180. The kernel, dry and fairly smooth, has a deep

groove running lengthwise, a number of fine hairs at one

end, and a crumpled irregularity at the other. This

Wheat 171

wrinkling betrays the location of the embryo, or germ,

which is not more than one fourteenth of the entire

berry. The embryo is oily and can easily be removed

with a pin or the point of a knife blade. The remainder

of the berry is endosperm. Cut in two across the groove,

the grain shows plainly under a hand lens three distinct

layers ; the bran outermost and the starchy part inside,

with a layer of dark aleurone cells between.

When wheat is milled, flour comes from the white

interior, the outer two layers making bran. In big

FiQ. 49. — A good yield of wheat, Pennsylvania.

mills the germ is separated from the endosperm and made

into flour, though this weakens the flour and also lessens

its keeping qualities to a slight extent.

181. Varieties, — Like all living things, wheat varies

under diiferent climatic and soil conditions. This is

but natural, for included within the vast range of the crop

are many distinct environments, to which nature and

man attempt to fit plastic plant organisms, particularly

if they are useful. East of the Mississippi, where the

winters are mild and the rainfall abundant, soft winter

wheats are grown. Between this river and the Rockies,

172 The Principles of Agronomy

north of Nebraska, where the summers are dry and hot,

and the winters severe, having little snow, alternate

freezing and thawing injure fall-planted grain; hence,

the farmers grow hard spring varieties. Because the

winters are less rigorous and because snow protects the

young plants from freezing, winter wheats do best on the

Great Plains south of Dakota. The hot, dry ripening

period favors hard grain. On the Pacific coast hard

wheat tends to soften and amber wheat to whiten in re-

sponse to mild winters and wet springs. Both the winter

and the spring varieties are soft and starchy. The types

of wheat in these districts neither begin nor end sharply,

but blend into one another.

All told there are upwards of 1000 so-called varieties.

In 1895, the United States Department of Agriculture

selected about 200 as being best fitted to various regions.

As already indicated, no single choice could be made for

the Great Plains alone. Clearly, then, no one variety

is best for all localities. There are now existing eight

distinct types. Once merely variations, their characteris-

tics have become fairly fixed on account of continuous

selection for one part of the earth.

Certain definite qualities are, however, desired with

reference to which varieties may be improved. Chief

among these are : (1) high yield to the acre, (2) high weight

for a bushel, (3) hardness accompanied by high nitrogen

content, and (4) resistance to drouth, insects, or plant

diseases. Better varieties may be secured by three

methods : (1) by selection of the most desirable plants

from ones now grown ; (2) by cross-breeding ; and (3) by

the bringing of superior species from some other part of

the world that has climate and soil reasonably like the

one in question. Better cultural methods will also

improve the health and consequently the yield of the crop.

What 173

182. Distribution and adaptation. — Although wheat is

primarily adapted to growth in the temperate zone, it is

by no means confined there. It has followed the Cauca-

sian race into every continent and clime, and has also

been cultivated by other races, for example, by the

Chinese and other Asiatics. It is the bread-stuff of

civilized man, having accompanied the spread of

learning and implements. It was first cultivated, as we

have seen, by the Egyptians; all peoples have grown it

except some in the Far East, where a similar grain, rice,

supplants it.

Wheat has matured from the equator to within two

hundred miles of the Arctic circle at Dawson and on the

Mackenzie River, both fully a thousand miles north of the

United States. It is a common crop in Brazil, Peru,

Egypt, India, Australia, United States, Russia, and

Canada. Being best adapted to low plateau regions, it

has spread round the world from east to west, wherever

suitable conditions and opportunities have presented

themselves. Nor is production closely limited by eleva-

tion. In Russia and Palestine, regions fifty to one hun-

dred feet below sea-level produce abundantly, while

Ecuador and Peru show profitable crops at 10,000 feet,

and in the Himalaya mountains wheat is produced at an

elevation of 11,000 feet. About three-fourths of the

crop, however, grows between 500 and 1500 feet above

sea-level.

At the equator the areas of production are high, with

but little growing near sea-level. Near the extremes of

height and latitude, no profit is made from the crop,

production being entirely experimental. The elevation

and latitude of the best regions indicate the desirability

of moderate climates as regards both temperature and

rainfall. With the perfection of dry-farming methods.