Dull endosperm, du, which intensifies suam and su1 (see Corn Letter of March 23, 1937, p. 13) has no distinctly visible effect on su2

2. Dull endosperm, du, which intensifies su^am and su₁ (see Corn Letter of March 23, 1937, p. 13) has no distinctly visible effect on su₂. Three separate crosses of du x su₂ were made and F₁s selfed. Six ears from each F₂ showed no definite effect of du on su₂. Any such effect is very slight if existent at all. Therefore, the mechanisms by which the su₁ and su₂ genes act must be different, at least in part.