WHEAT 19 



a deep infolding of the pericarp or bran. The 

 physical parts of the wheat grain and their average 

 proportions are as follows: 



Seed covering or bran 5.0 % 



Aleurone layer enclosing endosperm and embryo 3.5% 



Embryo 6.5% 



Endosperm or main portion of grain 84.0% 



The endorsperm is the portion from which the 

 flour is made. It is made up largely of starch 

 cells but contains also about 8 to 10% of gluten. 



>Fhe aleurone layer is composed of a single row 

 ofTarge cells known as aleurone or gluten cells, 

 but this part is not included in the flour. 



The bran is made up of six layers of cells, the 

 three outer layers being the pod or pericarp, and 

 the inner layers the coverings of the ovule or 

 seed proper. 



The embryo may be divided into the vegetative 

 portion which contains the miniature first leaves 

 and roots of the new plant, and the scutellum or 

 absorbent organ which at germination , dissolves 

 the substance of the endosperm and transfers 

 it to the vegetative portion. The embryo con- 

 tains a high percentage of ash, about 16% of fat, 

 33% of protein and considerable quantities of 

 carbohydrates, mainly sugar. 



VARIATION IN SIZE 



Bessey estimates the cubic content of a wheat 

 grain to be twenty to thirty cubic millimeters. 

 Richardson found an average of 12,000 grains 

 in a pound of wheat. There were variations of 

 8,000 to 24,000 grains to the pound. Thus one 

 bushel of seed in one case would be equivalent 



