124 NORTH AMERICA 



of the islands to-day, as it was in the time of the 

 aboriginal Cebunaya populations (related to the Mayas) 

 which have vanished before the Europeans. 



CHAPTER III 



SOUTH AMERICA 



General. The wealth and variety of forms of plant- 

 life in South America, offered perhaps by no other con- 

 tinent, are due alike to its situation, its extension in 

 latitude, to the height and disposition of its relief, and 

 to its geological history. The greater extent of its 

 area lies between the Tropics within the belts of 

 equatorial rains and trade-winds. The effect of the 

 constant equatorial heat and moisture is enhanced by 

 the development of a huge alluvial plain which they 

 have helped to create; hence the Amazon selva has no 

 equal in the world. 



Under the latitudes of the trade-winds, high marginal 

 rims prevent the penetration of the moisture very far 

 inland, a fact which favours the extension of broad 

 savanas. Outside the Tropics, the lofty range of the 

 Andes has the same effect on the westerly winds as the 

 triple barrier of mountains has in North America ; hence 

 a similar arrangement in the distribution of the large 

 masses of vegetation, though the Patagonian semi-desert 

 finds no equivalent in the northern continent. 



Central America. The whole land, including Central 

 America up to the Isthmus of Tehuantepec, and reaching 

 south to the Gulf of Guayaquil, east ward through northern 

 Venezuela to Trinidad, along the slopes of the Andes and 



