9. It has been observed by many investigators that the F1 ears of maize-teosinte hybrids are 4-rowed (paired spikelets, two-ranked). This indicates that the paired spikelet condition of the maize ear is dominant to the single spikelets of teosinte. Collins and Kempton, 1920, showed that in an F2 population, paired and single spikelets segregated 3:1. Data obtained by the writer in the summer of 1937 have confirmed their findings.
It has not been pointed out, however, that the two-ranked condition of teosinte, which appears in the F1 of maize-teosinte hybrids, segregates as a unit character in the F2 population. The combined 3:1 segregation of the dominant two-ranked condition of teosinte (as contrasted with the many-ranked condition of maize) and the 3:1 segregation of paired vs single spikelets, gave a 9:3:3:1 ratio, indicating that these two genes are independent of each other. This independence makes possible the combination of the recessive many-ranked condition of maize with the recessive single spikelets of teosinte, giving two kinds of ears: some with an even number of rows and others with an odd number of rows. Thus, 3-, 4-, and 5-rowed ears with single spikelets have been found. With paired spikelets these would presumably have been 6-, 8-, and 10-rowed ears, respectively.