532 WHEAT coccum, which undoubtedly grows wild in Greece and Mesopotamia, is cultivated in Spain and elsewhere, and was also cultivated by the aboriginal Swiss lake-dwellers, as well as at Hissarlik, as is shown by the grain l found in those localities. (2) T. sativum is the ordinary culti vated wheat, of which Haeckel recognizes three principal races, spelta, dicoccum, and tenax. Spelt wheats (see fig. 2) were cultivated by the aboriginal Swiss, by the ancient Egyptians, and throughout the Roman empire. The variety dicoccum was also cultivated in prehistoric times, and is still grown in southern Europe as a summer wheat and one suitable for starch-making. Other sub-varieties of T. tenax are compactum, turgidum, and d^^rum (see below). (3) The third species, T. polonicum, or Polish wheat, is a very distinct -looking form, with long leafy glumes; its origin is not known. As these varieties intercross with each other, the presumption is that they, like the species of ^Egilops, which also intercross with wheat, may have all originated from one common stock. Home Basing his conclusions upon philological data, such as and the names of wheat in the oldest known languages, the distribu- wr it m g g o f the most ancient historians, and the observa- tion tions of botanical travellers, De Candolle infers that the original home of the wheat plant was in Mesopotamia, and that from thence its cultivation extended in very early times to the Canaries on the west and to China on the east. In the western hemisphere wheat was not known till the 16th century. Humboldt mentions that it was accidentally introduced into Mexico with rice brought from Spain by a negro slave belonging to Cortes, and the same writer saw at Quito the earthen vase in which a Flemish monk had introduced from Ghent the first wheat grown in South America. Principal As might be anticipated from the cultivation of the plant from varia- time immemorial and from its wide diffusion throughout the eastern tions. hemisphere, the varieties of wheat that is, of T. sativum are very numerous and of every grade of intensity. Those cases in which the variation is most extreme some botanists would prefer to con sider as forming distinct species ; but others, as De Vilmorin, having regard to the general facts of the case and to the numerous inter mediate gradations, look upon all the forms as derivatives from one. In illustration of this latter point it may be mentioned that not only do the several varieties run one into the other, but their chemical composition varies likewise according to climate and season. According to Prof. Church, 2 even in the produce of a single ear there may be 3 to 4 per cent, more of albuminoid matters in some grains than in others ; but on the average the proportion of gluten to starch is as 9 11 to 100. From the point of view of agri culture (see vol. i. p. 354) it is generally of no great moment what rank be assigned to the various forms. It is only important to take cognizance of them for purposes of cultivation under varying cir cumstances. Hence we only allude to some of the principal varia tions and to those characteristics which are found to be unstable. (1) Setting aside differences of constitution, such as hardihood, size, and the like, there is relatively little variation in the form of the organs of vegetation. This indicates that less attention has been paid to the straw than to the grain, for it is certain that, were it desirable, a great range of variation might be induced in the foliage and straw. As it is, some varieties are hardier and taller than others, and the straw more solid, varying in colour and having less liability to be "laid"; but in the matter of "tillering," or the production of side-shoots from the base of the stem, there is much difference. De Vilmorin points out that wheats of cold countries have flexible, thin, hollow straw, elongated fragile ears, and soft floury seeds ; Hunter s wheat may be cited as a good example. Wheats of hotter countries have a more solid, rigid straw, the ears short, stout, com pact, the glumes provided with long awns or beards, and the seed hard and horny. Spring wheats procured from northern latitudes mature more rapidly than those from temperate or hot climates, whilst the reverse is the case with autumn wheats from the same source. The difference is accounted for by the greater amount of light which the plants obtain in northern regions, and, especially, by its comparatively uninterrupted continuance during the growing period, when there are more working hours for the plants in the day than in more southern climes. Autumn wheats, on the other 1 See drawings made to scale by Mr Wortliington Smith in the Gardener s Chronicle, 25th December 1886. 2 Food Grains of India, p. 94. hand, are subjected to an enforced rest for a period of several months, and even when grown in milder climates remain quiescent for a longer period, and start into growth later in spring, much later than varieties of southern origin. These latter, accustomed to the mild winters of those latitudes, begin to grow early in spring, and are in consequence liable to injury from spring frosts. Wheats of dry countries and of those exposed to severe winds have, says De Vilmorin, narrow leaves, pliant straw, bearded ears, and velvety chaff, characteristics which enable them to resist wind and drought. Wheats of moist climates, on the other hand, have broader leaves, to admit of more rapid transpiration. No doubt careful microscopic scrutiny of the minute anatomy of the leaves of plants grown under various conditions would reveal further adaptations of structure to external conditions of climate. At any rate, it is certain that, as a general rule, the hard wheats are almost exclusively cultivated in hot, dry countries, the spelt wheats in mountainous districts and on poor soil, turgid wheats, like the Egyptian, in plains or in ill-drained valleys, the best races of wheat being found on rich alluvial plains and in fertile valleys. The wheat used in the neighbourhood of Florence for straw-plaiting is a variety with very slender stalks. The seed is sown very thickly at the beginning of winter and pulled, not cut, about the end of May, before the ear is ripe. In the United Kingdom ordinary wheat, such as old red Lammas and Chiddam s white, is used for straw-plaiting, the straw being cut some time before the berry ripens. The propensity to " tiller " is of the greatest importance, as it multiplies the resources of the farmer. An instance of this is given in the Philosophical Transactions (1768), where it is stated that one seedling plant in the Cambridge botanic garden was divided into eighteen parts, each of which was replanted and sub sequently again divided, till it produced sixty-seven plants in one season. In March and April of the following year these were again divided and produced 500 plants, which in due time yielded 21,109 ears. (2) The variations in root-development have not been much attended to, although it would be well to study them in order to ascertain the degree of adaptability to various depths and condi tions of soil. (3) A most important difference is observable in the liability to attacks of rust (Puccinia), some varieties being almost invariably free from it, while others are in particular localities so subject to it as to be not worth cultivating. (4) Velvet-chaffed wheats do best in poor soil, and bearded wheats are usually hardi est. (5) The ears vary, not only in size, but also in form, this latter characteristic being dependent on the degree of closeness with which the spikelets are set on. In such varieties as Talavera the spikelets are loose, while in the club and square-headed varie ties they are closely packed. The form of the ear depends on the relative width of the anterior and posterior surfaces as compared with that of the lateral surfaces. In the square-headed varieties the lateral surfaces are nearly as wide as the median ones, owing to the form and arrangement of the spikelets. The number of abortive or sterile spikelets at the top of the ear also varies : in some cases nearly all the spikelets are fertile, while in others several of the uppermost ones are barren. The classification of the different varieties of cultivated wheat Classifi has occupied the attention of many botanists and agriculturists, cation The latest and fullest account is that of M. Henry de Vilmorin in culti- his Lcs BUs Meillcurs (Paris, 1881). The classification adopted by vated this writer is based, in the first instance, on the nature of the ear : wheats when mature its axis or stem remains unbroken, as in the true wheats, or it breaks into a number of joints, as in the spelt wheats. In the first class the ripe grain readily detaches itself from the chaff- scales, while in the spelts it is more or less adherent to them, or not readily separable from them. The true wheats are further sub divided into soft wheats, turgid wheats ( T. turgidum), hard wheats (T. durum), and Polish wheats ( T. polonicum). In the soft wheats the chaff-scales are boat-shaped, ovoid, of the consistence of parch ment, and shorter than the spikelet ; the seed is floury, opaque, white, and easily broken. In the turgid wheats the glumes have long awns, and the seed is turgid and floury, as in the soft wheats. In the hard wheats the outer glumes are keeled, sharply pointed, awned, and the seed is elongated and of hard glassy texture, some what translucent, and difficult to break owing to its toughness. These seeds are richer in nitrogen than the soft wheats, so that an approximate notion of the richness in albuminoids may be gained by simply inspecting the cut surface of the seed. The Polish wheat, rarely if ever cultivated in the United Kingdom, has very large lanceolate glumes, longer than the spikelet, and elongated glassy seeds. Further subdivisions are made, according to the pre sence or absence of awns (bearded and beardless wheats), the colour of the ears (white, fawn-coloured, or red), the texture of the ears (glabrous i.e., smooth or downy), and the colour of the seed or "berry." In the jointed or spelt wheats the distinctions lie in the presence of awns, the direction of the points of the glumes (straight, bent outwards, or turned inwards), the form of the ear as revealed on a cross section, and the entire or cleft palea. As illustrating the fact of the occasional instability of these variations, Prof. Church
mentions that a single grain will be sometimes horny and partly