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238. Species.—No wild species belonging to the genus Zea having with certainty been identified, all the knowledge we have of maize is obtained from its cultivated types, all of which have been considered as coming from one species (Zea mays L.). Apart from pod maize, there are five types or classes which are readily recognizable and when kept pure breed true to type. Although the different types cross readily, intermediate types are not common. The difference in these types is due primarily to the arrangement and character of the endosperm, although accompanied with and resulting therefrom are marked variations in the shape of the grain. (226)

If a dent maize grain is split through its two longest diameters, the endosperm will appear to consist of two parts. In the central part the endosperm will appear white, while on either side it is glossy or corneous (horny). Sturtevant first pointed out the relation between the character of the endosperm and the five types of maize. The several types he has called agricultural species and proposed Latin names for them as follows:

1. Pod maize (Zea tunicata)

2. Pop maize (Zea everta).

3. Flint maize (Zea indurata).

4. Dent maize (Zea indentata).

5. Soft maize (Zea amylacea)

6. Sweet maize (Zea saccfiarata).

In this book these proposed species will be referred to as the types of maize, and variations within these types will be called varieties.

239. Pod Maize.—In this type of maize each grain is covered with a husk in addition to the ear itself being so covered. The plant is excessively leafy, the tassels usually heavy and inclined to produce grains. The plant suckers abundantly. The grains may be of any of the types of maize hereafter described, suggesting that this was the primitive type from which they have been derived, and also, that the differentiation into these types occurred


Pod maize: one-third natural size.

before the podded character became abortive. Reversion is now occasionally seen in cultivated forms. Pod maize is rarely grown even as a curiosity.

240. Pop Maize is that type in which all or almost all of the endosperm is glossy or corneous. Sometimes, perhaps usually, there is a thin layer of white or soft endosperm around the embryo. The grain is usually an elongated oval in outline and extremely hard. The only type with which it can be confused is the flint. The small size of the grain and its property of "popping" makes iden

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tification certain. When the dry grain is exposed for a short time to a high temperature, it explodes into a snow-white fluffy palatable mass, the endosperm being everted about the embryo and hull. This property of popping is connected with the density of the endosperm. A small amount of white endosperm does not unfavorably affect popping, but if the white portion is in excess, as in flint maize, the corneous portion explodes without everting the endosperm.

The varieties of pop maize may be divided into two groups, rice and pearl, with the golden as a rather distinct type of the pearl. The rice pop has a very pointed grain at the top, with a tendency to have the grains imbricated instead of side by side and to have the ears cone-shaped. In the pearl pop the top of the grain is smooth and rounded; the grains are compactly arranged upon the cob and are very dense and lustrous in appearance. The ears are cylindrical.

The plant of pop maize is said to vary with variety, climate and soil from eighteen inches to twelve feet; the usual variation

Pop maize: ear ,lc. variety, being £r0m five t0 SeVen feet . The ten

one-third natural size; grain dency to bear many ears is strongly

pearl variety, about natural « . . ... . i_« t x

^ize marked and the plant is much subject to

sports. The ears vary from one to eight and a half inches; usually from four to six inches in length and from one to one and a half inches in diameter. Variations from eight to thirty rows are reported, with twelve to sixteen rows the most common. An ordinary weight is from three to four ounces per ear.

The following table gives weight and dimensions of the grain of four varieties of pop maize:

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The white rice, nearly a mean between the red rice and the Queen's golden, contained about 4,000 grains to the pound. It would thus take about three pounds of this variety to plant an acre. The rice pops are nearly square in cross section, while the pearl and golden are considerably wider than thick.

Pop maize has been reported from Ottawa, Canada, in North America to Peru in South America, and the evidence indicates a prehistoric culture.1 At present it is extensively grown for human consumption when popped. The season in the United States is reported for different varieties and climates from seventy to 146 days; usually from ninety to 135 days. The white rice variety is most commonly used by commercial growers.

241. Flint Maize is that type in which the split grain shows the embryo and the white endosperm with the glossy endosperm surrounding. The position of the glossy endosperm usually prevents the grain from denting, but when glossy endosperm is thin, the shrinkage of the white endosperm may cause a slight dent . The internal structure serves to distinguish it from the dent type.

The plant varies in height from four to nine feet; usually from five to eight feet. The tendency to be two-eared is considerably stronger than in the dent varieties. As compared with dent varieties, the ears are longer relative to their diameter and are rather more cylindrical, with often a tendency to enlargement at the butt. Ears vary in length from four to twelve, even six 1 U. S. Dept. of Agr., O. E. S. Bui. 57, pp. 15-16.

teen, inches; usually seven to ten inches, with specimen ears twelve inches long not uncommon. The diameter varies from one and one-quarter to two inches; usually from one and threeeighths to one and five-eighths inches. The number of rows on the ear varies from eight to sixteen, with eight rows the most common. Twelve-rowed varieties are more common than tenrowed. A good ear of an eight-rowed variety will weigh from six to seven ounces.

The grains are hard, smooth, and more or less oval, with usually white or golden orange grains, although purple, brown and copper red sometimes occur. In the eight-rowed varieties the typical grain is one-half inch broad by three-eighths inch deep; when more than eight-rowed, three-eighths inch broad and deep; in thickness, all are about one-sixth of an inch. The average weight of 100 grains of an eight-rowed variety is about thirty-three grams, or about 1,400 to the pound. .

This type is reported maturing at 500 north latitude.1 The season varies from ninety to 140 days, 100 to 120 days being the most common. On account of its early maturity, this type is largely and principally grown in the New England States, New York State, Canada and regions of similar climatic conditions for field purposes; rarely a variety is grown for garden purposes.

Following is a list of varieties of flint maize recommended principally for grain production by the stations indicated, including, where possible, the color of the grain of each and the number of years tested:

1 V. S. Dept. of Agr., O. E. S. Bui. 57, p. 16.

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