3. The inheritance of yellow endosperm color is more complex than has been generally believed. Evidence is available for the presence of at least one gene in addition to Y₁ and Y₃ which is concerned with the presence or absence of yellow endosperm pigment. Ratios of 3:1, 9:7, 15:1, 45:19 and others possibly more complex have been obtained.

The yellow scutellum gene sy is able to produce its effect in the presence of y₁y₁, but in the presence of other recessive whites the development of pigment (carotin) is completely suppressed. The factor or factors involved have not been completely identified.

G. F. Sprague