Grasses

Maize, corn, or mealies (Zea mays) is derived from grasses native to Central America, probably from Mexico. Maize has a very distinctive, flowering structure, with a tassel of male flowers perched above the larger clusters of female flowers. Each of the several female flower clusters is an elongated, head-like structure known as a cob or ear, enclosed within sheathing leaves or bracts, known as husks. Each ear contains as many as several hundred female flowers, each of which may produce a seed known as a kernel. During the time that they are ripe for pollination, and the stigmas of the female flowers are borne outside of the sheathing leaves of the cob on very long styles known as corn silk.

As with wheat, maize occurs in a wide range of cultivated varieties bred for particular uses and climates. The maize plant has been so highly modified by selective breeding for agriculture that it is now incapable of reproducing itself without the aid of humans. The ripe grains of the plant are no longer able to detach from their husk or cob (this is known as shattering). Moreover, the ripe kernels are tightly enclosed within their sheathing husks so that they are trapped by those leaves when they germinate. Modern maize can only be propagated if humans remove the leaves and grains from the cob and sow the ripe seeds.

Some of the presumed, wild ancestors of maize still occur in natural habitats in Mexico. One of these is teosinte (Zea mexicana), a wild grass that does not form a cob encased in husks. Another possible progenitor of maize is a grass called Tripsacum mexicanum that does not look much like corn but will readily hybridize with it. The wild relatives of maize are of enormous importance because they contain genetic variation that no longer is present in the highly inbred races of maize that exist today, particularly the varieties that are used widely in modern, industrialized agriculture. As such, some of the genetic information in the remaining wild species that participated in the cultural evolution of the modern maize plant may prove to be incredibly important in the future breeding of disease resistance, climatic tolerance, and other useful attributes of this critical food plant for humans.

Maize grows well under a hot and moist climatic regime, and it can be cultivated in both the tropical and temperate zones. Maize is used in many forms for direct consumption by humans. During the harvest season, much sweet corn is eaten after boiling or steaming. Maize is also eaten as a cooked porridge made of ground meal (in the southeastern United States, this food is known as grits). Other foods include canned or frozen cooked kernels, corn flakes, tortillas, corn chips, and popcorn. The small, unripe cobs of maize can also be steamed or boiled and eaten as a nutritious vegetable. Corn seeds can also be pressed to manufacture an edible oil.

Much of the maize crop in North America is fed to livestock. The nutritional value of the maize is greatly enhanced if the plants are chopped up and subjected to a fermentation process before being used for this purpose. This type of preparation which can also be prepared from other grasses and from mixed-species hay is known as silage.

In some regions such as the midwestern United States, much of the maize production is utilized to manufacture ethanol for use as a fuel in automobiles, usually blended with liquid petroleum hydrocarbons as a mixture known as gasohol. Other products made from maize include corn starch, corn syrup, and alcoholic beverages, such as some types of whiskey.