THE WHEAT GRAIN AND PLANT 



15 



to 50 grains, are usually formed on a spike of wheat, the aver- 

 age length of which is between 3 and 4 inches. Huinboldt said 

 that in Mexico each spike of wheat averaged 90 grains, though 

 some had as many as 160. Mummy wheat has been observed 

 with ears containing nearly a dozen branches. There are 150 

 grains in one ear, and as many as 60 ears from one seed. 

 Wheat has the advantage of extreme diminution of the number 

 of seeds to each flower, giving richness in starch and gluten, 

 combined with the advantage of numerous flowers on each 

 plant, giving many seeds. 



The Wheat Kernel is a dry, indehiscent, unilocular caryopsis. 

 It is oval in shape, and has the appearance of being folded up- 

 on itself from two sides. A ventral crease marks the coming 

 together of the two folds. At the base 

 of the berry opposite the crease is 

 found the embryo, germ, or chit. At the 

 apex is a collection of minute hairs. The 

 entire grain fills from 20 to 30 cubic 

 millimeters of space, of which at least 

 thirteen-fourteenths are occupied with 

 the starchy endosperm. The latter al- 

 most surrounds the embryo, and its cells 

 are very irregularly shaped. The em- 

 bryo is composed of the absorbent organ 

 (scutellum), and the miniature first 

 leaves and roots. It forms about 6 per 

 cent of the wheat kernel. 



The endosperm and embryo are flom- 

 rletely enclosed by a single layer of |[uten cells j 

 aleurone or gluten cells. The weight of bran ; / and a, outer coats of 

 this layer is 8 per cent of that of the "ran ; ft, epidermis of kernel, 

 whole grain. The next covering is a single layer of collapsed 

 cells, known as the tegmen. This is again surrounded by a 

 third envelope, the testa, or episperm, which contains the 

 greater part of the coloring matter of the grain. This coloring 

 matter is of two kinds, one a palish yellow, and the other an 

 orange yellow, and the degree in which one or the other pre- 

 dominates determines whether the wheat is known as white, 

 yellow or red. The three layers just described constitute the 

 envelope of the seed proper. They in turn are again inclosed 



