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class they belong. Some of the most common and widely used classifications are those based on time of sowing, as spring and winter wheat; on firmness of structure of the grain, as hard and soft; on the products for which they are used, as bread and macaroni wheats; and on the color of the seed, as red and white. As will later be shown, wheat adapts itself to new environments so that any one of these classes may be transformed into any other, and as wheat is raised so widely as to embrace practically every kind of environment, these classes grade into each other so imperceptibly that even an expert can hardly determine to which class a certain wheat may belong. An approximate division has, however, been made. Mr. M. A.
Carleton,' cerealist of the United States department of agriculture, has divided the wheat grown in the United States into eight classes, and has shown the distribution of these classes by districts in the accompanying map.
On the north Atlantic coast is the soft wheat district, south of the Great Lakes the semi-hard district, and south of these two districts is the southern district. The Red river valley is
* U. S. Dept. Agr., Div. Veg. Phys. & Path., Bul. 24.
the center of hard spring wheat, Kansas of hard winter wheat and north central Texas of durum wheats. White wheat is raised on the Pacific coast. The center of red wheat, not shown in this division, is from Kansas to the Red river valley. A still more general classification by the same author divides the United States crosswise into three divisions of approximately equal width, assigning the hard wheats to the northern states, the soft wheats to the states of the middle latitudes, and the durums to the southern states. About two-thirds of the wheat raised in the United States is winter wheat. Nearly 90 per cent of the wheat grown in Russia is spring wheat. In Canada, Manitoba raises spring wheat exclusively, but Ontario and Alberta raise some of the winter variety. In Germany, over 90 per cent of the wheat grown is of the winter variety, which is largely grown over southern Europe and on the British Isles. Spring wheat was once more generally called summer wheat, and winter wheat is often also called fall wheat.
Carleton, on a geographical basis, located groups of varieties having special qualities approximately as follows:
1. Starchy white wheats: Pacific coast and Rocky Mountain states, Chile, Turkestan, Australia and India
2. Amber or reddish grained wheats, also starchy: Eastern states, western and northern Europe, India, Japan and Australia.
3. Wheats with excellence of gluten content for making bread: Northern and central states of the plains, Canada, eastern and southern Russia, Hungary, Roumania and southern Argentina.
4. Wheats resistant to orange leaf rust: Southern Russia, Mediterranean and Black Sea regions, and Australia.
5. Wheats with excellence of gluten content for making macaroni: Southern Russia, Algeria, and the Mediterranean region in general.
6. Wheats with stiff straw, which prevents lodging: Pacific coast states, Japan, Turkestan, Mediterranean region and Australia.
7. Wheats with great yielding power (at least in proportion to size of head): Pacific coast states, Chile and Turkestan.
8. Non-shattering wheats: Pacific coast states, Chile, Turkestan, Germany (spelts), and East Russia (emmers).
9. Wheats of great constancy in fertility: Germany (spelts) and southern Europe.
10. Wheats of early maturity: Japan, Australia and India.
11. Wheats most resistant to drought and heat: East and South Russia, Kirghiz Steppes, Turkestan and southern Mediterranean region.
12. Wheats most resistant to drought and cold: East Russia.
Species.—There are eight principal types of cultivated wheat: Einkorn (Triticum monococcum); Polish wheat (Tr. polonicum); Emmer (Tr. sativum dicoccum); Spelt (Tr. sat. spelta); Club or Square-head wheat (Tr. sat. compactum); Poulard wheat (Tr. sat. turgidum); Durum wheat (Tr. sat. durum); and Common wheat (Tr. sat. vulgare).
Varieties.-In 1900, after five years of experimentation with about 1,000 varieties of wheat collected from the different wheat countries of the world, the United States department of agriculture decided that, tested by American conditions, there were 245 leading varieties. No one variety is best under all conditions, but climate, soil, and the purpose for which wheat is raised must in each case determine which variety is most profitable. If a variety can be secured that will yield more under the same conditions than other varieties do, then profits can be easily increased, for its production involves no additional expense, except possibly an extra outlay for seed. Prof. W. M. Hays estimates that Minnesota No. 169, a variety of wheat introduced by the Minnesota experiment station, has increased the yield of that state from 5 to 10 per cent.
The most widely and universally grown varieties of wheat in the United States are Fultz for soft winter, Turkey Red for hard winter, Fife and Blue Stem for hard spring, and Kubanka for durum wheat.
DESCRIPTION AND GROWTH.
Roots.—The first root appearing is called the radicle. This and the two other roots that soon appear form the whorl of three seminal or temporary roots. The crown of roots usually
se of the crowds run at an Most of the
grows about an inch beneath the soil, irrespective of the depth to which the grain was planted. From the crown are thrown out whorls of coronal or permanent roots. Any node of the wheat stalk under or near the soil may also throw out a whorl of permanent roots, somewhat similar to those of corn. There are four or five whorls with three to five roots each. The roots from the base of the crown strike directly downward, while those from the later whorls run at an angle for a few inches before taking a vertical direction. Most of the main roots penetrate to a depth of over 4 feet, perhaps 5 or 6 feet, provided the water-line is not closer to the surface than that distance, for below this the roots will not enter to any appreciable extent. The roots of wheat have been traced to a depth of 7 feet, and it has been found that if those of one plant were placed end to end they would reach 1,704 feet. The deep roots are all fine threads of practically uniform diameter throughout their entire length. They branch and rebranch freely to a depth of 18 or 20 inches, about eight branch roots occurring to an inch length of a main root. At a greater depth, branches are few or absent, and it is supposed that the deep roots are for securing moisture. The roots do not branch or feed much in the region just below that stirred by the plow, if that region is hard and gummy, as is often the case. The upper whorls give forth roots that are larger and coarser, and which resemble the brace roots in corn. It is said that the roots extend chiefly at their extremities, while the stem elongates equally, or nearly so, in all of its contiguous parts. The root development seems to be greatest in durum wheats. Early spring and summer rains cause shallow rooting. In the absence of these rains in the far west, a deeper root system, capable of resisting superficial droughts, is developed. Poor soil causes the roots to age rapidly.
Culms.--The culms of wheat are usually hollow, but in some varieties they are quite filled with pith. The length varies greatly in different varieties, soils and seasons, a fact which results in greater variation in size and yield of straw than of grain. Common wheat averages from three to five feet in height. The liability of lodging depends greatly on the culm, the length of which is also important in harvesting.
1 Hunt, Cereals in Amer. (1904), p. 27.