14 THE STRUGGLE FOB EXISTENCE. 



the victory all the more easily to the latter, since these will have 

 numerous lateral roots traversing the soil in every direction and 

 drawing nourishment from an extended area. In this respect 

 suckers will be the best of of all, for they will necessarily obtain a 

 part of their nourishment from their parent-root, the tree producing 

 which may be situated a certain distance off, where the conditions 

 of soil and subsoil are better. Moreover suckers have another ad- 

 vantage over stool-shoots in that they stand singly on their parent 

 roots, instead of forming a clump and having to share the reserve 

 materials with their sister shoots. 



When the crop is old enough for the component stems to stand 

 far apart, then, of course, variations in the soil and subsoil will 

 always exercise a powerful influence on the struggle for existence. 



III. DEATH, DISEASE, UNHEALTHY STATE, OR RETARDATION OF 



GROWTH DUE TO CAUSES EXTRANEOUS TO THE FOREST, VIZ : 



(a) Attacks of insects and other animals. Some insects, especi- 

 ally the lignivorous kinds, attack c Mefly or solely the weaker 

 plants, particularly those that have already begun to decay, while 

 others, like certain caterpillars, notably the various silkworms, 

 and the larvse of saw-flies and gall-flies and of certain Coleoptera, 

 attack all indifferently, and even rather affect plants possessing 

 abundant well-developed succulent twigs and foliage. Again, the 

 lac insect prefers the strong juicy shoots of vigorous plants to 

 the more or less dry, more or less hide-bound twigs of less vigor- 

 ous individuals. Insects which attack the roots of plants wall 

 usually exercise no choice as between the strong and the weak, 

 but mere accident might lead to their killing or keeping back the 

 stronger individuals and enabling the weaker to survive. Cattle 

 and deer, in rubbing their bodies or their horns against trees, often 

 peel off the bark and thus throw them back. During the rains 

 buffaloes, to escape from flies, bury their heads in thick masses of 

 foliage and, in agitating their heads, wrench and break off branches 

 and even stems with their long horns. Elephants not unfrequently 

 knock down trees and thus uncover overtopped plants or give 

 lateral room for development to trees which had been pressed in 

 before. Monkeys not only eat leaves and juicy twigs, but break off 

 much more than they can eat, and in jumping from branch to 

 branch do great damage, especially when the species forming 

 the crop replaces a broken leader with difficulty. Cattle, goats, 

 and other ruminants while they do not spare weakly plants, still 

 fall more greedily on strong ones possessing abundant, well-deve- 



