34 



THE CEREALS IN AMERICA 



the side opposite the embryo, causing a deep infolding o£ the 

 pericarp or bran, which makes the roller process of milling a 

 superior method. It is characterized by a small embr}^o, and 

 a large development of endosperm from which the flour is 

 obtained. Bessey estimates the cubic contents of a wheat 



grain to be from 

 twenty to thirty cu- 

 bic millimeters, of 

 which fully thirteen- 

 fourteenths are filled 

 with starch cells, the 

 embryo occupying 

 no more than one- 

 fourteenth of the 

 space. ^ 



6i. The Embryo. 

 — The embryo can 

 be divided into (i) 

 scutellum, or absorb- 

 ent organ, which on 

 germination causes 

 the dissolution of the endosperm and then transfers it to (2) the 

 vegetative portion. This vegetative portion contains in mini- 

 ature the first leaves and roots of the new plant. The embryo 

 contains a relatively high per cent of ash, protein and fat, and 

 considerable quantities of soluble carbohydrates (sugar), but 

 probably little if any starch. About one-sixth is fat or oil and 

 about one-third is protein, the two thus constituting one-half of 

 the embr)/^o. The proteids of the embryo differ also from those 

 of the endosperm in the ease with which they undergo changes. 

 Osborne has found the embryo to contain about 3.5 per cent 

 of nucleic acid.^ 



1 Neb. Bui. 32, p. 103. 



2 Conn. Rept. 1901, pp. 365-430. 



V Qp (S) «> «).®-'(5) ® CD CD c. 



4 mQ 6)- 



Progressive sections of grain of wheat taken at the three 

 axes as indicated, showing shape of grain and position 

 and ratio of (jtr) embryo to (jy) endosperm. (From 

 microphotographs by Rowiee.) 



