206 



AFRICA 



of a cushion plant, the anabasis, also called ' desert 

 cauliflower'. Such tussocks are made up of packed 

 bundles of wiry shoots bristling with leathery, short, 

 pointed and crowded leaves, and glued fast together by 

 the dried clay. But for a few distant leafless bushes 

 of zollikoferia and ephedra, two feet high, the ground 

 seems bare as far as the horizon : on looking carefully, 

 however, one discovers a large variety of pigmy plants. 



FIG. 78. Reg Desert Sinai. 1 



Where the gravel and clay are ground to impalpable 

 drifting sands, the formations of sand-dunes or 'erg' 

 arise. Vast tracts of this sea of moving sand may 

 remain entirely plantless: nothing seems to vary the 

 beauty of the vivid orange billows ; but, at other places 

 and more frequently, the surface is sprinkled with spots 



1 Reproduced from a photograph of the Ordnance Survey by per- 

 mission of the Controller of H.M. Stationery Office. 



