Io8 BOTANY OF CROP PLANTS 



according to size, the coarser particles passing on to the 

 next set of rolls. Finally, the pericarp layers are com- 

 pletely separated from the adhering layers of aleurone and 

 starchy endosperm cells. The finely ground parts of the en- 

 dosperm are sifted and bolted. The material that will pass 

 through fine silk bolting cloth is called flour. The larger and 

 coarser particles that remain behind are known as middlings. 

 The middlings are then freed of particles of bran, i.e., purified, 

 and passed between several sets of smooth rolls; the product 

 of each set of rolls is taken to a machine which separates out 

 the fine flour. The number of grades of flour, and of other 

 products, will depend upon the number of sets of rolls, and 

 the mesh of the bolts to which the grain and its ground prod- 

 ucts are subjected. Mills differ much in the grades of 

 material turned out. 



Kinds of Flour. — There are three general sorts of flour: 

 graham, entire wheat, and patent or straight bread flour. 

 ■"Graham flour ^' is the product obtained by grinding the 

 entire kernel of wheat. Its name is after that of Sylvester 

 Graham (1794-1851), a physician and writer on dietetics. 

 "Entire wheat flour" contains about one-half of the coarse 

 bran. In patent grades of flour all of the bran is removed. 

 There are several grades of patent flour, but the most com- 

 mon one on the market is the "straight" or "standard 

 patent." It is usually a combination of the so-called "first 

 patent," "second patent," and "first clear" flours. About 

 72 to 75 per cent, of the total wheat is recovered as "straight" 

 or "standard patent" flour. It is composed of floury endo- 

 sperm alone. The ordinary bread flours belong to this 

 grade. Other products of the milling process are known as 

 "second clear" flour, used for low-grade bread, "red dog" 

 also used for low-grade bread or for cattle feed, and "shorts, " 

 "middlings" and "bran." About 25 per cent, of the grain 



