Agronomy and Horticulture Department


Date of this Version



The American Naturalist, Vol. 46, No. 550 (Oct., 1912), pp. 612-615


Copyright 1912 R. A. Emerson


Before the Mendelian methods of analysis became available, considerable wonder would doubtless have been excited by the "mysterious" appearance in F2 of one colored grain-purple or red-to every five or six white ones in case of a maize cross, both parents and F, of which had only white grains. An occurrence of this sort has recently been noted in one of my maize cultures and the F2 numbers are explained here as a trihybrid or tetrahybrid ratio. The crosses in question were made primarily for a study of size inheritance and fairly large numbers have been grown. The varieties concerned are two dwarfs of distinctly different types, Tom Thumb pop and California Rice pop, and a tall type Missouri dent. The facts with reference to aleurone color are these: Tom Thumb pop, a "white" corn (i. e., having non-colored aleurone), was crossed with Missouri dent, also a white corn. Three generations of hybrid plants four generations for aleurone and other endosperm characters- have been grown without the appearance of any but white grains. The same white-seeded Missouri dent was also crossed with the white-seeded California pop. The three hybrid generations grown to date have shown no aleurone color. Furthermore, when the same white Tom Thumb pop was crossed with the same white California pop, only white grains appeared in F,. But both of the two ears containing F2 seeds-the only ones that have been produced as yet-had a sprinkling of both purple and red grains, too many to be explained as due to care- less guarding against foreign pollen and too few to be accounted for by any simple monohybrid or dihybrid formula