by animals All animals are supported 

 directly or indirectly by plants. In some cases the animal 

 secures its food without much damage to the plant on which it 

 feeds. Browsing on the lower branches of a tree may do it little 

 injury, and grazing animals, if not numerous, may not seriously 

 harm the pasture in which they feed. Fruit-eating animals 

 may even be of much service by dispersing seeds (Sec. 420). 

 But seed-eating birds and quadrupeds, animals which (like the 

 hog) dig up fleshy roots, rootstocks, tubers, or bulbs, and eat 

 them, or animals which (like the sheep) graze so closely as to 

 expose the roots of grasses or even of forest trees to be parched 

 by the sun, destroy immense numbers of plants. Many trees, 

 as the apple, peach, and black locust, have the trunk fatally 

 weakened by the boring larvae of insects. Leaf-eating insects, 

 such as grasshoppers and caterpillars, cause immense damage 

 to foliage, and others, like the chinch bug so destructive to 

 grain crops, suck the juices from roots, stems, or leaves. 



385. Some modes of protection from animals. Many of the 

 characteristics of plants may be wholly or partly due to adapta- 

 tions for protective purposes, while in particular cases we cannot 

 be sure of the fact. Perching on lofty rocks or on branches of 

 trees, burying the perennial part (bulb, rootstock, etc.) under- 

 ground, growing in dense masses, like a canebrake or a thicket 

 of blackberry bushes, all such habits of plants may be partly 

 or altogether valuable to the plant as means of avoiding the 

 attacks of animals, but this cannot be proved. On the other 

 hand, there are plenty of instances of structures, habits, or accu- 

 mulations of stored material in their tissue which plants seem 



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