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.