Rubber is the coagulated sap of more than 300 varieties of tropical trees and vines - the Landolphia of Africa, the Ficus of the Malay Peninsula, the Guayule shrub of Mexico and the Castilloa of South America, Central America and Southern Mexico are all important rubber producers, but far more important than all of the others together is the Hevea, a native of Brazil.

Hevea trees are scattered through the dense forests of practically every part of the Amazon Basin, a territory more than two-thirds as large as the United States.