Corn (Zea mays L.), or maize as it is called in countries other than the USA, is one of the most important and most remarkable cereal crops in the world today. It is one of the world's most diverse crop species. No other cereal has a greater range of adaptability. It apparently originated in pre-Columbian times somewhere in Mexico and Central America from where it spread northward to Canada and southward to Argentina (Galinat, 1977, 1979). It became the basis of the pre-Columbian American Indian civilizations and still continues as the great economic backbone and as the staff of life for all the New World civilizations, including our own. Types evolved which were adapted to the highlands (at 3000 m or more, where 270 to 395 d may be required for maturity of the crop), to the humid tropical coasts, and to a wide assortment of intermediate conditions.