32 SOUTH AMERICA— THE ANDES REGIONS. 



rivers, the forest presents an unbroken surface in which human labour has 

 hitherto made but a few isolated clearings. They are scarcely even traversed by 

 any beaten tracks, except those made by the puma, tapir and peccary. Like the 

 ocean, like the snowfields of the polar regions, the verdant seas covering tropical 

 America seem to constitute a world apart, presenting an endless diversity of 

 sjoecies, but of remarkable uniformity in its general asj^ect. The trees interlace 

 their branches ; trunks and foliage are bound together by the coils of the lianas, 

 until the whole forms an inextricable tangle of vegetation, vibrating in long 

 undulations with every breath of wind. 



These continuous woodlands, w^hich branch off southwards up the valleys of 

 the Amazons affluents, are continued across the inland plateaux of Brazil by a 

 less densely timbered region, in which the trees stand out wdth more distinct 

 individuality, but which none the less constitutes an immense expanse of 

 true forest, the Matfo Grosso, or " Great Wood," as it is called by the 

 Brazilians. 



Still farther south follow the catingas and the campas, or " fields," that is, 

 open spaces dotted over with araucaria thickets. These are succeeded in the 

 southern parts of the La Plata basin by treeless plains, producing little but low 

 plants, such as grasses and thistles. Here the arborescent vegetation is repre- 

 sented only by a few isolated trees, visible far and wide on the boundless plain. 

 Such are the pampas, corresponding to the llanos north of the equator, that is, 

 the open Venezuelan plains, everywhere encircled by the tropical forest zone. 

 Less extensive than the pampas, the llanos are also less destitute of trees ; in 

 many places the heights, or even the simple rising grounds, are crowned with 

 thickets or clumps of trees, resembling at a distance green islets in a shoreless 

 sea. Here also the streams are lined with a fringe of leafy vegetation. 



All these transitions from dense forests to more open woodlands, from groves 

 and thickets to treeless savannas, correspond with the varying proportion of rain- 

 fall. The regions clothed by the Amazonian forests receive copious downpours 

 nearly throughout the year, the dry season, as it is called, lasting less than 

 three months. The absence of forest growths, as in the llanos, and in the 

 districts of Guiana sheltered from the east winds by coast ranges, is due to the 

 presence of a screen of mountains, by which the rain-bearing clouds are inter- 

 cepted. 



In Matto Grosso and the neighbouring provinces, where the dry season lasts 

 more than three months, the moisture is insufficient to nourish an exuberant 

 ve2"etation such as that of the Amazonian woodlands. It diminishes in the 

 region of the Brazilian campos, and still more in the pampas of Argentina. 

 Lastly, the few deserts of South America, also called " pampas," the sands of 

 Tumbes and of Sechura in north Peru, the Pampa de Tamarugal, the Atacama 

 desert in the territories recently annexed to Chili, all owe their lack of vegeta- 

 tion to the almost total absence of rain. 



The southern extremity of the continent is too far removed from the Ant- 

 arctic Pole for the temperature to destroy the forest vegetation. But the 



