Cn. IVJ WARM TEMPERATE MOIST SUMMER DISTRICTS 499 



share in the differentiation and distribution of individual forms may be 

 assigned to the numerous herbivorous and seed-devouring mammals and 

 birds, to the pollinating insects or active small animals of all kinds — all this 

 still requires investigation. In most cases no observations made on the spot 

 are available, but our knowledge of the natural history of the grassland is 

 essentially limited to herbarium specimens and data based on them. 



Fig. 263. Prosopis juliflora, DC, the mezquit. Texas, on the lower Rio Grande. 

 From a photograph by C. G. Pringle, lent by Prof. Sargent. 



ii. GRASSLAND IN SOUTH AFRICA. 

 Thode * gives the following striking description of the savannah in British 

 Kaffraria : — 



' The months of May to July form the driest season of the year, and are therefore 

 poorest in flowers 2 : the sky is vaulted cloudlessly over the dry wintry landscape ; 

 the pure dry air, clear and transparent, allows the outlines of distant objects and 

 the deep blue of the ocean to stand out sharply. At this time the extensive tracts 

 of grass present a uniformly faded appearance, the deciduous shrubs and trees lose 



1 Thode, op. cit., I, p. 597. 2 This conclusion is incorrect. 



K k 2 



