Other English names: Indian Corn, Maize.
Botanical description: Corn is one of the tallest and most vigorous of the annual grasses. The stems, which vary in height in different types and varieties, are solid, whereas in most other grasses-they are hollow. The leaves are long and broad, wavy and gradually tapering towards the apex. The top of the stem bears a large panicle with spreading branches, each of which forms a spike with numerous-flowers. These flowers contain only the stamens or male organs and are normally unable to form seeds. The seeds are developed in the ear, a kind of fleshy spike, the flowers of which are arranged in distinct rows and contain only the pistils or female organs. When young the ears are enclosed within a husk of broad leaves and nothing can be seen of the flowers. At flowering time a cluster of long, slender, yellowish-green or reddish threads protrude from the top-of the ear. These threads, called the silk, are the top ends of the female flowers and catch the dust-like pollen developed in the male flowers and transported by the wind. The development of the ear starts, as in all other inflorescences of grasses, at the base and proceeds upwards. Thus the first visible silk threads belong to the lower flowers, which consequently, under normal conditions, are fertilized earlier than the upper ones. Should the weather during the latter part of the flowering period be unfavourable, the pollen will not be freely transported and deposited on the silk and the upper part of the ear may be partly or wholly barren, as the seeds are unable to-develop properly without fertilization.
Geographical distribution and history: Corn is undoubtedly of American origin. It was grown by the Indians long before the discovery of America. The Incas of Peru are said to have built large storerooms for it, to prevent famine in case of crop failure. It was grown as far north as the St. Lawrence valley when the first explorers arrived there. Ears of corn are often found in old Indian tombs, deposited with the deceased as provision for the long journey to the happy hunting grounds.
Where or when it was first cultivated, or from what wild plant it developed, is not definitely known. It is generally assumed that its cultivation started in Central America and spread north and south. It has never been found wild. This might either mean that wild corn was extinct before botanists could make a record of it, or that it is a plant so different from the cultivated form that it is now impossible to recognize it. The latter assumption is the one generally favoured, and the plant mentioned as the probable primitive form is the Mexican Teosinte (Euchlaena mexicana Schrad.). Although very different from corn in its general appearance, Teosinte is evidently closely related to it, as is shown by the fact that hybrids obtained by crossing the two produce germinable seeds. Though this is not conclusive proof, it is evidence that corn may have developed from Teosinte, for in all other known cases hybrids between distinct grass species are sterile.
Climate: Being of southern origin, corn requires a warm, moist climate. In the north, where the season is short and the weather comparatively cool, only the earliest varieties reach full maturity under ordinary conditions.
Soil: It demands a warm, fertile soil and thrives best in a deep, rich loam, well drained yet stored with abundant moisture. A good supply of organic matter, furnishing readily available plant food, will increase the yield considerably. Poor sandy soils, or soils with the water table near the surface, do not allow the roots to gather sufficient nourishment. In stiff clay, or in soils which form a hard-pan subsurface, the growth is slow and the yield uncertain, especially in dry weather.
Varieties: Corn includes hundreds of agricultural varieties. This is chiefly due to the readiness with which cross-fertilization takes place between individuals of different types. Some varieties are dwarfs, no more than eighteen inches high; others are giants, reaching a height of from twenty to twenty-five feet. In some the ears are only an inch or two long; in others as much as sixteen inches. The number of kernel rows, which is always even, ranges from eight to twenty-four or more, according to variety. Abnormal individual ears sometimes have as few as four in some varieties, or as many as forty-eight in the large-eared sorts. The size of the kernels, their shape, colour, chemical composition, etc., are extremely variable. According to Dr. E. L. Sturtevant, the varieties may be classified into the following seven principal groups.
1. The pod corns have each kernel enclosed in a pod or small husk and the ear thus formed is also enclosed in husks. All other groups have naked kernels within the husks. It is doubtful, however, whether the pod corns form a natural group. Possibly the husks surrounding the kernels are abnormal and might be found in any of the main groups. This opinion is supported by the fact that the kernel structure varies in the pod corns.
2. The pop corns are characterized by an excessive proportion of the corneous endosperm; that is, the nutritious matter, which forms the greater part of the kernel and is stored for the use of the sprouting germ, contains little starch. In this group the kernels and ears are small. The property of popping over a fire, which is the complete turning inside out of the kernel through the explosion of its moisture content, is most pronounced in varieties which have a corneous endosperm throughout and is less marked as the percentage of starch increases.
3. The flint corns may be recognized by the central part of the endosperm being starchy and completely surrounded by a corneous coat, varying in thickness in different varieties. Cartier found varieties of this group in the neighbourhood of Montreal.
4. The dent corns have the central starchy part of the endosperm surrounded by a corneous layer at the sides of the kernel only, the starchy endosperm thus extending to the summit of the kernel. When the endosperm dries and shrinks, various indentations are formed on the summit of the kernel. The dent corns are extensively grown in the United States, the number of varieties exceeding that of all other varieties combined.