Hayes and Garber - Cucurbit Breeding

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 tunicatd)
which produce seeds only in the tassel and are in many essential
characters strongly contrasted with teosinte.
These conclusions
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 ' l 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 cytological
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 chromosomes
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