In the manufacture of flour, the percentage of the grain recovered in the form of flour varies around 70 per cent. The lowest limit of the grades secured will depend on the markets open to the miller. The amount of merchantable flour recovered is also governed somewhat by the processes of mil ling. There remain always the by-products, known in commerce under the various names of bran, shorts, or middlings.
If a grain of wheat be cut into transverse sec tions, the various parts of which it is composed will be clearly seen. The embryo, which is rejected in milling, will be shown lying along the side opposite that on which is the furrow. Covering the starchy parts of the grain are several layers of fiber or husk, also rejected in the milling process. These layers are technically known as the aleurone, nucellus, testa and pericarp, although these blend more or less into each other according to the con dition of maturity of the grain.
The wheat plant.—The wheat plant is strictly of artificial character and habits. This is well-illus trated by the nature of its growth. It is probable that if cultivation should cease for even a few years the plant would perish from the face of the earth. Under normal conditions wheat completes its round of growth within the limits of each recur ring season. Seeded in the spring it will mature a crop in twelve to twenty weeks, according to season and variety. Its nature has been so adjusted, however, that what are called fall or winter varie ties are cultivated, to a large extent, throughout much of the producing area of the world. These varieties are sufficiently hardy to withstand the winter season, and when planted in the fall will mature the following year, one to two months earlier than those seeded in the spring. There is relatively no variation in the different types and varieties so far as manner of life and growth are concerned.
In germinating, the seed or grain of wheat throws out a whorl of three temporary roots. With the development of the stalk, which immediately takes place, additional whorls are thrown out at each node. The permanent set of roots will be found near the surface branching outward and downward.
If the wheat has been planted deep the stalk may exhaust itself in reaching the surface, and, in the case of alternate freezing and thawing, the slender thread connecting the tiny plant at the surface with the parent seed may be separated too soon and the vitality of the plant be endangered. The
roots of the growing plant may penetrate to a depth of four feet or more, a fact which is somewhat con trary to the common opinion.
While the stems of the wheat are hollow, it is not unusual for them to be more or less filled with pith.
In winter varieties the stalks of the plant do not rise above the crown of leaves, which are first produced, until the advent of spring. The mat of blades which covers the ground serves the useful purpose of protecting the plant throughout the dormant period of the winter season.
During the early growth the nodes are close together, hut soon the wheat begins to joint or "shoot" and the stalks grow rapidly, while the space between the nodes increases until the full height of the plant is attained. The range of the height varies from two to six feet, and there does not appear to be any close relationship between this height of straw and the yield of grain. The less moisture in the soil the smaller the proportion of straw to grain. Ac the plant attains develop ment the spike pushes np until it rises above the growth of foliage below, and a mature field of wheat shows a uniform surface of erect spikes. At this stage of growth the leaves at the surface of the ground, together with those attached to each node, wither and fall, the whole plant turning a golden yellow color.
The ability of the wheat plant to tiller or stool, throwing up additional stalks, is a marked charac teristic. It often occurs that such stools may show twenty to even one hundred stalks starting from a single grain. This habit of tillering is governed by the variety and also may be modified by the climatic conditions of the season. It will readily appear that what is called the "stand" of wheat may depend in a large measure on the freedom with which the plant may send up these addi tional shoots.
The wheat head.—A discussion of the variations existing in the different types of wheat as shown by a study of the spike or head will be given under the classification of varieties. A somewhat tech nical description of the head is, however, necessary in order to make clear many references in this article. The description given is condensed from Bulletin No. 7, Bureau of Plant Industry, United States Department of Agriculture, p. 9.