GRAINS AND STARCHY TUBERS. 253 



I iiave here reproduced one of the sections most correctly 

 drawn by them, showing the contents of a kernel of wheat. It 

 represents a transverse section magnified about thirty diameters. 

 The extreme outer coat (Plate XIV., i) is the epiderm or husk, 

 and constitutes what in milling is called " the bran." It consists 

 largely of cellulose, and contains no important nutritious element. 

 The next layer (2), quite thin, contains some oil and albumen. 

 The rectangular symmetrically arranged layer of cells (3) are 

 filled with gluten. The entire interior (4) is filled with cells 

 of irregular shape containmg starch, and it is of this that the finest 

 wheat flour is almost exclusively made. The more nutritious 

 nitrogenous elements contained in the gluten cells are excluded in 

 the milling, because these gluten cells, being of a darker colour, 

 would, if ground with the flour, impair the extreme whiteness, 

 which, in the estimation of bakers and of most housekeepers, 

 constitutes its chief value. Chemical analysis, however, shows 

 that flour milled from the so-called " whole-wheat," including 

 layers 2 and 3, in which reside certain nitrogenous and other 

 mineral elements, makes a bread much more nutritious and whole- 

 some, though of a darker colour, than that made from the fine 

 wheat flour. In sections of wheat, rye, oats, and Indian corn, 

 only a single row of gluten cells is seen. In barley there are 

 three rows, but in this latter case the cells being smaller the 

 quantity of gluten contained is not so greatly in excess, as the 

 number might indicate. 



No especial difficulty is encountered, and no especial expe- 

 rience is required, in making satisfactory sections of grains. The 

 main precaution is to soften the kernels slightly, and not too much, 

 by immersion in water. If too soft, the starch will fall out of the 

 cells. If too hard, the sections crumble under the knife. Indian 

 corn may be kept moist for twenty-four hours ; wheat four or five 

 hours ; rye five or six ; barley ten or twelve ; and oats not more 

 than one or two hours. The difference in these grains, with 

 regard to the length of time required to soften them, consists in 

 the thickness or hardness of the outer or epidermal coat. This in 

 Indian corn is hard, dry, and oily, and therefore resists the action 

 of water. In oats it is very thin and easily penetrated. Barley, 

 having a very shallow groove, and being surrounded by a thick 



International Journal of Microscopy and Natural Science. 

 Third Series. Vol. VII. s 



