494 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1931 



example, archeologists are finding that agricultural improvements 

 of the megalithic age were not maintained in the classic period. 



INTERCHANGE OF CROPS 



That the world had need of the American crop plants is shown by 

 the wide distribution that many of them have attained in Europe, 

 Asia, and Africa. Some are grown more extensively in the Old 

 World than in America. The potato is the chief dependence of 

 northern Europe, and maize is a staple food in parts of Spain, Italy, 

 Hungary, and many other countries. Cassava has become the prin- 

 cipal root crop in parts of tropical Africa and of the East Indies. 

 An acre of cassava is said to yield " more nutritious matter than six 

 times the same area under wheat." The manufacture of tapioca 

 from cassava is now conducted in the East Indies as well as in 

 Brazil. The sweet potato was distributed across the Pacific and is 

 well-nigh universal in tropical and subtropical regions. The peanut 

 or ground nut is grown commercially in Senegal and in several other 

 districts of Africa and Asia. The principal production of cacao is 

 in West Africa. The vanilla plant grows wild in Mexico, but most 

 of the commercial vanilla comes from the French colonies. Sisal 

 is grown in East Africa and in the Philippines. The Hevea rubber 

 tree, a native of Brazil, is cultivated extensively in the East Indies. 

 Quinine and cocaine are supplied from the East Indies, though the 

 plants are native in Peru. 



Some of the Old World crops, on the other hand, are grown most 

 extensively in America. Taking a plant to a new region may enable 

 it to escape pests or diseases which tend to increase in long-established 

 cultivations. The fungus which destroyed the coffee plantations of 

 the East Indies has not reached America, where most of the world's 

 supply of this beverage is now produced. Brazil is the great coffee 

 country, though coffee is important also in Colombia, Venezuela, 

 Guatemala, El Salvador, Costa Rica, Haiti, and Puerto Rico. The 

 largest commercial cultivations of bananas are in Central America 

 and the West Indies, whence 63,530,000 bunches were imported into 

 the United States in 1929. More sugar is grown in Cuba than in any 

 other countrj^, in favorable seasons more than 5,000,000 tons being 

 produced. Rice from Louisiana and California is shipped to tropi- 

 cal America, Japan, and China. Our high-priced labor raises food 

 for low-price countries. 



TROPICAL AGRICULTURE IN THE UNITED STATES 



Though we are not accustomed to think of the United States as a 

 tropical country, three of our principal crops — maize, cotton, and 

 tobacco — are treated in European textbooks as tropical cultures and 



