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silica. They, too, are reduced. If there is an abundance of rain, the cells continue work long, elaborate much vegetable matter, and the plant grows.
If the water supply is insufficient and the soil parsimonious, this prodigious consumption cannot be supplied, and dessication of organs takes place. This begins in the oldest leaves, and nearly always the little leaves at the base of the stem become soft, flabby, and withered. Analyses have been made which show that these leaves let escape some nitrogenized matter, phosphoric acid and potash, which they contained when living, green and turgescent. Thus the closing of one of these groups of little cell factories by the dessication of a leaf is a very important process to the plant, for less vegetable matter is elaborated than if it had continued its work. In dry years a shortening of the stems and a comparatively small amount of straw results.
The dying of leaves involves not only the closing of these workshops, but the transportation of much of the finished product stored in them. Metamorphosis of the nitrogenized matter which forms the protoplasm, the living part of the cell, takes place, and it assumes an itinerant property which enables it to pass through membranous walls and migrate over the liquid highways to new leaves. With it are carried phosphoric acid and potash. Some of the elaborated material is thus continually being transported from lower to upper leaves during the entire period of vegetation. Flowering takes place when enough material has been elaborated to nourish the appearing seeds. This migration of substance can take place only when there is plenty of water, and the crop fails when it is too dry. Too much water is also injurious, for it causes a tendency to keep up growth indefinitely. The Minnesota station found that the wheat plant produced nearly one-half its dry and three-fourths its mineral matter by the end of 50 days. This included 75 per cent of the potash, 80 per cent of the phosphoric acid, and 86 per cent of the nitrogen. At 65 days, 65 per cent of dry and 85 per cent of mineral matter had been produced, as well as most of the fiber, which suffered a loss after 81 days.1 Compared with the processes observed in nitrogenized matter, phosphorus and potash, the 1 Minn. Bui. 29. pp. 152-160.
formation of starch is yet quite a mystery. Its accumulation in the leaves cannot be detected in wheat as it can be in a large number of other species. Neither are reserves of saccharine matters to be found there. It is not until the last stage of vegetation that starch is formed. Consequently climatic influences at the close of the growing period have a marked effect on the amount of starch produced, and cause it to vary greatly from year to year.
The process of transporting elaborated material begins in the planted seed, and does not cease until the wheat is dead ripe. This is the explanation of wheat ripening after it is cut. It also explains the fact that wheat straw, as well as many other straws, is not as well liked by animals, and is not as nutritious, after it is ripe as when green, or when cut before ripe.
Fertilization.—The one-seeded ovulary is a little greenish swelling. It is surmounted by the stigmas, two erect and adjacent aigrettes of plumes. There are three stamens, and the anthers are compactly arranged about the ovulary. At flowering the filaments to which the anthers are attached elongate rapidly. As the anthers are pushed upward, they suddenly overturn, and the pollen falls upon the stigmas, which have
<-«lM *-MAH «-4SAM 4-ff/in 4-55AM 5-OSAJ* S-ISAM 5-18 AM
THE OPENING OF THE FLOWERS OF WHEAT. (AFTER HAYS)
now grow slightly divergent. These delicate operations all take place within the closed flower and generally wheat is thus essentially self-fertilized. The anthers are now pushed outside of the glumes, and the wheat is popularly said to be in flower. As soon as the pollen comes in contact with the stigmas, it germinates by sending out a long tube (called the pollinic branch) into the ovulary. This completes fertilization and the grain is formed. If fertilization in incomplete, the ovularies remain unfertilized, and the spikes bear sterile flowers in which no kernels are formed. It seems that the crop is thus
injured when fertilization takes place in rainy weather. The water probably finds its way within the involucre, and the pollen grains are either imperfectly retained, or their germination is irregular. The process of fertilization generally occurs early in the morning, and may require less than an hour of time. After its completion the ovule (seed) grows very rapidly to maturity. The embryo develops first, and then the endosperm.
The Most Favorable Ripening of wheat requires a mild temperature and a slightly clouded sky. A high temperature the month before wheat is ripe diminishes the yield, and in particular prevents the formation of starch. There is a real, though small, loss in wheat from the period when it is "ripe" to the time when it is dead ripe, and it is claimed that this loss does not result from careless handling, or from drying of the grain.1 Deherain offers the explanation that "all the organs of a plant respire by the aid of the oxygen of the air consuming some of their principles. In the seed the combustion chiefly affects the starch, and a crop which remains standing long diminishes in weight both by the loss of seeds that fall and by the slow combustion which continues as long as desiccation is not produced." What is lost in quantity, however, is perhaps more than gained in quality, for the best flour can be obtained from dead ripe wheat only. Such flour has a better color, and will take more water in bread-making. If the grain is cut before ripe, the most serious feature is increased acidity in the flour. This interferes with fermentation in bread-making, and is liable to make the bread sour or dark.
The Rate of Multiplication of Wheat.—Paley gave 300 grains harvested from one grain sown as a moderate estimate; 400 as a possible one; and 10 to 12 as a practical one. Herodotus said that on the irrigated land of Assyria, wheat yielded from two to three hundred fold, and grew to giant size. Fifty grains of wheat, selected from one spike, were planted, and the 30 grains which grew produced 14% ounces of wheat. This was sown the next year, and produced 5 pecks of grain, which in turn produced 45 bushels the subsequent year. The 45 bushels produced 537 bushels in another year, enough seed from one spike in four years to sow about 500 acres.1 In ten years, one grain of North Dakota wheat, now known as Minnesota 163, without any attempt to increase it rapidly the first few years, actually produced about 300,000 bushels of wheat. One thousand acres of land south of Walla Walla in eastern Washington yielded 51,000 bushels in 1881. "This yield was made the subject of a careful measurement and reported to the Agricultural Department, where it stands today as the largest yield for a thousand-acre field ever reported."2 The greatest wheat crop ever recorded in the world's history as being produced from unfertilized land was that of western Canada in 1901, where 63,425,000 bushels were harvested from a little over 2,500,000 acres; an average yield of over 25 bushels per acre.
1 Kedzie, Rept. Mich. Board Agr., 1881-2, p. 337: Mich. Bui. 191, p. 160; Neb. Bui. 32, p. 87.
Physical Properties.—The number of grains in a pound of wheat varies from 7,500 to 24,000; from 377 determinations the average was 12,000 grains. The number in a bushel has been given as varying from 446,580 to 971,940. The Winchester bushel (2150.42 cubic inches) used in the United States, has a standard and legal weight of 60 pounds. The measured bushel generally varies in weight from 54 to 65 pounds, and greater extremes occur. The Imperial bushel (2218.192 cubic inches) used in England, has a corresponding weight of 61.89 pounds. This is the reason why English wheat appears heavier than American grain.
The specific gravity of American wheat has been found to vary from 1.146 to 1.518. Lyon found high specific gravity associated with low nitrogen content. As a rule, the harder the grain, the higher is the gluten and nitrogen content, and the deeper red the color.
Viability of Wheat.—Experiments have shown the optimum period for germination to be the second year after harvest. Seed one year old often gives better results than fresh seed, but after the first year the viability generally diminishes rapidly from year to year. Ordinarily it is not advisable to sow wheat over two, or at the most three, years of age, at least not without testing its germinating powers, which have been found to vary from 15 to 75 per cent after five years. The longest period for which conclusive modern scientific experiments have shown wheat to be viable is ten years. During six successive years Saunders found the average viability of three varieties to be respectively: 80, 82, 77, 37, 15 and 6 per cent.1 Varro, speaking of the granaries of the first century B. C, remarks that the vitality of wheat can be preserved in them for 50 years. Daubeny questioned this in 1857, and stated that wheat does not retain its vitality over 40 years. Humboldt states that for causes not well known, Mexican grain is preserved with difficulty for more than two or three years. The reported germination of wheat taken from Egyptian mummies thousands of years old is a modern myth originating in the impositions of fraud and cunning upon credulity.
1 Neb. Bui. 32, p. 84.
1 Kept. Bureau of Statistics, Washington, 1903, p. 69.
The highest temperature at which dry wheat seed can retain its vitality is also an unsettled question. Chambers's Cyclopedia makes the statement that some dry seeds survive 212 ° F., and —248° F., but does not state what kind. Klippart gives —58° F. as the point at which wheat loses its vitality, and says that the germinating power is completely destroyed if the grain is steeped 15 minutes in water having a temperature of 122° F. According to the same writer, it could perhaps stand 170° F. in a dry atmosphere without serious injury. He gives this as a probable reason why wheat does not grow in the tropics, where the soil often has a temperature of 190° F. Recent experience has shown that steeping wheat ten minutes in water of 132 to 133° F. to kill smut germs does not injure its viability. In northern Canada, —52° F. has no injurious effect upon the vitality of dry and implanted wheat. Beyond these temperatures, no scientific experiments have been found recorled by the author.
Time Required for Ripening.—The mean temperature required for the successful cultivation and ripening of wheat has been given as 65° F. for 45 to 60 days, and 55° F. for three or four months of the growing season. Of the wheat in the United States, according to the census of 1880, 67.5 per cent was grown where the mean annual temperature was between 45 and 55° F., and 62.7 per cent of it where the annual rainfall was between 35 and 50 inches. It has been claimed that the total amount of sunshine and heat units required to mature a crop 1 Kept. Can. Exp. Farms, 1903, p. 44.