Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/570

WHEAT 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 Iodides 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 auch 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 Naudin "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 with 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 with the Talavera, a known early variety. The progeny was ready for cutting (in the neighbourhood of London) on 21st July 1886. Yield of To show how considerable may be the variations in the produce different yielded by different varieties, the following figures, taken from the varieties. " 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 43 bushels (dressed corn) per acre ; the lowest average produce was 36 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 21 1 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 8| 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 ] >roduce but in lessened germinative power ; in the season following M hite wheats appear to have been the worst, the most satisfactory crop m 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 ft per bushel) being yielded by the "red nursery " variety, the lowest by Rivett s red (58|), the general average of all the varieties amounting to 61| ft per bushel. The effect of the bad season of 1879 was also shown here : the general average in that year was only 53 ft per bushel, while in 1876 it was 63^ for the same varieties. 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 beavy 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 (63 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- tb), 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. 1 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, Polydesmus, and the nematode worm which causes the ear-cockle, 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 Orthoptcra contains the mole cricket, Gryllotalpa vulgaris, one of the largest insects found in Great Britain. It is 2 inches or a little more in length, of a brownish colour, and covered over by velvety hairs ; it is easily ro- cognized by the pecu liar character ^ of its anterior legs, which are verv 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 an oval cham ber 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 larvse, which appear in about three weeks ; many of the latter, however, she eats. The young larvas 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 cercalium, is a member of the order Thysanoptera, which is by some authorities associated with the 1 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-