FROM THE RED SEA TO THE NILE 



253 



The underflow of the khor formed a supply of ground water 

 which was readily available to deeply-rooting plants with the re- 

 sult that a positivel}^ luxuriant effect was given in some cases; 

 among which was that of Cissus quadrangular is, which formed great 

 masses of angled stems and thick, waxy leaves over the adjoining 

 shrubs, while a parasite, Cistanche lutea (Orobanchaceae) was fas- 

 tened upon its roots. 



No stop was made in the valleys on the crest of the range, but 

 our car was attached to a freight train making long stops at places 



Fig. 7. Slope towards the Xile in the Red Sea province of Sudan. The 

 depression shows camel-grass, Leptadenia and Acacia albida. 



where undisturbed vegetation came to within a few feet of the line. 

 This enabled us to see that here the succulents were represented by 

 aloes and by the fleshy asclepiads mentioned above (Fig. 6). 



After winding about among the mountains for many miles, the 

 route started down the long, gentle drainage channels which finally 

 lead to the Nile; and the change in vegetation was like that in com- 

 ing through the San Gorgonio pass in southern California, where 



