SUDAN SEMI-DESERT 



209 



a sufficiency of ground water, groves, woods, or even 

 extensive forests of doum-palm (kyphaene thebaica) are 

 the rule ; but the predominant features are the 

 acacia, of which there are many species, some of them 

 local, others of wide distribution, and the umbrella shape 

 of the thorny trees arranged in scattered woods. The 

 clayey soils, heavy and retentive, generally remain tree- 



Fig. 79. Semi-desert — Nigeria. 



less and give rise to marshes and even lagoons. Here 

 and there swards of pennisetum grass may be seen. 

 Some cultivation is now possible, the dhurra millet 

 being the commonest crop. 



Such are the general features of the belt of land, about 

 300 miles broad on an average, which stretches from the 

 Atlantic to the Red Sea on the margin of the desert It 



1159.1 



