THE INDIAN CORN 



165 



end of the kernel, the horny endosperm being present only 

 on the sides. The starchy endosperm loses water and 

 shrinks as the kernel ripens, so that the outer end of the 

 kernel is indented. The endosperm of a pop corn is entirely 

 or almost entirely horny. It is the expansion of water within 

 the horny endosperm when the kernel is heated that causes 

 an explosion or " popping " of the corn. The endosperm of 

 sweet corns contains a large proportion of sugar and relatively 

 little starch ; the kernels lose much water as they ripen, and 

 so become wrinkled. 



187. Germination. In most respects the germination of 

 the corn kernel is much like that of the squash seed. The 

 radicle breaks 

 through the seed 

 leaf, the seed coat, 

 and the fruit coat, 

 and then bends, 

 if necessary, so as 

 to grow down- 

 ward into the soil 

 (Pig. 103, A, B). 

 The plumule also 

 breaks its way 

 out and grows 

 upward. At this 

 time, the plumule 

 and the smaller 

 secondary leaves 

 are surrounded 

 by the first sec- 

 ondary leaf , which 

 is so wrapped 

 about the plumule as to make a pointed structure with a hard, 

 sharp point that pushes through the soil. In time the pro- 

 tecting secondary leaf unrolls slightly, so that the plumule with 



FIG. 103. A, B, two views of a germinating 

 kernel of Indian corn. C, D, E, stages in the de- 

 velopment of a corn seedling ; notice the points at 

 which secondary roots arise. 



