Two pure lines of Cucurbita pepo, both approximately spherical in shape, produce when crossed an F1 in which the fruits are much flattened as in the typical "disc" form. The F2 of this cross gave approximately 9 disc : 6 spherical: 1 elongate fruits, results suggesting a dihybrid condition, the dominant allelomorph tending in each case to flatten the shape of the fruit, and the recessive to elongate it; and that their effects are cumulative. Each parental sphere has one of the dominant factors (Ab) and (aB); the F1 and the discs in the F2 have both of them (AB); the elongate individuals have neither (ab). This hypothesis offers a simple explanation of the F2 segregation, of the results obtained by back-crosses of the F1 on both parent types, and of the character of the F3. Evidence is presented that in addition to these 2 major flattening factors there are a number of minor ones, much less pronounced in their effect and inherited independently of the major ones. Factors inhibiting the flattening effect also probably occur. The conclusion is justified that shape factors, controlling growth correlations, exist in this material and that they are inherited in typical Mendelian fashion.