63° 



ZONES AND REGIONS [Pt. Ill, Sect. II 



The vegetation of the Karroo semi-desert, which is at an altitude of 

 1,800-2,000 feet in Cape Colony, is somewhat less meagre and exhibits 

 a richer systematic composition. The banks of mostly dry river beds, as in 

 the northern parts of the littoral deserts, are bordered by acacia-bushes 

 (Acacia horrida) ; all sorts of shrubs and bushes spring up from the soil, 

 which is almost bare during the dry season, but from which the verdant 

 and flowering shoots of numerous tuberous and bulbous plants (Pelargonium 

 sect. Hoarea (Fig. 362), Harpagophytum (Fig. 368), Liliaceae, Iridaceae, 

 Amaryllidaceae), sprout forth with the spring rains, if the latter be suffi- 





Fig. 365. Flora of the South-west African 

 desert: HereroLand. SarcocaulonMarlothi, 

 Engl. Natural size. After Engler. 



Fig. 366. Flora of the South- 

 west African desert. Sarco- 

 caulon sp. Resinous coating 

 of the stem. Two-thirds 

 natural size. 



ciently abundant, which, however, is not the case every year. The peren- 

 nial plants are chiefly succulents, such as species of Euphorbia, Stapelia, 

 Mesembryanthemum,Crassula, and the remarkable Sarcocaulon(Geraniaceae) 

 with a protective resinous coating (Figs. 365, 366) ; the remaining plants are 

 of an ericoid type, and frequently so similar in their vegetative organs that 

 only a close examination reveals their systematic heterogeneity, and shows 

 them to include representatives, for instance, of the Compositae, Polygala- 

 ceae, Leguminosae, Euphorbiaceae, Ficoideae, and Scrophulariaceae 1 . Very 



1 Scott-Elliot, op. cit. 



