STRUCTURE OF MAIZE 1 55 



maize grain are examined under the microscope, no material 

 difference in structure is noticeable. This has led to the 

 suggestion, not positively proven, that the difference bet^veen 

 the white and ti-anslucent portions of the endosperm is a differ- 

 ence in density analogous to the difference betAveen snow and 

 ice. The difference is readily noted in pop maize before and 

 after popping. 



Hopkins reports finding corneous endosperm to contain two 

 per cent more protein than the white endosperm in a dent 

 variety, and makes this the basis of selecting strains of maize 

 for high protein.^ The question may be raised whether the 

 higher percentage of protein found in the corneous endosperm 

 may not be due to lack of complete separation from the aleurone 

 layer. On the other hand, a somewhat similar condition exists 

 in the endospenn of wheat. (62) Analyses of dent, flint, pop 

 and soft varieties of maize in which there are wide differences 

 in the densit}^ of the endosperm do not show material differences 

 in the per cent of protein in the whole grain. 



The endosperm occupies about seventy-three per cent of the 

 grain, contains about sixty per cent of the protein, four per cent 

 of the fat, twelve per cent of the ash and about eighty per cent 

 of the carbohydrates, principally starch, of the whole grain. 



The endospenn contains six to ten per cent of protein, eighty- 

 nine to ninety-three per cent of carbohydrates and usually less 

 than half a per cent each of ash and fat It appears probable 

 that the fat found in the endosperm on analysis may be there 

 through absorption from embr}'0 and aleurone layer, since the 

 per cent of fat in endosperm is found to increase with the age 

 of the grain.2 In sweet maize the starch has been changed in 

 part to sugar. 



227. The Aleurone Layer is relatively larger than in the 

 wheat grain, comprising from eight to fourteen per cent of the 



I lU. BuL S7, pp. 83-84. 

 « IlL BuL 87. 



