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