1 66 TEXTBOOK OF BOTANY 



the later leaves can push on beyond it. This first secondary 

 leaf remains small and forms almost no blade (Fig. 103, E). 

 The next forms a small blade ; and each later leaf, as it 

 grows and opens, becomes larger than the preceding one, 

 until finally the size of leaf is reached that is characteristic 

 of the mature plant. Meanwhile the plumule has grown into 

 an erect stem, on which the leaves are borne. The seed 

 leaf remains within the kernel. It absorbs the food that is 

 stored in the endosperm and passes this food on to the other 

 parts of the seedling (radicle, plumule, and secondary leaves). 

 After the food supply of the endosperm is used up, the seed 

 leaf is no longer useful, and it soon dies. The seed leaf of 

 the com, therefore, never becomes a green foliage leaf. 



188. Varieties of Com. — Many varieties of Indian com are in 

 cultivation, but all of them seem to have been developed from a single 

 species, Zea Mays. In 1899, a list was made of 507 varieties, divided 

 among the following groups : pop corns, flint corns, dent corns, soft 

 corns, and sweet corns. The flint corns, the dent corns, and the few 

 varieties of soft com that are cultivated are usually spoken of as 

 " field com." In addition to the five classes above named, two others 

 are known. These are the pod corns, little grown except as curiosities, 

 each of whose kernels is enclosed in a separate pod formed by a growth 

 of some of the surrounding bracts ; and the starchy-sweet corns, which 

 are cultivated by certain Indian tribes. 



189. Relatives of the Corn. — The Indian corn is a member of the 

 grass family, whose 3500 species include all the wild and cultivated 

 grasses, the bamboos, sugar cane, sorghum, broom corn, and the cereal 

 grains (including, besides Indian com, rice, wheat, barley, rye, oats, 

 and millet). The closest known relative of Indian com is teosinte. 

 This is a native of Mexico, but it is raised as a fodder plant in many 

 warm countries. It is much like Indian corn, excepting that its clusters 

 of pistillate flowers are smaller and simpler than com ears. It is 

 thought by some that Indian com may have originated long ago as a 

 variety of teosinte; and that this new variety was found valuable 

 by the Indians, who began to ciiltivate it. 



190. Historical Note. — Indian com is not now known to grow 

 anywhere as a wild plant, excepting that now and then it escapes from 

 cultivation and lives wild for a few generations. Its original home 

 was on the American continent, probably in Mexico. It was widely 



