WHEAT 533 albumen, "fified with starch. D. Embryo cut through the middle, root -end pointing down wards. opaque and soft, in which case its composition will correspond with its aspect. The division into spring wheat and winter wheat is an agricultural one solely. Any variety may be a spring or a winter wheat according to the time at which it is sown. In the summer wheats it may often he observed that the median florets do not fill out so fully as in the autumn wheats. Among the turgid wheats there is a frequent ten dency in the spike to branch or become com- pound, a tendency which is manifested to a less degree in other B forms. The Egyptian, or so-called "mummy" _ wheat is of this charac ter, the lower part of the spike branching out into several subdivi sions. This multiplica tion of the seed -bear ing branches might at first sight be considered advantageous ; but in practice the quality of the grain is found to be inferior, as if the force that should have been devoted to the maturation of the grain were, in a measure, di- F>. 3. -Longitudinal section of a grain of wheat; , , , , , . highly magnified. A. Epidermal cells. B. Cells verted and expended in c ^^^ gluten. C. Cells of pcrisperm or the production of addi tional branches to the spike. With regard to the chemical composition of the ripe grain, the Rothamsted experiments reveal a singular uniformity, even under very varied conditions of manuring, and even where much diversity was apparent in the constitution of the straw. A high or low per centage of nitrogen in the grain was also shown to depend more directly on the degree of ripening, as influenced by the character of the season, than on difference in manure ; but it depends more upon the variety than upon soil or nutrition. Adapta- Apart from the botanical interest of these diversities, as indica- bility to tions of the faculty of variation in plants, and possibly^ as clues to soil and the genealogy and origin of the cultivated plant, their practical locality, importance is very great. Some varieties are suited to hot, others to cold countries ; some will flourish on one description of soil, others on another. Hence the paramount importance of ascertain ing by experiment, not only what are the best varieties, but which are the best adapted for particular localities and particular climatic conditions. Porion and Deherain have shown : the " infinite superi ority " over the ordinary wheats of a particular square-headed variety grown on rich soil in the north of France. A good selection of seed, according to the nature of the soil, demands, says De Vil- morin, intelligence and accurate knowledge on the part of the farmer. If a good variety be grown in poor soil, the result will be unprofitable, while, if bad wheat be grown on good soil, the result may be nil. In botanical collections there exist, it is stated, her barium specimens or other evidences of plants grown in Norway a far north as lat. 65 (Schubeler), in Switzerland at an elevation of 1200 feet above the valley of Zermatt (or 6500 feet above the sea), near the straits of Magellan, as well as in Teneriffc, the Cape of Good Hope, Abyssinia, Rodriguez, the Philippine Islands, and the Malay Archipelago. These widely -separated localities show the great area over which the culture is possible, and illustrate the powers of adaptation of the plant. The requirements of the con sumer have also to be considered : for some purposes the soft wheats, with their large relative proportion of starch, are the best, for others the hard Avheats, with their larger quantity of gluten. With the modern processes of milling, the hard wheats are preferred, for they make the best flour ; and in North America the spring wheats are, as a rule, harder than the winter wheats. The soft wheats are those which are most general in European cultivation, and, as rule, the beardless varieties, though more tender, are preferred The bearded varieties are supposed to be hardier ; at any rate they defy the ravages of predatory birds more completely than tlu unarmed varieties, and they are preferable in countries liable tc storms of wind, as less likely to have their seeds detached. Hare wheats are specially employed in Italy for the fabrication of maca roni. Polish wheat is used for similar purposes. Spelt wheats are grown in the colder mountainous districts uf Europe ; their flour i very fine, and is used especially for pastry-making ; but, owing t< the construction of the grain, it requires special machinery fo grinding (see FLOUR). The following passage, reproduced from a German source 1 Ann. Agronom., January 1888, p. 33. Agricultural Science (January 1887), may serve still further to illus- rate the fitness of particular varieties for special purposes. " Innumerable experiments have shown that the value of wheat for seed fn- reases with the size of the grain : the larger kernel yields a stronger plant, and his will bear a heavier crop ; the smaller grain contains the larger proportion f gluten, yields a better flour, and brings a higher price ; but with the smaller ield per acre the profit may be less. The volume-weight is dependent more n the well-rounded form of the grain than on its size ; when about alike in espect to shape, the market value of the grain is closely proportionate to its veight per bushel. Grain of a higher specific gravity is usually richer in gluten. Uchness in this constituent is of the greatest importance, as affecting the narket value of the grain ; it gives better baking qualities to the flour, besides i higher nutritive value, and is accompanied with greater richness in phosphate, also an important constituent of animal food. The proportion of gluten in vhcat is determined largely by the climate, and especially by the proximity of he sea. Insular England produces a wheat grain with high absolute weight, jut as a rule with less gluten than the wheat of eastern Europe. English vheat, and wheat in general grown in an ocean climate, seldom contains over
- en per cent, of gluten, while in eastern Europe and in the western United
States the proportion rises to twenty per cent, and above. Vigorous English jeed wheat sown in eastern Europe yields larger crops than the native seed, and a grain richer in gluten than the parent, though not so rich as wheat from native seed." 2 It is, however, to be observed that proximity to the sea does not produce soft wheat poor in gluten in Italy, Algeria, and other varm and tropical regions, where the plant is cultivated quite as much under the influence of the sea as in England. The soft wheat of Great Britain is to be explained rather by the mildness of the climate and the relative constancy of the temperature. Wheat begins to grow at a temperature of 5 C. (41 Fahr. ) ; and, when the aggregate temperature, as represented by the sum of the daily means, has mounted up to 185 Fahr., the germ begins to escape from the husk, if the seed be not deeply buried ; but if it is deeply buried, an amount of heat is required greater in proportion to the depth. If the seed lies at a depth lower than a foot from the surface, it rarely germinates. The seedling plant ceases to grow if the mean temperature of the day remains below 42 Fahr. When the young plants have been influenced by an aggregate tem perature amounting to 1896 Fahr. from the period when sown, or 1715 from the period of germination, branching or " tillering " goes on freely, and the young ears are formed. Under the influence of a mean temperature of 55, or a little above, the flowers are pro duced. A still higher daily mean is required for the full develop ment and ripening of the grain. The figures here cited are given by Risler and are calculated for the climate of Paris ; but, of course, the same principles apply in the case of other countries. The amount of light and of moisture has also to be taken into account. The fact that the wheat plant requires less water than other cereals, and therefore does not suil er so much from drought, is one of great importance to the cultivator, and furnishes one reason for the greater proportionate culture of wheat in the eastern than in the western counties of England. As for the soil requirements, see AGRICULTURE, vol. i. p. 357. The following figures, cited by De Vilmorin from Joulie, will give an idea of the nature and amount of the demands made upon the soil by a wheat crop : in order to yield a crop of 44 bushels of wheat to the acre, the soil must supply to the crop during its growth in round numbers 202 R> of nitrogen, 81 lb of phosphoric acid, 55 R> of lime, 26 lt> of magnesia, and 255 K> of potash. The numerous varieties of wheat now in cultivation have been Produc- obtained either by selection or by cross-breeding. In any wheat- tion of field there may be observed on close inspection plants differing in varieties, character from the majority. If seeds of these "sporting" plants be taken and grown in another season, they may (or may not) repro duce the particular variation. If they do, and the same process of selection be continued, the variation becomes in time "fixed," though it is always more or less liable to revert to its original con dition. By continuously and systematically selecting the best grains from the best ears, Major Hallett has succeeded in introducing "pedigree wheats" of fine quality. But even greater results may be expected from cross-breeding, or the fertilization of the flowers of one description of wheat by the pollen of another. This has been attempted by Shireff, Le Couteur, Maund, and others in the past, and more recently by H. de Vilmorin and Messrs Carter. Under natural circumstances wheat is self- fertilized : that is to say, the pollen of any given flower impregnates the stigma and ovule of the same flower," the glumes and coverings of the flower being tightly pressed round the stamens and stigmas in such a way as to prevent the access of insects and to ensure the deposit of the pollen upon the stigmas of the same flower. This process of self-fertilization is the usual method, and no doubt keeps the variety true or un mixed ; but the occasional presence of varieties in a wheat-field shows that cross-fertilization is sometimes secured. The stamens of the wheat plant may frequently be seen protruding beyond the glumes, and their position might lead to the inference that cross-fertiliza tion was the rule ; but on closer examination it will be found that the anthers are empty or nearly so, and that they are not protruded till after they have deposited the pollen upon the stigma. The separation of the glumes, which occurs at the time of fertilization, 2 See Ritthausen, Die Eiu eisskbrper d. Getreidearten. Hulsenfriichte, und Od-
samen, Bonu, 1872.