National Geographic : 1949 Aug
The National Geographic Magazine Purdy, USDA Inside the Bags, Busy Flies Pollinate Onion Flowers In producing certain onion hybrids to increase disease resistance, yield, and other desirable qualities, the plant breeder first removes from the flower head of a pollen-sterile kind all flowers that have opened and thus might have been pollinated with unknown pollen. The head, with its remaining buds, is then enclosed in a cellophane, paper, or cloth bag, together with a number of flies and a flower head bearing the desired pollen. The insects, ordinary blue blowflies, transfer the pollen from one parent to the other when the buds open. After untold generations this thin stream of man had trickled along the length of North America, through Central America, the Isth mus of Panama, and ultimately the full length of South America. Groups stayed behind along the way, as in Central America, and ultimately evolved distinct tribal character istics and cultures. Others pushed on toward somewhat different destinies. As these American Indians in different re gions-even in the two different continents became better adjusted to the environments into which they were going, they learned to take advantage of and even to depend upon the wonderfully productive native plants that they found in their respective parts of the Americas. Two distinct civilization centers developed, and both became main centers of origin of our present important native crop plants. One was in Central America, the other on the slopes and plateaus of what is now southern Peru, Bolivia, and northern Chile.* The Central American area was probably mainly dependent first upon beans, sweet po tatoes, squash, and pumpkins, while the early Andean people grew maize, potatoes, and tomatoes. Before the white man reached the Americas, however, further diffusion of the people had rather thoroughly distributed most of the crops over those parts of all the Americas where they could be grown successfully. "Taming" Wild Vegetables The difference between our cultivated va rieties and the wild forms from which they came is due only in part to the fact that the * See, in the NATIONAL GEOGRAPHIC MAGAZINE: "Further Explorations in the Land of the Incas," by Hiram Bingham, and "Staircase Farms of the An cients," by O. F. Cook, May, 1916.