Chap. V] TROPICAL DISTRICTS WITH DRY SEASONS 373 



Rhopala, that stand isolated here and there, and especially occur on eminences ; 

 these trees are never found in forests. The swampy depressions of the savannah 

 are for the most part occupied by Mauritia flexuosa, sometimes isolated, sometimes 

 forming actual forests.' 



The campos of Brazil, like the llanos and the savannahs of Guiana, 

 do not consist of a uniform formation spread over a wide area, but of 

 a richly differentiated, undulating park-like country, in which different 

 forms of woodland and grassland 

 partake, although the latter prepon- 

 derates. 



Saint-Hilaire also describes the 

 campos of Minas Geraes as a hilly 

 tract, the depressions in which form 

 true savannah with stuntedtrees, whilst 

 the heights are covered with pure 

 steppe. Yet the campo-district is by 

 no means without forest. ' Wherever 

 a damp and deep valley appears in 

 the midst of the free and merely un- 

 dulating surface of this immense dis- 

 trict, wherever a depression occurs 

 on the slope of a hill, one may be 

 certain of finding a group of trees ' '. 



The licrbaccous vegetation of the 

 savannah has most probably every- 

 where a xerophilous structure ; but 

 only a few observations of the vegeta- 

 tion of the campos, those of Warming, 

 are available. According to him, 

 many herbs, both Dicotyledones and 

 Monocotyledones, have tubers, which 

 function either primarily or secon- 

 darily as water-reservoirs (Figs. 203 

 and 204). The leaves of the grasses 

 are narrow and stiff, the leaves of 

 Dicotyledones are usually small and 

 hard, and frequently the plants are reduced to a completely aphyllous 

 condition. 



Warming has thoroughly studied the systematic composition of the campo of 

 Lagoa Santa in Minas Geraes (Figs. 201-205). He found 554 herbaceous species. 

 The majority of individual plants are grasses, of which about 60 species in particular 



1 Saint-Hilaire, op. cit., p. 9. 



Fig. 203. Vernonia desertorum. From the 

 Brazilian campos of Minas Geraes. Natural 

 size. After 'Warminq;. 



