1. In tetraploid maize unimodal curves were obtained from hybrids between self-fertile and self-sterile lines back-crossed to the self-fertile parent; in the back-cross to the self-sterile parent a bimodal ourve was obtained, 250 or more individuals being involved in each population. In the F₂ population of the same crosses unimodal or very weakly bimodal curves were obtained.

The F₁ of the incompatible matings between the self compatible lines (B lg and su) of tetraploid maize reported in the last News Letter was found to be self-fertile, and the back-crosses to the parent lines were also compatible, as indicated by observations on 50 or more ears from each cross. An incompatible mating between the cross-sterile B Lg line and a self-sterile B line showed an intermediate degree of self-fertility (37%) in F₁. The backcross to the B lg parent was 37% compatible (28 ears) while the back-cross to the B Lg parent was only 15 percent compatible.

Harold E. Fischer