166 



The Plant World. 



Marloth does not call the Kaffir and Karroo regions desert, 

 and even apologizes for calling the still more pronouncedlv arid 

 Kalahari a desert by saying that it is not such in the same sense 

 as the Sahara. The Karroo has an annual rainfall of about 10 

 inches, and while by no means devoid of vegetation it possesses 

 markedly xerophilous types only, both of the sclerophyllous and 

 succulent types, and has an open stand of vegetation, so as to 

 fall well within the definition of desert. In the Kalahari the 

 rainfall is sometimes as much as 4 inches a year, often there is 

 no fall for several years. The only vegetation is scattered 

 clumps of Aristida, which grows when it may. On the sandv 

 soils in the Kalahari there are often closer stands of grass, and 

 on rock outcrops there are succulents. 



The western coastal region from Olifants River northward 

 is almost totally devoid of rainfall, and has sandy or rocky soil. 

 The vegetation is extremely scant and made up only of deep- 

 rooted forms of a most pronouncedlv sclerophyllous character, 

 including A canthosicyos horrida, Parkinsonia africana, Wel- 

 wUschia mirabilis and several Amaranthaceae. Compositae and 

 Gramineae. Succulent desert forms are absent from this region. 



Considerable space is given in the opening pages to an ac- 

 count of the climatic elements. Inasmuch as the Cape lies in 

 nearly the same latitude as the United States it is of interest to 

 note that the major plant formations, forest, grass steppe, suc- 

 culent desert and sclerophyllous desert, are determined in their 

 distribution by the same features of amount and seasonal dis- 

 tribution of rainfall in both countries. Throughout his treatment 

 Marloth gives attention to the influence of soil conditions in 

 causing the occurrence of plant formations different from those 

 of the locality in which they lie, describing islands of Karroo 

 vegetation in the Cape region and the occurrence of the Cape 

 vegetation on particular soils at the interior. The anatomical 

 and other notes touch on a diversity of subjects such as leaf 

 structure, the character of the storage tissues of succulents, the 

 underground storage organs of herbaceous perennials, the ab- 

 sorption of water by aerial parts, and the longevity of desert 

 plants. 



