CHAP 

 XIII. 



660 



MAIZE 



from <)\ to 12 per cent of the whole grain ; is particularly rich 

 in oil (82 percent) and ash, and carries one-fifth of the protein of 

 the whole grain. In the process of manufacture of hominy and 

 starch-products the embryo is usually separated and treated as 

 a by-product under the name of " germ ". 



Table CII. 

 PERCENTAGE COMPOSITION OF THE EMBRYO. 



615. The Endosperm. — The endosperm of the grain is not, as 

 we have seen, homogeneous, but consists of two very distinct 

 portions, the " horny " and the " white starchy " parts ; the horny 

 portion is further subdivided into two parts, the " horny gluten " 

 and the "horny starch". The horny part is readily distin- 

 guishable by its translucence when the grain is held up to the 

 light, and the relative proportion of translucent horny endosperm 

 and of white starchy endosperm forms some guide to the relative 

 feeding-value of the grain. 



616. The Horny Gluten. — The " horny gluten " or aleurone 

 layer lies immediately beneath, and is usually much thicker 

 than, the hull. It constitutes a second covering of the seed 

 and surrounds the starch ; in some breeds of maize it is readily 

 distinguishable because it carries the colouring matter of the 

 grain. The amount of horny gluten varies greatly in the grain 

 (Hopkins notes variations between 5-12 per cent and 14 per 

 cent), and may be increased by breeding. It does not consist 

 of pure gluten, but is richer in percentage of protein-content 

 than any other single part, though it contains only 16} per 

 cent of the total protein-content of the grain. 



