2. Races of Maize. Cutler's collections of Mexican and Guatemalan maize have made it possible to begin another long-time project, the determination and description of the races of maize. While Sturtevant's classification (dents, flints, pops, etc.) is adequate as a cataloguing device there is also need for at least a rough grouping indicating general relationships in somewhat the same way that anthropologists analyze human variation. For such a grouping it is necessary to know as much as possible about the entire plant; tassel and leaf as well as ear and grain. We have therefore built up an herbarium of as many corn varieties as possible, including with the ear, herbarium specimens of seedlings, leaves, and tassels and notes on the number of nodes above the ear, the height of the plant, etc. For a considerable number of our collections duplicate specimens have been prepared in St. Louis, Texas, and Cuba. In addition to Cutler's collections we grew George Carter's extensive collection of Indian varieties from the southwest and a few unusual varieties such as Louisiana Gourdseed.
From an examination of the herbarium material the following characters were chosen as most indicative of general relationship: row number; kernel width, length, and thickness; mid cob width; number of tassel branches; length of glume (tassel); percentage of condensed internodes in tassel; pedicel length of pedicillate spikelet; percentage of sub-sessile pedicillate spikelets; length of sterile zone at base of tassel branches; pubescence of sheath.
By the use of these criteria our Mexican and Guatemalan collections can be divided into at least three main races, Big Grains, Mexican Pyramidals, and small-seeded Tropical Flints. The Big Grains are big cobbed and big kerneled with more or less enlarged butts. While they may be flour or flint they are characteristically more or less dented. The small-seeded Tropical Flints are not only exceedingly straight-rowed but the kernels are very uniform in diameter so that a row of them looks like a stack of pearl buttons seen from the side. They are all flints, have small cylindrical ears, and are prevailingly bright-colored. The Mexican Pyramidals are the common race in Mexico City and adjacent portions of the plateau. Important to U.S. corn breeding because most of their distinguishing features, in a more or less diluted form, are found in cornbelt dents. They have a short pyramidal ear with long (often pointed) kernels. They are nearly all dents or semidents and the majority of them are white. They have few tassel branches and large glumes so that they are strikingly different from most other races and have been commented upon by Bonafous and Bukasov. The Indian corns of the southwest go into two races, the Pima-Papago and the Pueblo, the latter being closely allied to the Big Grains. Median values for representatives of these five races (and subraces) in our collections are as follows:
|No. of tassel branches||20||21||18||10||4|
|Length of sterile zone||8||7||8||5||3|
|Percent condensed internodes||0||0||10||0||40|
|Percent sub-sessile spikelets||0||0||0||10||50|
It will be seen that on the whole the Big Grains are at one extreme and the Mexican Pyramidals are at the other. It is also to be noted that the Pima-Papago race while similar to the Tropical Flints in cob-size and grain-size is far removed from them in all other characters. Collins (in Guernsey and Kidder 1921) was therefore in error in identifying the prehistoric Basketmaker corn (which is practically identical with the modern Pima-Papago) with the Tropical Flints.