3. Differential dominance in number of kernel rows. - In the 1940 News Letter (14: 19-21), I reported differences in relative dominance of ten inbred lines of 12-row maize and of two 8-row inbred lines in crosses F₃ and F₄ cultures of the cross W-W × C-R of 12-row with 8-row lines. I now present further data on the crosses previously reported and tests of a few inbred lines not represented in the earlier report. The accompanying table includes the earlier as well as the later data.

Number of individuals and mean row number of F₁ crosses
of 8-row with 12-row inbreds

Key to line designations:

Of the 8-row inbreds, Sanford White and Yellow Flour are somewhat more nearly dominant even than Luce's Favorite, while Yellow Flint and Red Flint are less nearly recessive than Golden Bantam. Similar differences are shown by different 12-row lines. Such differences are well illustrated by the following frequency distributions for number of kernel rows in crosses of two 12-row with two 8-row lines:-

That these differences in behavior are conditioned by gene differences rather than by cytoplasmic diversity is indicated by the fact that reciprocal crosses are essentially alike. The following data from reciprocal crosses are all that are now available:

It is not surprising that 12-row lines exhibit differences in relative dominance, because several of them at least are known to have different row-number genotypes. But 8-row types have been assumed to have the same genotype for number of kernel rows. Negative evidence in support of this notion is (1) Crosses of 8-row inbreds have not resulted, in my experience, in the production of other than 8-row types. (2) Crosses of 8-row with 12-row inbreds have not resulted in types with more than 12 kernel rows. It is, of course, conceivable that genes responsible for the 8-row condition may be alleles with the same effect on row number but with somewhat different dominance behavior.