The true origin of new plants introduced to nations around the world, were often hidden in attempts by those nations to claim a particular plant as their own. These false claims were bolstered by travelers and officials alike, all ignorant of botany and of the early Spanish and Portuguese accounts, which told in detail about many plant introductions. Difficulties were further increased by the criminal stupidity and bigotry of many of the clergy, who deliberately destroyed the native books and culture. The Aztecs, for example, had a highly developed body of botanical lore, with botanical gardens and an extensive materia medica. Bits of this survive, saved by the wisdom and zeal of a few far-sighted priests.

The most important of the food plants to come from the New World tropics was maize, or corn. This invaluable plant does not occur wild, but was probably a native of Central America. From there skilled Amerind farmers had extended its range, bit by bit, until, at the time of the white invasion, it was the principal food plant from Quebec and Montana to Argentina and Chile, except in the rainy lowland tropics. All the kinds of corn now known-dent, flint, sweet, pop, soft, and pod-were developed long ago by the Amerinds, who had innumerable varieties, each adapted to a particular locality. They thoroughly understood seed selection and the use of fertilizers. Corn was taken to Europe by the first Spanish voyagers, and it spread rapidly from Spain to the rest of the Mediterranean area.

The Portuguese took it from Brazil to Portugal, Madeira, India, Java, the Molukkas, and to both the east and west coasts of Africa. At the same time the flint corn of Mexico went with the Aztecs to the Philippines, and from there soon reached China. It also reached China from India, so that soon it was claimed as a native of China because it was grown in the remote interior while still unknown over much of the coastal region. In Africa corn soon spread widely south of the Sahara, and became the chief dependence of the natives of South Africa.

Elsewhere corn also became a principal food of the people in the drier and more barren rocky islands of the oriental tropics, such as Timor, Cebu, and Bohol. In Europe it is the principal diet of the Italian peasantry of the Po Valley, and of several Balkan countries. While the greatest use of corn is in feeding livestock, it is likewise important in the production of starch, oil, glucose, and a variety of miscellaneous products that utilize practically the whole plant.

Several species of Solarium that produce tubers are native to the mountains from southwestern Colorado to Chile, and two or three species were cultivated in prehistoric time from Chile to Colombia. Only one of them, our "Irish" potato, Solarium tuberosum, came into general use, and is now cultivated almost all over the world.