Popcorn. Zea (Mays) everta. Graminece. Figs. 642, 643.
The popcorns are a special group of flint corns used for "popping," as the name suggests, for eat ing out of hand or in confections. They are char acterized by the small size of the kernels and their excessive hardness, and by the excessive proportion of the corneous endosperm or horny substance con tained in the kernels, which in turn contains a large percentage of moisture and gives the kernels the property of popping or turning almost com pletely inside out on the application of heat. In structure and composition popcorn varies but little from ordinary flint and dent corns, but since it yields so much less it is never grown for market as a stock-food. The stalks of popcorn are con siderably smaller than those of field corn and vary in height from four to twelve feet, with a general average of about eight feet. In color they are usually rather lighter green than the flint corns, but may vary through all the shades of green, and even to a very dark red in some instances.
The actual popping of the kernels has been shown to be due to the expansion of moisture in the starch-celLs, the application of heat converting the moisture into steam, making the cell-walls give way and causing an explosion with sufficient force to alter the entire form and texture of the kernel.
The value of popcorn lies almost wholly in its tendency to pop completely into a large, irregular, flaky mass, since this is the only form in which it has a sufficient value as an edible product to make it worthy of cultivation. While in popping it loses in weight about 10 per cent, due to the evaporation of moisture by the heat employed, it should in crease in bulk in the ratio of at least sixteen tc one, and under the best conditions as high as twenty to one. There are several factors which control this result, such as the even application of heat and the condition of the corn. It may be too damp or too dry for best results, and since the moisture content is high when the corn is harvested, it is usually held over one season before marketing.
Distribution.
Popcorn is grown successfully throughout the northern half of the United States wherever other corn can be grown, and to a small extent on the heavier soils of the Piedmont section of the south ern states, However, there has been a wide change in the methods of production within the last quar ter-century, and whereas it was at one time planted in nearly every garden throughout New York and the New England states, it has gradually come to be a sort of special farm crop grown in a com mercial way by men who have found it profitable and have made the growing, handling and market ing of the crop a special study. This change is also
coincident with the development of certain parts of the Middle West which, because of soil and cli matic conditions, have proved especially adapted to the growth of the crop. The great bulk of the crop is now grown in Iowa, Michigan, Illinois, Wisconsin and Nebraska.
Some idea of the magnitude which the business has attained in certain favored localities can be gained from the statement that from one shipping point in Iowa in 1905 there were shipped more than three hundred car-loads of popcorn.
Varieties.
There are about twenty-five different varieties of popcorn, but these are simply variations of the two distinct types or classes known as rice corn and pearl corn. (Fig. 643.) The rice corn has kernels more or less pointed, with the outer coat, where the silks were attached, continued into a sort of spine, which may either stand almost erect or may be depressed by the crowding of the husk on the ear. The pearl corn has kernels rounded or flattened over the top and very smooth, the point of the attachment of the silk being lower down on the same side of the kernel as the germ. These two classes may be divided into early, medium and late, and these again into white, yellow, and colored (not yellow).
All of these varieties cross with each other so readily that it is difficult under ordinary methods to keep a vari ety strictly to any given type. The different va rieties of both the rice and pearl corn may vary as to color through the several shades of white, amber, yellow, red and black, also red and white striped.