588 WHEAT WHEAT FLY head of food grains, as it contains, besides a large amount of starch, nitrogenous princi- ples, and those mineral elements required by the animal system ; the grain raised in dif- ferent countries or on unlike soils, as well as that of the different varieties, shows consider- able variation in the proximate constituents. The average of recent analyses gives in 100 parts : water, 14'4 ; mineral matter, or ash, 2 ; albuminoids, 13; carbohydrates, 67'6 ; crude fibre, 8 ; fat, 1*5. The important constituents vary between the following extremes : albu- minoids, from 10*7 to 21*5; carbohydrates, 60-2 to 70-2 ; crude fibre, 1'7 to 8-3. As to the mineral constituents, the average of 78 analyses gives the percentage of ash in the grain at 2-07 ; this chiefly consists, in 100 parts, of potash 31'1, soda 3-5, magnesia 12'2, lime 8*1, phosphoric acid 46'2, with sulphuric acid, chlorine, &c. Wheat is mostly consumed in the form of flour, the composition of which depends greatly upon the manner of grinding. When a thin cross section of a wheat grain is examined with the microscope, the surface is found to consist of three layers of cells, the innermost being of longer cells than the outer two; these to- gether form the hull or bran ; just within these are cells con- taining aleurone (a convenient collective name for those gran- ules which consist mainly of albumi- noids), and within these are cells having starch as their chief content, though aleurone and mineral mat- ters are more or less scattered throughout the grain, of which the starch cells make np the body. It is evident that the quality of the flour will depend upon that of the wheat, and the method by which its parts are separated in the mechanical operation of flouring; mill- ers exercise much skill in so mixing the dif- ferent varieties as to produce flour of a uni- form quality. The finest flour is that which most nearly approaches pure starch, though not the most nutritious. After grinding, the whole as it comes from the mill passes into a long cylinder or bolt ; this is an octagonal frame, sometimes over 80 ft. long, about 8 ft. in diameter, inclining } in. for each foot in length, and arranged to revolve ; it is covered with bolting cloth, a sieve-like silken fabric of various degrees of fineness, that near the up- per end of the bolt having the closest mesh ; the meal from the mill, being deposited at the upper end of this, is separated into different degrees of fineness, while the coarser portions pass out at the lower end. The fine flour, about 80 per cent, of the grain, passes through the upper portion of the bolt, while the coarser appears lower down, and is known as mid- dlings, pollard, and by various other local Part of Section of a Wheat limn, magnified. names; the coarsest is shorts and bran. In fine flour the percentage of starch is much greater, and that of the albuminoids and earthy matters less, than in the whole grain ; conse- quently this is not so nutritious as a flour which more nearly represents the wheat it- self. Various expedients have been used for producing a flour which shall contain more albuminoids and phosphates than fine flour; the well known Graham flour should consist of the whole wheat ground fine, but much that is sold under this name is merely bran and shorts subjected to a second grinding ; proper- ly prepared, Graham flour is very nutritious, but, owing to the amount of crude fibre it contains, irritates the bowels of weak persons. Of late there have been several processes in- vented, which propose to first remove the in- ert hull or bran and then grind the decortica- ted grain ; flour prepared in this manner is as fine as any other, and contains much more of the nutritive principles. Whole wheat, pre- pared by soaking, and afterward boiled with milk and sweetened, was formerly used as food in England under the name of frumity. In this country wheat, first carefully freed from its hairs and all foreign substances, ia coarsely ground, and is much used as a dietetic preparation under the name of crushed or cracked wheat, or wheatea grits. The wheat of southern countries contains a larger per- centage of albuminoids than any other, and is used to make macaroni, a favorite food in southern Europe, and imported into this conn- try in considerable quantities. (See MACA- RONI.) Bran and shorts are valuable food for domestic animals, especially for milch cows; bran contains a larger percentage of albumi- noids, fat, and phosphates than whole wheat, and more starch remains with it than is gen- erally supposed. Wheat straw, while it is wasted or even burned to get rid of it by improvident farmers, is of value as food, es- pecially to mix with the more concentrated foods, such as Indian meal and oil cake. The threshing machines break up the straw quite short, and this prevents its being utilized for many of the purposes for which hand-threshed straw may be employed. (See STRAW.) WHEAT FLY, the name given in Europe to the ctcidomyia tritici (Kirby), a small dipter- ous insect of the family of gall gnats, from its depredations on wheat, to which it is nearly as destructive as the famous and closely allied species, the Hessian fly. The perfect insect is -fa of an inch long, orange red, with whitish wings hniry on the edges, and black eyes. They deposit their eggs in the centre of the corolla of the wheat flower, coming out in great numbers between 7 and 9 P. M. early in June, several laying on the same ear ; the eggs are hatched in eight to ten days, and the larvae, footless grubs nearly an eighth of an inch long when fully grown, feed upon the flower, rendering it abortive, and not upon the stem like the Hessian fly ; they are yellow-
