1902 Encyclopedia > Wheat

Wheat




WHEAT (Triticum), the most important and the most generally diffused of cereal grasses, is an annual plant, with hollow, erect, knotted stems, and produces, in addition to the direct developments from the seedling plant, secondary roots and secondary shoots (tillers) from the base. Its leaves have each a long sheath encircling the stem, and at the junction of the blade or "flag" with the sheath a small whitish outgrowth or " ligula." The inflorescence or ear consists of a central stalk bent zigzag, now to the one side, now to the other, thus forming a series of notches (see fig. 1), and bearing a number of flat-tened spikelets, one of which grows out of each notch and has its inner or upper face pressed up against it. At the base of each spikelet are two empty boat-shaped glumes or " chaff-scales," -JJ one to the right, the other to the left, and then a series
of flowers, 2 to 8 in number, FlG; Hr-?pP.e,et and flowers of wl
. , ' . , 'A, Spikelet. magnified. B.' Gin
closely crowded together; from side the uppermost are abortive or sterile,—indeed, in some _varieties only one or two of the flowers are fertile. Each flower consists of an outer or lower glume, called the flower ing glume, of the same shape as the empty glume and ter minating in a long, or it may be in a short, awn or " beard '
On the other side of the flower and at a slightly higher level is the " palea," of thinner texture than the other glumes, with infolded margins and with two ribs or veins. These several glumes are closely applied one to the other so as to conceal and protect the ovary, and they only separate to allow of the passage of the empty anthers after fertilization. Within the pale are two minute, ovate, pointed, white membranous scales called "lodicles." 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 a rounded or oblong body, 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. 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 last is a layer of square cells larger and more regular in form than those on each side ; these contain the gluten or nitrogenous matter upon which so much of the nutritive value of the seed depends. This thin layer of gluten cells contains the albumen or perisperm, which constitutes the great mass of the seed, being composed of numerous cells of irregular form and size filled with starch grains. These layers of
cells 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.
Such in brief is the general structure of the wheat plant Origin
as we now know it. Of its principal variations mention an(i.
will be made below. What was
its origin is not known; and
opinion has differed as to whether
more than one species is involved
or whether all the varieties now
known may not have been originally derived from one. The
prevalent opinion
among botanists is
that the wheat plant_
is nowhere found in
a wild condition.
Recently, however,
M. Frederic Houssay
is alleged to have
discovered the plant
wild in the mountains to the east of T
Kurdistan; but the
statement requires
confirmation. Some
of the species of the
genus Jigilops (now
referred to Triticum
by Bentham and
Hooker and by
Haeckel) may pos- FnJ 2_2 Beardless wheat, II. Polish wheat sibly have been the with seed. III. Spelt wheat All much reduced.
sources of our cultivated forms, as they cross freely with wheats. Haeckei, the latest monographer of the genus, 1 considers that there are three species. (1) Triticum mono-

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 found in those localities. (2) T. sativum is the ordinary culti-vated wheat, of which Haeckel recognizes three principal races, spelt-a, dicoccum, and tenax. Spelt wheats (see fig. 2) were cultivated by the aboriginal Swiss, by the ancient Egyptians, and throughout the Eoman 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 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 intercross with each other, the presumption is that they, like the species of jEgilops, 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 tion"*" " writmgs °f *ne most ancient historians, and the observa-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, 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-ll to 100. From the point of view of agriculture (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 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 varieties 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 wdieat Classifi-has occupied the attention of many botanists and agriculturists, cation of The latest and fullest account is that of M. Henry de Vilmorin in culti-his Les Bles Meilleurs (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-wdiat 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

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 be 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- A-
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- FIG. 3.—Longitudinal section of a grain of wheat;
verted arid exnendprl in higMy magnified. A. Epidermal cells. B. Cells
veitettanaexpenaeain contaimIlg gluten. C. Cells of perisperm or
the production of addi- albumen, filled with starch. D. Embryo cut
tional branches to the through the middle, root-end pointing down-
spike. wards-
With regard to the chemical composition of the ripe grain, the Kothamsted 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 percentage 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-o 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, wdiile, 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 as 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 Teneriffe, 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 wheats, 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 a 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 the unarmed varieties, and they are preferable in countries liable to storms of wind, as less likely to have their seeds detached. Hard wdieats 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 of Europe ; their flour is very fine, and is used especially for pastry-making; but, owing to the construction of the grain, it requires special machinery for grinding (see FLOUR),
The following passage, reproduced from a German source in
Agricultural Science (January 1887), may serve still further to illus-trate the fitness of particular varieties for special purposes.
"Innumerable experiments have shown that the value of wheat for seed in-creases with the size of the grain: the larger kernel yields a stronger plant, and this will bear a heavier crop; the smaller grain contains the larger proportion of gluten, yields a better flour, and brings a higher price ; but with the smaller yield per acre the profit may be less. The 'volume-weight' is dependent more on the well-rounded form of the grain than on its size ; when about alike in respect to shape, the market value of the grain is closely proportionate to its weight per bushel. Grain of a higher specific gravity is usually richer in gluten. Richness in this constituent is of the greatest importance, as affecting the market value of the grain ; it gives better baking qualities to the flour, besides a higher nutritive value, and is accompanied witli greater richness in phosphate, also an important constituent of animal food. The proportion of gluten in wheat is determined largely by the climate, and especially by the proximity of the sea. Insular England produces a wheat grain with high absolute weight, but as a rule with less gluten than the wheat of eastern Europe. English wheat, and wheat in general grown in an ocean climate, seldom contains over ten 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 seed 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."
It is, however, to be observed that proximity to the sea does not produce soft wheat poor in gluten in Italy, Algeria, and other warm 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 wdien 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 produced. 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 suffer so much from drought, is one of great importance to the cultivator, and furnishes one reason for the greater proportionate culture of wdieat 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 44J bushels of wheat to the acre, the soil must supply to the crop during its growth in round numbers—202 lb of nitrogen, 81 lb of phosphoric acid, 55 lb of lime, 26 lb of magnesia, and 255 lb 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,

and which permits the egress of the useless stamens after that oper-ation, is stated to occur only under certain conditions of tempera-ture, when the heat, in fact, is sufficient- to cause the lodicles of the flower to become turgid and thus to press apart the glumes. A temperature of about 75° Fahr. is found by Messrs Carter to be the most favourable. From what has been said it will be evident that the artificial fertilization of wheat is a very delicate operation. The glumes have to be separated and the anthers cut away before the pollen is fully formed, care being taken at the same time not to injure the stigma, and specially not to introduce, on the scissors or otherwise, any pollen except that of the variety desired. De Vilmorin's experiments have shown that all the varieties will inter-cross, and that even such a distinct form as the Polish is no excep-tion. From this he concludes that all the forms have originated from one stock and are to be comprised within one species. In the progeny of these crossed wheats, especially in the second genera-tion, much variation and difference of character is observable,—a phenomenon commonly noticed in the descendants from crosses and hybrids and styled by Naudiu "irregular variation." Sometimes characteristics appear in the crossed wheats which are not found in the parent varieties, although they occur in other wheats. Thus, De Vilmorin records the presence of turgid wheats among seedlings raised from a soft wheat fertilized with the pollen of a hard variety, and spelt wheats among the descendants of a soft crossed with a turgid wheat. Other of De Vilmorin's experiments were made wdth the practical object of obtaining improved varieties or forms speci-ally suitable to particular localities. Among those he has raised is one named "Dattel," which is highly esteemed ; it was got from the red Chiddam, a valuable variety, but one in which the straw is defective. By crossing the red Chiddam with the pollen of Prince Albert a new variety has been produced which is stated to be early, very productive, and of good quality, as far as both grain and straw are concerned. Among many varieties raised by Messrs Carter some are very interesting: in one case the seed-parent was a short-strawed, downy-chaffed, awnless variety, the pollen-parent a large bearded American wheat. The offspring exceeded the seed-parent in stature by a foot, and had a smooth chaff and stout thickset ears with minute awns. Some of the crosses were made with the view to secure denser production of awns and thus to render the ears "bird-proof"; others were devised with a view of securing an early ripening variety, which was effected by crossing wdth the Talavera, a known early variety. The progeny was ready for cutting (in the neighbourhood of London) on 21st July 1886. ield of T° show how considerable may be the variations in the produce Iferent yielded by different varieties, the following figures, taken from the arieties. '' memoranda, sheet" of the Rothamsted experiments, may be cited.
For twelve successive years (1871-1882) Sir John Lawes cultivated 26 varieties of wheat, each variety each year in a different field and under different conditions of manuring. From various circum-stances satisfactory averages were obtained during only eight years (1871-1878). The mean produce of all the varieties taken together during that period was 43J bushels (dressed corn) per acre ; the lowest average produce was 36J bushels per acre, furnished by Hallett's original red ; and the highest produce was 53| bushels per acre, .yielded by Rivett's red. As to manuring, the highest mean produce (51| bushels per acre) from 25 varieties taken together was obtained in 1878 on a field where all the 25 varieties were manured with 2 cwts. of nitrate of soda, the previous crop having been turnips, for which farmyard dung was applied, the turnips being partly consumed on the land, partly removed. Here again Rivett's red furnished the best crop (66^ bushels per acre). This variety in almost—but not in all—cases gave the highest produce. The lowest mean produce from all the varieties taken together was 21J bushels per acre in 1879,—a most disastrous season. In that year even Rivett's red furnished no more than 16 bushels per acre, among the lowest on the record, but nearly twice as much as red Rostock, which in the same year yielded only 8J bushels per acre, the manuring consisting of 2 cwts. of nitrate of soda after clover, partly cut, partly '' fed." This same variety in another year and under a different condition of manuring yielded 57 bushels per acre. The disastrous effect of the season of 1879 was manifested not only in diminished produce but in lessened germinative power ; in the season following white wheats appear to have been the worst, the most satisfactory crop in 1880 being yielded by Webb's "challenge," seeds of which were received direct from Stourbridge and not grown on the Rotham-sted farm, as in the case of the other varieties. As to the weight per bushel of the grains of the different varieties at Rothamsted, there was a more limited range than in the case of the absolute weight, the highest mean (63^ tb per bushel) being yielded by the "red nursery " variety, the lowest by Rivett's red (58 j), the general average of all the varieties amounting to 61J lb per bushel. The effect of the bad season of 1879 was also shown here : the general average in that year was only 53J lb per bushel, while in 1876 it was 63J for the same variet-.es. The greatest weight per bushel does not therefore correspond in all cases with the. absolute amount of crop per acre, for a small crop often yields grain of relatively heavy weight. Nor does the same condition of manuring that brings an abundant crop necessarily yield a proportionate return calculated in weight per bushel. The greatest weight per bushel (63J lb in 1876) was secured on the same plot which in the same year yielded less than an average crop, 42J bushels per acre, very-little difference being observable in the different varieties in point of quality, though much in quantity. The lowest average weight per bushel (56 j lb), however, corresponded with a very low total produce, 23^ bushels per acre in 1880, on a poorly manured plot. These figures, added to those representing the cost for rent and taxes, manure, labour, and expenses of production generally, and considered in connexion with the enormous supplies imported from abroad, will show how great are the risks attendant upon wheat cultivation in the United Kingdom under existing circumstances ; but of course they are of little value as regards the growth of wheat in India and the colonies.
The production of wheat, with the use of wheat bread, has in-creased enormously since the extension of railways has made possible the transportation of grain for great distances by land. The annual crop of the world is now estimated at nearly two thousand millions of bushels. Of late years the increase of production has been most notable in southern Russia, Australia, India, and North America.
Wheat is sometimes grown as a forage crop. A variety has been Wheat
introduced from Japan by Messrs Sutton which seems to be very for
useful for this purpose. Although it takes a longer time to mature fodder,
its seed, it flowers a fortnight earlier than other varieties. It seems
also to be a hardy plant, having withstood successfully eight degrees
of frost. From a crop sown on 27th August a sample was cut on
the following 13th October, with a stem more than 2 feet in length
and very thick and succulent, and the autumn was not very genial.
This variety tillers well, so that it makes a complete mass of green
stuff, which is very serviceable either for feeding sheep or for
"soiling." (M. T. M.)
INSECTS, &C, INJURIOUS TO WHEAT.
It will be convenient to arrange the insects injurious to wheat under the natural orders to which they belong, and afterwards to describe one or two other forms of animal life, such as the myriapod, J'olydesmus, and the nematode worm which causes the ear-coekle, for, although these are not insects, they must be taken into account in any description of the animal pests of the wheat crop.

The order Orthoptera contains the mole cricket, Gryllotalpa vulgaris, one of the largest insects found in Great Britain. It ¡3 2 inches or a little \ more in length, of a brownish colour, and covered \ over by velvety hairs ; it is easily re- \ \ cognized by the pecu-liar character N- \ of its anterior legs, which are very strong and short and laterally com-pressed. These in-sects lead a sub-terranean life, bur-rowing through loose sandy soil by means of their fore limbs, which are structurally well adapted for digging. The sexes pair about the middle of June, and the female lays from 200 to 400 eggs in s her excavated some inches below the level of the' ground. After lay-ing her eggs, she
does not, as is very FIG. 1.—Mole cricket. 1, Eggs ; 2, larva; 3, larva after
generally the case first moult; 4, adult. Natural size,
amongst insects, die, but lives to keep guard over the eggs and the young larvae, which appear in about three weeks ; many of the latter, however, she eats. The young larvae at first resemble black ants ; they are very voracious and feed upon the young tender'rootlets of corn and other plants. The adults prefer an animal diet, but do great damage by cutting through any roots which they encounter in their subterranean burrowings, and as these are winding and extensive considerable injury is caused to the crops. One of the natural enemies of mole crickets is the mole, which devours them readily ; they are also eaten by those birds which scratch the soil for worms. They appear to be very sensitive to smell, and a dressing of a quart of paraffin oil to 1 cwt. of ashes or mould, or watering with solutions of quassia and soft soap, will often rid the field of them.
The corn thrips, Thrips ccrealmm, is a member of the order Thysanoptera, which is by some authorities associated with the

Orthoptera. It is a minute insect about 2 mm. long, with a black and brown coloration. The male is wingless ; the female bears four long narrow wings fringed with long hairs. The antennae are eight-jointed. The legs terminate in characteristic swellings; there are no claws. The insects are very active. The larvae are whitish yellow, with bright red eyes, and acquire their wings after the fourth casting of the skin. The damage done to corn crops by these minute insects is often very serious; they secrete themselves under the paleae surrounding the seed, and feed upon the soft juices of the latter. In addition to this, they sometimes cause injury to the plant by attacking the stalk whilst it is soft and full of sap. Owing to their very small size it is ex-ceedingly difficult to devise means for getting rid of them ; much may be done, however, to pre-vent their appearance by keeping the land clean and free from weeds, which harbour them, and by destroying all refuse in wdiich they may
breed, and ploughing in the stubble to a con- pio. 2. Com thrips
siderable depth. (Thrips cerealium),
The most injurious form amongst the Hemi- female; magnified. ptera is Siphonophora granaria (Aphis granaria, Kirby); it attacks wheat chiefly in England, but is also found upon oats, barley, and rye. The young Aphides attack the leaf blades whilst young and tender, and when the ear begins to appear it is covered with numbers of these insects in every stage of development, from the young larva

FIG. 3.—1, Siphoiwphora granaria, winged Aphis; 2, natural size of same ;3, wingless form ; 4, natural size of same; 5, Aphidius avenas; 6, natural size of same ; 7, Ephedrus plagiator; S, natural size of same.
to the perfect insect. The larvae are of a green or dark green colour, with brown antennae and yellow and black legs. The female, which produces the young viviparously, has a green abdomen, bearing two horns posteriorly ; the rest of the body is brownish green, the legs black and yellow, the eyes red. The winged females, which appear late in the season, lay eggs ; but whether these eggs serve to carry the species over the winter or whether this is done by hibernat-ing larvae is not definitely known. Both larvae and females producing them have been found amongst the roots of the wheat plant during the winter. This Aphis is known to occur upon several of the common grasses of England ; hence any grasses growing in a wheat field should be destroyed as much as possible when the pest is in the neighbourhood. Deep ploughing and rotation of crops may also be recommended. In cases where the insects are noticed at an early stage, a dressing of soot or gas lime will serve to check them. Their numbers are kept down by lady-birds (Ooccinella), which should never be killed, and also by two species of ichneu-mons (Aphidius avense and Ephedrus plagiator), which lay their eggs in the body of the Aphides.
The order Diptera includes several insects which are very harm-ful to corn crops. The frit fly, Oscinis vastator, is a very active small fly, with a greenish black metallic lustre, about 2 to 3 mm. in length. The larvae are yellow or light brown, pointed anteriorly. The flies emerge from the chrysalis about April, and the female deposits her little red eggs upon the under surface of the leaf of the wheat; the larva when it is hatched creeps down and bores its way into the terminal bud of the plant, thus arresting all growth of the ear. The larva assumes the chrysalis state inside one of the outermost leaf sheaths. There are believed to be two broods each year. If, as seems probable, the pupae pass the winter amongst the stubble or grass weeds, it is important that these should either be burnt or ploughed deeply in.
Two closely allied species of flies also attack corn crops ; they are Chlorops taeniopus and Chlorops lineata. The former is of a light straw colour, with three longitudinal dark stripes, and a greenish black abdomen ; the antennae are black, the eyes greenish ; and the dark feet have a stripe of lighter colour. It is about 3 to i mm. long. The injury to the crops is caused by the fly laying its eggs between the leaves of the young plant; the larvae which hatch out from these bore their way down the stem from the base of the ear to the first joint; and there they form swellings known to the farmer as the "gout." The ear is aborted or misformed. The dampest part of the field is most subject to attack. Oh. linéala is about 2 mm. long ; the antennae have their two proximal joints yellow, whilst the third is black on its outer side; in its habits this insect resembles Oh. tseniopus, but attacks chiefly barley crops.

The daddy long-legs, Típula olerácea, causes great damage to corn and other crops by the larvae gnawing the young plants wdiilst they are still below the level of the ground. The female deposits her eggs in the ground, or near it in some grass, &c., choosing as damp a place as possible. The larva is provided with a very tough skin and may measure inches in length. It is apodal, and bores its way beneath the surface of the earth by alternately contracting and expanding. It assumes the pupal condition during the later half of the summer. The pupae are provided with backwardly directed spines, by means of which they raise themselves above the level of the ground. As a means of preserva-tion against this pest, ditches and other damp places should be cleaned out. Rooks, which de-vour the larvae at a great rate, should be encour-aged ; and deep plough-ing to bury the eggs and the larvae should be prac-tised, and the land dressed with some such poisonous substance as gas lime be-fore breaking up.
Two species of Cecido-myia are most destruc-tive to wheat. Cecido-myia tritiei, the wheat midge, has been known in Great Britain for over -i
a century. This fly is FlG. 4._Tjaddy long-legs (Tipula olerácea). 1, a little over 2 mm. in Larva; 2, pupa case; 3, insect, natural size; length, of an orange yel- 4> e88s-

low colour, with black eyes; the female is provided with a long ovipositor, by means of which it deposits ten or more eggs in the ears of wheat. The larvae hatch out in about ten days. They are at first transparent, but become yellow, and their colour gradually deepens. Most of the larvae fall off the plant and bury themselves in the ground, where they change into pupae ; some, however, re-main in the ear and are found in some numbers in chaff. The perfect insect emerges from the pupa in the spring. It is probable that more than one brood is produced during the season. The damage caused to the crop is due to the larva feeding upon the soft tissue of the ear and thus causing the seed to be imperfect; some authorities state that it also devours the pollen. Since the larvae exist in chaff, great care must be taken that this does not prove a source of infection, and land which has been badly affected must be ploughed deep, in order to bury them. 0. destructor is well known under the name of the Hessian fly. It was first noticed in Great Britain during the summer of 1886, in Hertfordshire, and within a few months its presence was reported throughout the eastern half of England and Scotland,— a circumstance which led some authorities to believe that it had existed in Great Britain for some little time ; there has been, how-ever, no definite proof of this. The fly has been known in North America since 1776, where it has done very extensive damage, espe- Flo. 5._Hessian fly (Ceeidomyia de-cially during warm moist sum- struetor). 1, Insect; 2, larva; 3, pupa mers. It is known to occur or" flax seed." All magnified, throughout central Europe; in 1879 it made its appearance in Russia, and in four years had spread over the greater part of that country. The female fly is about 3 mm. long, brownish in colour, but becoming black in the thorax and head. The wings are fringed, rounded at their ends, and the third nerve is branched. The an-tennae are also fringed and consist of two globular basal joints,

and 14 to 16 smaller joints, which diminish in length towards the ends. The male fly is smaller than the female ; the abdomen terminates in two claspers. The female lays in the spring 40 or more eggs upon the leaves of the corn plants,—wdieat, barley, and rye ; oats are not affected. The larvae are hatched in about 5 or 6 days, and make their way down to the axils of the leaves, feeding upon the sap which is passing up the stem. After a few weeks they are transformed into the "flax seed" pupae, which are usually found just above the second joint of the stem. From these pupae the autumn brood of flies emerge ; these lay eggs, and their larvae tide over the winter in the pupal condition. Sometimes only one brood is produced in the year. The injury done to the plant by the larvae living upon the sap usually causes the infected plants to bend over just above the second joint; this renders them easily distinguishable from the healthy plants. The numbers of this most injurious insect are fortunately kept down to a considerable extent by parasites. Five species of Chalcididse are known to be parasitic on 0. destructor in America and six in Russia. Fortu-nately these are not absent in Great Britain. When a crop has been infected by this pest, the corn should be reaped above the second joint, and the stubble carefully ploughed in. A sharp look-out should be kept for the appearance of the "flax seed" both in the plant and in samples of corn, especially if the latter has been badly cleaned. Some species of wdieat seem to have a greater power of resisting the attacks of this insect than others, but as yet very little definite information can be given on this point. These two pests do damage to the amount of millions of pounds every year in North America; but none of those mentioned before them are either common or destructive on that continent.
Cephus pygmasus belongs to that destructive group of the Hymeno-ptera, the saw-flies, and is commonly known as the corn saw-fly. The insect is black in colour, with a large head and prominent eyes. The mouth parts are yellow, and in the male the legs are the same colour. The female is darker and has its black ovipositor slightly exposed. Whilst the wheat is still young and tender, the female pierces the stalk below the forming ear and there deposits an egg. The larva, which hatches out in about ten days, is when full-grown about half an inch long, whitish in colour, with a brown head. It differs from the ordinary saw-fly larva in having but three pairs of legs. This larva bores its way down the stem, cutting through the knots, and about harvest time it cuts the stem nearly through at its base. The larva assumes the pupal stage in the lowest part of the stem and remains in this condition till the following spring, when the perfect insect emerges. Plants which have been affected by this insect can easily be recognized by their thin empty ears. Since the insect passes the winter in the stubble, every effort should be made to destroy this wherever the disease has been prevalent.
The caterpillars of some species of Lepidoptera do considerable damage to corn crops. On the Continent the larvae of Agrotis clavis (segetum) devour the roots of wheat and are especially destruc-tive to autumn-sown crops. Tinea granella, a member of the family Tineidse, causes much harm to grain in store. This small moth, of a dusky white colour, lays one or two minute eggs upon each grain ; as soon as they are hatched, the caterpillars bore their way into the grain, and by means of a web bind several grains together. Through these it bores minute passages and lives in them, devouring the substance of the grain. The larvae ultimately withdraw to the angles and corners of the granary; hence, wherever this pest is prevalent, care must be taken to keep the building free from dust, cobwebs, &c. There is a member of the Ooleoptera which is frequently mistaken for the above-mentioned pest. This beetle is known as Trogosita mauritaniea ; it is supposed to have been introduced from Africa. The larva is J inch long, with a whitish body, bearing tufts of hairs and a brown head. It gnaws the corn grains and lives on their contents. The beetle is carnivorous, and is said to compensate for the damage its larva causes by devouring the above-mentioned Tinea granella.
Another beetle, Oalandra granaria, the corn weevil, also attacks stored grain. The eggs are deposited in the grains of corn and the larva spends its life therein, living upon the substance of the grain, and ultimately turning to a pupa. It leaves the grain first upon attaining the mature state.
The larvae of Elater (Agriotes) lineatus and of other species of this genus are amongst the most destructive insects known to agriculturists. They are commonly known as wire-worms from the exceedingly tough character of their skins. The mature beetles are known as skip-jacks, from the power they possess of regaining their normal position wdien placed on their back by means of a loose articulation between the pro-thorax and the meso-thorax. This when put in action causes the beetle to jump into the air, and they usually fall on their feet. The wire-worms have a rather flattened body, yellowish brown in colour ; it consists of twelve segments, and bears three pairs of legs. The larvae live for several years, and then, burying themselves deep in the earth, emerge as the perfect insect in about a fortnight. The beetles pair in June, and the female deposits her eggs upon blades of grass or the sheath-
ing leaves of corn. The best preventative for this pest is clean farming and scarifying the land after harvest, so as to kill all roots wdiich might serve as food for the wire-worms. When a crop is-badly attacked, soot or gas lime may be applied and the land well rolled to compress the earth. The numbers of 4-the larvae are to some extent kept down by moles and insectivorous birds.
The cockchafer, Melolontlia vul-
garis, is injurious to corn crops, in
both its mature and its larval con-
dition. During the former state it
devours the leaves of wheat and of
most other grasses, trees, and shrubs.
The larva, which is very voracious,
lives upon n ots. This larva is very
thick and fleshy, of a whitish hue, ¡¿afrrr*^
with three pairs of legs ; it usually '
lies in a curled-up position. The i 1-
larval condition lasts several years ; FIG. 6.— Wire-worm CEZaierKneahu), but ultimately the larvae become showing insect and larva, pupae, and in this condition live through the winter. Much may be done to prevent the spread of this pest by shaking the cock-chafers from the trees, amongst the leaves of which they hang, and destroying them. They are eagerly eaten by pigs and poultry.
An allied but much smaller species of beetle, Anisoplia hortícola, with much the same habits as the above, also occurs in England, and attacks wheat and grass crops.
Millepedes, although they are not insects, but one of the groups which compose the larger division Tracheata, must be included in an account of the pests which attack wheat. The English species which is most destructive to wheat, barley, and oats is Polydesmus complanatus. Millepedes pass their life underground, and are sometimes mistaken for wire-worms, but can be at once distinguished by the great number of their legs. They affect damp places, which should be drained, and no rubbish or litter should be left lying about.
Ear-cockle is due to the parasitism of a small white nematoid worm, known variously as Anguillula (Vibrio) tritici or Tylenchus scandens or tritici. These worms cause the formation of a brownish black gall upon the wheat ear. When the ear ripens and falls to-the ground, the nematodes escape from the gall and live in the damp earth. Ultimately they make their way on to a young plant, and, as the ear forms, they pass into it and pair inside the gall which has been caused by their presence. The female lays numerous eggs, from which young nematodes hatch out, until the gall is quite full of them. As long as the gall remains hard, the larvae are motion-less ; but they become active in moisture, and develop into the adult state. If the surrounding conditions are unfavourable they will remain in the larval state for years. They are capable of resisting great extremes of heat and cold, and are apparently un-affected by many poisons. Allied species affect the roots of wheat, grasses, and other plants.
For fungoid diseases, see FUNGUS, vol. ix. p. 831, and MILDEW,
vol. xvi. p. 293. (A. E. S.)




Footnotes

See drawings made to scale by Mr Worthington Smith in the Gardener's Chronicle, 25th December 1886.
See drawings made to scale by Mr Worthington Smith in the Gardener's Chronicle, 25th December 1886.
Food Grains of India, p. 94.

For a discussion of the methods of production followed in the United States, as well as in Canada, and for the chemical composition, trade, milling, and statistics of wheat, see Brewer, "Production of Cereals," in Report to tenth census of United States, vol. iii.








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