TRITICUM 105 



the enzymes through the action of which the starches and 

 proteins in the endosperm are rendered soluble (digested), 

 and which in a soluble form, are enabled to pass from cell to 

 cell to the tissues in the growing points. 



The embryo is rich in fat or oil, mineral matter and pro- 

 tein, and contains considerable quantities of soluble carbo- 

 hydrates, but probably no or very little starch. About one- 

 sixth of the embryo is fat and one-third protein, the two 

 constituting about one-half of its weight. 



Bran Layer. — The bran of wheat includes the three outer 

 layers of tissue, viz., pericarp, testa, and nucellus. The 

 pericarp constitutes the larger proportion of the bran and 

 consists largely of mineral and lignified material. The pro- 

 tein content of the bran is due to aleurone cells and starch 

 cells which adhere to bran layers in the milling process. 



Commercially speaking, bran consists of the scale-like, 

 flaky outside covering which is removed from the wheat in 

 the mining process. It ordinarily contains, in addition to 

 the pericarp, testa, and nucellus, all or part of the aleurone 

 layer and some starchy endosperm which may adhere to it. 



Wheat bran varies considerably in chemical composition, 

 and hence in feeding value, according to the kind of wheat 

 used and the milling process employed in grinding it. It 

 may contain as low as 14 per cent, and as high as 18 per cent 

 crude protein, with an average of about 16 per cent. 



Protein of Wheat. — According to analyses of American 

 wheats compiled in 1890, the protein (nitrogen X 6.25) varies 

 from 8.1 per cent, to 17.2 per cent., with an average of 11. 9 

 per cent. This was in samples containing 10.5 per cent, 

 water, thus making the protein 13.3 per cent, of the dry 

 matter of the grain. 



Osbourne and Vorhees have recognized the following five 

 wheat proteins: globulin, albumin, proteose, gliadin, and 



