CH. 



SOIL 



on cotton soil, while Fig. 2, which represents forest on 

 limey soil, shows a mixed crop which is made up of 

 Anogeissus leiocarpus, Stereospermum Kunthianum, 

 Dalbergia Melanoxylon, and several others (not seen 

 in the photograph), such as Sterculia cinerea, Loncho- 

 carpus laxijiorus, Adansonia digitata, etc. The 

 difference of effect of soil on vegetation is so marked 



Fig. 1. Pure forest of Acacia Seyal on cotton soil, Sudan. 



that, even where small masses of the limey soil occur 

 in the midst of the vast extent of cotton soil, the 

 vegetation at once changes, and the Acacia gives way 

 to the other species which favour a limey soil. 



Sandy soils consist mostly, that is 75 per cent or 

 more, of silica in the shape of disintegrated sand. 

 They are soils which get hot quickly and cool quickly. 

 They absorb water greedily, but they also give it up 



