MAIZE 



MAIZE 



401 







Fig. 603. Hopi com grown by tlie Pueblo Indians. (From specimens iu the United 



States National Musenm.) 



are produced in very great numbers, as many as 

 18,000,000 by a single plant. The pollen begins to 

 be shed one to three days before the silk emerges 

 from between the husks, and continues to fall for 

 eight days, more or less, although the silk is pol- 

 lenized usually on the first day of its appearance. 

 The egg apparatus in the ovule of maize consists 

 of three cells, and in the center of the embryo-sac 

 is an endosperm nucleus. The fertilization of the 

 egg cell results in the formation of the corn em- 

 bryo, while the double fertilization of the endo- 

 sperm nucleus -by the second sperm nucleus pro- 

 duces an immediate effect on the color of the 

 reserve food stored about the embryo. This imme- 

 diate effect of the pollen on the offspring kernels 

 is called xenia. 



Fig. 60S. The sexes ; pistil- 

 late spike or ear, stami- 

 nate panicle or tassel. 



B26 



Fig . 606 . Ears too high on tlie 

 left; ontlieriglit.earswell 

 placed. 



Kernels. — The caryopses or 

 kernels of corn (Fig. 596), re- 

 sulting from the act of fertili- 

 zation, are arranged in even- 

 numbered rows on the fleshy 

 axis, or cob, surrounded by the 

 husk. Each husk represents the 

 sheathing leaf base and the 

 outer ones are usually tipped by 

 a green, rudimentary leaf-blade, 

 which occasionally displays a 

 ligule. The outer, innermost husk 

 is two -keeled, like a sled with 

 runners, and thus it accommo- 

 dates itself to the flattened or 

 hollowed -out stem surface. 

 Occasionally smaller ears are 

 enclosed by the outer husks, so 

 that the ear together with the 

 husks is to be regarded as a 

 short, axillary, branch bearing 

 reduced leaves and flowers. 



Each caryopsis has two distinct coats, viz., the 

 ovarian wall and the seed-coats. On microscopic 

 section, the cell layers composing the ovarian wall, 

 or pericarp, and the extremely thin seed-coats are 

 distinctly visible. The reserve food in corn is horny 

 proteinaceous material and mealy starch, while 

 the embryo itself contains the largest amount of 

 oil. The proteinaceous and starchy reserve foods 

 comprise the albumen, which touches the embryo 

 on the whole of one side, where the scutellum is 

 found. The corn embryo, chit or germ, consists of 

 the radicle surrounded by a root-sheath, or coleo- 

 rhiza, a short hypocotyl from which arises the suck- 

 ing organ, or scutellum, and a single cotyledon 

 that surrounds several tightly-rolled plumular 

 leaves. The epidermal cells of the scutellum 

 secrete an enzyme which transforms the reserve 

 food into a usable form when the embryo begins to 

 grow. 



In germination, the radicle protrudes first by 



Fig. 604. 

 Squaw com grown 

 In Manitoba. Sec- 

 tion at a shown 

 below. 



