34 THE STBUGGLE FOE EIISTENCB. 



nues in leaf, the greater is the chance of its being able to push out 

 its immediate neighbours and of thus surviving. 



In every respect in which the character of the soil influences 

 the relative growth of different species, this influence increases in 

 geometrical ratio with the extent to which any one or more of the 

 qualities of the soil in question departs from the average type. 



III. Death, disease, unhealthy state, ob bbtabdation of 



GEOWTH, BBOUGHT ON BY CAUSES EXTBANEOUS TO THE FOEBST, 



vie. — 



(a.) Attacks of insects and other animals. — The remarks made 

 under this head for the first two Cases are equally applicable here. 

 Besides this, we know that many insect pests are characteristic of, 

 and limited to, certain kinds of trees, while some others, although 

 they have a decided preference, for certain kinds, are still found on 

 other species when these latter are not abundant enough ; that 

 cattle and deer will greedily devour the foliage of some kinds 

 and leave others untouched ; and so forth. Thus, for instance, it is 

 not uncommon to see every teak leaf over large tracts of the Central 

 Provinces eaten up by a Noctuid caterpillar in the space of a few 

 days, while the foliage of the various companion species is entirely 

 free from the pest. Similarly, the foliage of sal is attacked and 

 more or less completely devoured over large areas by the larva of 

 a Tineid moth. Again, Cerambyx and Hepiahd borers often 

 attack young teak shoots, piercing the wood up to the pith, where 

 they lodge, and thus either kill the portion of the shoot above the 

 wound, or ■ f stop or retard its growth, or allow it to be easily 

 snapped off by the wind, In some of the forests in Saugor, in the 

 Centr&l-'PToyin.ces, joung Stephegi/ne parvifolia }ia,\e no chance of 

 getting up, as the tender annual shoots are devoured by deer as fast 

 as they come up. So in the Himalayas, Quercus incana, dilatata, 

 and semecarpifolia can never rise above a mere bush where grazing 

 and lopping for fodder are unrestricted. For many miles on both 

 banks of the Ganges near Hardwar Odina Wodier is kept back by 

 elephants, which eat the young wood ; and bamboo would suffer still 

 more from their depredations, were it not for its production of new 

 culms every year. In some places in the outer Himalayas near the 

 Ganges, where sal is not abundant, that species is rapidly losing 

 ground owing to numerous individuals of it being knocked down by 

 elephants, which eat its bark medicinally. 



As regards cattle generally, there are some plants for the leaves 

 and young twigs of which they skow a strong partiaUty, so that 

 when these are abundant they will seldom take even a single bite 



