THE NEOTROPICAL REGIONS 271 



South America 



Tropical vegetation in America readies its greatest development 

 in the enormous area drained by the Amazon and its tributary s. 

 This immense expanse of rich alluvial country lying immediately 

 under the equator, and for the most part having an extremely 

 heavy rainfall, supports the largest area of tropical rain-forest in 

 existence. 



The eastern slopes of the Andes, at the headwaters of the 

 Amazon, receive an enormous rainfall, and this region, and the 

 portions of the Amazon Valley immediately east of the mountains, 

 are covered with a forest growth of unrivalled luxuriance. 1 Further 

 down the river are regions of much lighter precipitation where 

 open savannas occur, while in northeastern Brazil to the south 

 of the mountains of Guiana and Venezuela, the country is said 

 to be very arid due to the interception of the moisture-laden winds 

 from the Caribbean by the intervening mountains. 



The coastal region, however, from the Amazon delta to and 

 including the coast of the Guianas, is one of heavy rainfall, and 

 with very dense forests. This northeast corner of Brazil and 

 coastal Guiana constitute a very natural botanical province. 



The forests of the Amazon region are of three kinds. 2 First are 

 the great forests of the immense regions of the flat valley, which 

 are regularly inundated by the flood-waters, and remain covered 

 with many feet of water for a long period. All trees and shrubs 

 of this flood-forest ("Igapo," "gapo") must be able to survive 

 this long submergence. 



Above the gapo is the great virgin forest occupying land above 

 the flood-mark, and this is the most extensive and luxuriant 

 forest, and contains the greatest number of species. 



Finally, in drier regions are extensive much more open fon 

 of relatively low trees, known by the Brazilians as "Caatinga." 



About the middle of the last century the English botanist 

 Spruce, spent about fifteen years in the Amazonian country, and 

 has given an excellent account of the most important features of 

 this vast region. 



1 Bates, H. W., The Naturalist on tin River Amazon, Reprint in Evxbtman'h 



Library. 



2 Spruce, R., Notes of a Botanist on the Amazon and Andes, edited by Alfred Rus- 



sel Wallace, London, 1908. 



