CEREALS AND FORAGE PLANTS 



349 



failed to germinate, or some of the seedlings are decidedly 

 weaker than the others, that ear should be discarded. 



The germination of corn is illustrated in Figs. 21-27. In 

 Fig. 21 is shown a section of a grain of corn. Within the 

 testa, the contents are divided into two principal regions, that 

 to the right and below being the embryo, 

 and that to the left and above, the endo- 

 sperm, in which the food is stored. The 

 position of the embryo is peculiar, for in- 

 stead of being surrounded by the endo- 

 sperm, it lies to one side of it. It will be 

 noticed that the single large cotyledon of 

 the embryo is in contact with the endo- 

 sperm, from which it obtains food which it 

 passes on to the growing parts that are to 

 escape from the seed. In the embryo may 

 also be seen the bud that is to produce 

 the stem and leaves, and below it the 

 hypocotyl that is to escape first and estab- 

 lish the root system. The cotyledon is 

 attached at the joint which separates the 

 young stem and the hypocotyl. The figure 

 also indicates that the endosperm has two 

 regions : the outer region (more deeply 

 shaded) is the " horny endosperm," which 

 contains protein food in addition to its 

 starch ; while the inner region (with lighter 

 shading) is the " starchy endosperm." As the relative size of 

 the two regions varies, the richness of the grain in protein 

 or in starch varies. Figures 22 and 23 are slightly different 

 views of a sprouting grain, showing the superficial position of 

 the embryo, and that it simply splits a membrane (the testa) 

 to be completely exposed. Figures 24-26 are all in the same 

 position, Fig. 24 showing the tip of the hypocotyl turning 

 towards the ground ; Fig. 25 showing the great elongation of 



FIGS. 22 and 23. Two 

 views of sprouting 

 grains of corn, show- 

 ing the relation of 

 the embryo to the 

 food supply ; the 

 "sprout" is the tip 

 of the hypocotyl. 



