62 SEEDS AND FRUITS 



tifically called a cariopsis, a term which refers to, its nut-like char- 

 acter. 



The seed itself contains three distinct parts, embryo, endo- 

 sperm, and seed coat. The seed coat, however, since it is covered 

 by the ovary wall which performs the protective function of an 

 ordinary seed coat, is poorly developed and so closely joined 

 with the ovary wall that it appears to be a part of its structure. 

 In containing three distinct parts, embryo, endosperm, and seed 

 coat, it is seen that the seeds of the Grass type are identical with 

 those of the Flax and Buckwheat type: but in possessing only 

 one cotyledon instead of two, they are clearly distinguished 

 from both of the other types. 



In external features, the seeds of the Grasses present many 

 variations, though probably not so many as occur among some 

 other types of seeds. Most of them are small, but various sizes, 

 ranging from that of a Timothy seed and even smaller up to 

 that of a Corn kernel occur. In most cases they are elongated, 

 and have a groove on one side. In most varieties of Oats and 

 Barley, and in many of the Grasses having very small seeds, the 

 cariopsis remains enveloped by the palea and flowering glume, in 

 which case the entire structure may have the appearance of a 

 seed, especially when the barbed awns and other structures devel- 

 oped by the flowering glume function in dissemination. The 

 seeds of most Grasses are white, gray, yellow or brown, but in 

 Corn such colors as red, blue, purple, and black often occur. 



The seeds of those Grasses known as the grains are our chief 

 source of food. Although all of the grains contain practically 

 the same food elements, they differ in the proportion of the differ* 

 ent elements and consequently are fitted for different uses. Even 

 within a seed, various structures differ so much in composition 

 that they are adapted to special uses as is well shown in the 

 milling of Wheat. Likewise in case of Corn, the oil and protein 

 contents are so closely related to structure that one can judge the 

 relative proportion of these substances by observing the relative 

 sizes of certain structures of the kernel. 



Com Kernel. — A study of a section through a kernel of corn, 

 as shown in Figure 66, will give a notion of the general structure 

 of the Grass type of seeds. Notice that within the covering (o) 

 there are two distinct regions, that to the right and below being 

 the embryo, and that to the left and above being the endosperm. 



