and they only separate for a short time when flowering takes
place; after fertilization they close again. Within the pale
are two minute, ovate, pointed, white membranous scales called
“lodicules.” These contain three stamens with thread-like
filaments and oblong, two-lobed anthers. The stamens are
placed round the base of the ovary, which is rounded or oblong,
much smaller than the glumes, covered with down, and
surmounted by two short styles, extending into feathery brush-like
stigmas. The ripe fruit or grain, sometimes called the “berry,”
the matured state of the ovary and its contents, is oblong or
ovoid, with a longitudinal furrow on one side. The ovary adheres
firmly to the seed in the interior, so that on examining a
longitudinal section of the grain by the microscope the outer layer
is seen to consist of epidermal cells, of which the uppermost
are prolonged into short hairs to cover the apex of the grain.
Fig. 2.—I. Beardless wheat. II.
Polish wheat, with seed. III. Spelt
wheat. All much reduced.
Two or three layers of
cells inside the epidermis
constitute the tissue of
the ovary, and overlie
somewhat similar layers
which form the coats of
the seed. Within these
is the albumen or
endosperm, constituting the
flowery part of the seed.
The outermost layer of
the endosperm consists
of square cells larger and
more regular in form than
those on each side; these
contain aleuron grains—small
particles of gluten
or nitrogenous matter.
The remaining central
mass of the seed is
composed of numerous cells
of irregular form and size
containing many starch
grains as well as gluten
granules. The several
layers of cells above
referred to become more
or less dry and inseparable
one from another,
forming the substance
known as “bran.” At the lower end of the albumen, and
placed obliquely, is the minute embryo-plant, which derives its
nourishment in the first instance from the albumen; this is
destined to form the future plant.
The wheat plant is nowhere found in a wild condition. Some of the species of the genus Aegilops (now generally referred to Origin and species. Triticum by Bentham and Hooker and by Haeckel) may possibly have been the sources of our cultivated forms, as they cross freely with wheats. Haeckel considers that there are three species. (1) Triticum monococcum, 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[1] found in those localities. (2) T. sativum is the ordinary cultivated 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. The variety tenax includes four sub-races, vulgare (common wheat), compactum, turgidum and durum (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 inter cross with each other, the presumption is that they, like the species of Aegilops, which also intercross with wheat, may have all originated from one common stock.
Basing his conclusions upon philological data, such as the names of wheat in the oldest known languages, the writings Home and distribution. of the most ancient historians, and the observations of botanical travellers, De Candolle infers that the original home of the wheat plant was in Mesopotamia, and that from there 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.
As might be anticipated from the cultivation of the plant from time immemorial and from its wide diffusion throughout the eastern Principal variations. 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 consider as forming distinct species; but others, as De Vilmorin, having regard to the general facts of the case and to the numerous intermediate 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 Professor Church,[2] even in the produce of a single ear there may be 3 to 4% 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 agriculture 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 circumstances. Hence we only allude to some of the principal variations 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. 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 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 (durum forms) and common wheats in plains or in 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 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 subsequently again divided, till it produced sixty-seven plants in one season. In March and April of the following year these were again divided
