182 BREEDING CROP PLANTS 



organs. These various abnormalities tend to support the 

 hypothesis outlined by Montgomery. 



Collins (1912) has supported the hypothesis that maize 

 originated as a hybrid between teosinte and an unknown grass 

 belonging to the tribe Andropogonese. This grass is believed to 

 be somewhat like some varieties of pod corn (Zea mays tunicata) 

 which produce seeds only in the tassel and are in many essen- 

 tial characters strongly contrasted with teosinte. These conclu- 

 sions have been reached after extensive studies of many primitive 

 varieties of maize, teosinte, and hybrids between teosinte and 

 maize. Collins especially emphasizes the fact that ' ' in practically 

 every case where there is pronounced divergence between teosinte 

 and pod corn, maize shows characters of an intermediate nature 

 and these characters are usually variable." 



Kuwada (1919, abstract by Ikeno, 1920) has published cyto- 

 logical support for this theory. He finds the chromosomes of 

 maize to be of two types, long and short. He also finds that 

 Euchlaena has 10 haploid chromosomes which are long, and 

 Andropogon likewise has the same number of haploid chromo- 

 somes which are distinguished by their shortness. 



Sturtevant (1899) divided the species Zea mays into several 

 groups and considered each of specific rank. The more common 

 practice is to make the five major groups sub-species, retaining 

 the monotypic species Zea mays. This plan was followed by 

 East (see East and Hayes, 1911). A short description of the 

 differential characters of these five groups is given here. 



Zea mays tunicata, the pod corns, Sturtevant, Bulletin Torrey 

 Botanical Club, 1894, page 355. 



"In this group each kernel is enclosed in a pod or husks, and 

 the ear thus formed is enclosed in husks." This is perhaps the 

 least deserving of sub-specific rank as it is an unfixable group 

 (seepage 189). 



Zea mays indurata, the flint corns, Sturtevant, Bulletin Torrey 

 Botanical Club, 1894, page 355. 



The group comprises those varieties with a starchy endosperm 

 in which the soft starch is surrounded by corneous starch. The 

 proportions of soft and corneous starch vary considerably in 

 different varieties. 



Zea mays everta, the pop corns. Sturtevant, Bulletin Torrey 

 Botanical Club, 1894, page 325. 



In this group there is only a small proportion of soft starch 



