CHAP. LXXX TRUE SAVANNAH 



297 



Lichens, mosses, and algae are entirely absent from the soil, and, at 

 the most, are scantily represented on stones and trees. 



The leaves of the dicotylous plants show xerophily, particularly in 

 their stiffness (for they are often so rigid and dry as to rattle in the wind), 

 in their lie, often in small size (though many are broad, oblong, or obovate, 

 or compound ; ericoid and pinoid types being almost unrepresented), 

 and in their very hairy nature or, if glabrous, in their waxy or lacquered 

 coatings. 



Ethereal oils are present in a whole series of the plants, and, in South 

 America, especially in Verbenaceae, Labiatae, and Myrtaceae. 



Many trees in tropical savannah are leafless during the dry season, 

 or shed their foliage during this period. Yet this is the time at which 

 many species are in flower. In this respect the Brazilian campos are not 

 typical, but rather form a transition towards subtropical savannah, as 

 the leafless season is very short. 1 This arises from the circumstance that 

 winter on the Brazilian upland is not so hot as in tropical lowlands, for 

 which reason there is less transpiration ; in addition the dry season in 

 the campos is not without a scanty supply of rain. 



The physiognomy of savannah is subject to great variety, which 

 depends partly upon the height of the vegetation and partly upon the 

 share taken on the one hand by grasses and perennial herbs, and on the 

 other by shrubs and trees. 



In Brazil and Venezuela there are some savannahs campos in which 

 trees, rising above ground that is clothed with vegetation varying from 

 half a metre to a metre in height, are so close together as to produce a kind 

 of forest, which is open, sunny, shadeless, and hot, and allows the pedes- 

 trian to walk freely and the horseman to ride in all directions : such are 

 the Brazilian campos serrados. There are other savannahs in which trees 

 are extremely scanty and low, or are entirely wanting, and the carpet 

 of grass and perennial herbs is very short and almost sward-like. In 

 Matto Grosso, in the interior of Brazil, according to Pilger 2 the dry 

 season is not entirely rainless. Most of the trees are deciduous and 

 blossom after defoliation. Along the streamlets there extends forest 

 composed of Mauritia vinifera and evergreen trees and shrubs, with 

 perennial herbs, sedges, and grasses carpeting the ground. 



Llanos. 



Belonging to a special type of savannah are the llanos, which form 

 boundless plains to Venezuela and have been so admirably described by 

 Humboldt. 3 In the llanos trees are very few in number ; indeed they 

 may be entirely wanting save in the moistest places, where palms, including 

 Mauritia flexuosa and a species of Corypha, together with other plants, 

 give rise to forest, which does not itself really belong to savannah ; in 

 other places isolated trees of the proteaceous Rhopala or other species 

 occur. Grasses form a vegetable covering, often as tall as man, and with 

 them are mingled Compositae, Leguminosae, Labiatae, and so forth. 

 Large portions of the llanos are under water during the rainy season, 



1 Warming, 1892. * Pilger, 1902. 



3 In addition to Humboldt's works, that of C. Sachs should be consulted. 



