PHYSIOLOGY OF THE CORN PLANT 



171 



black Mexican or Cuzco varieties of corn, in which the 

 aleurone layer of the grain is bluish-black, is placed on 

 the silks of white or yellow varieties, many of the kernels 

 developing will show the bluish-black color. Also if the 

 silks of sweet corn receive pollen from Flint and Dent 

 varieties many of the kernels produced as a result of this 

 immediate cross wUl 

 possess the character- 

 istic endosperms of 

 the parent plants. 

 Such &st-generation 

 changes in the charac- 

 ter of, the endosperm 

 as have just been cited 

 constitute the phe- 

 nomenon known as 

 xenia. 



214. Development 

 of the ear. — When 

 the ear has developed 

 to the stage at which 

 fertilization takes 

 place, it consists of a 

 spike (the cob) bear- 

 ing the pistillate flowers in even numbered rows, and the 

 covering or husk. The development of the kernels after 

 fertilization takes place completes the formation of the ear. 

 The silks at the butt of the ear develop and are polUnated 

 first, followed In succession by those at the middle and 

 finally at the tip of the ear. For this reason the basal 

 kernels develop somewhat in advance of the middle and 

 tip kernels. Each developing kernel is fed by a single 

 fibro-vascular bundle which extends from the stem between 



Fig. 28. — Cross-section of corn ear look- 

 ing toward the base: s, inner surface of 

 upper thick glume seen behind the thin 

 glume and palets; S, outer surface of 

 lower thick glume; F, axes; T, denser 

 portion of woody zone; H, depression; 

 B, zone with fibro-vascular bundles; 

 M, pith. 



