OF FOREST SOILS, &('., IN INDIA. 101 



the soil of deciduous grass forests becomes mixed with the 

 fine particles of charred grass, which sometimes lie to the 

 depth of an inch or so on the surface after a forest fire. 

 These are swallowed with atoms of earth and grass by earth- 

 worms, and thus thoroughly mixed with the soil, which in 

 this manner obtains its dark colour. 



In the heavy evergreen tropical forests, on the other hand, 

 forest fires never (or very seldom) enter. The legions of 

 earthworms that inhabit the soils of such forests devour 

 and throw up to the surface almost pure vegetable humus, 

 and this operation being continually carried on for ages, 

 gradually covers stones, and gravel often to a great depth, 

 with a rich and finely comminuted vegetable soil. 



We are little aware what important services are being 

 rendered to us by such despised insects as white ants, 

 and earthworms ; were it not for the former, all vegetable 

 substances would be burnt up in deciduous forests and 

 wasted, and the soil gradually but surely impoverished; 

 and were it not for the latter, the substances buried by the 

 former would not be returned to the surface of the soil, and 

 thus brought within reach of surface rooting plants, nor 

 would soils barren and gravelly or stoney on the surface 

 be coated with a rich mould which the tender radicles of 

 the fallen seeds of forest trees find no difficulty in pene- 

 trating and absorbing food from. 



Not only do white ants improve the soil by burying 

 vegetable substances in it, but by continually carrying to the 

 surface the finer particles of the soil from great depths, 

 both for the construction of their tumuli and for purposes of 

 protection from their enemies, for they coat everything they 

 attack with a thin layer of fine earth, before gnawing it 

 away, they perform for us some of the services of the earth- 

 worm in burying gravel and stones. 



Not only are forests affected by these two great classes 

 of insects, but pasturages are improved by the earthworm, 

 which annually coats the surface of the soil, in some places, 

 to a depth of nearly two inches, with its castings. 



