The Inheritance of Quantitative Characters in Maize 9 
complications. In one of these crosses between a black glumed 
and a white glumed race, however, the F 2 generation was 630 
black : 40 white, clearly a ratio of 15 black : 1 white. Here 
there appeared to be two factors for black, each dominant to its 
own absence, segregating and recombining independently. The 
zygotic formula of the black race may be expressed as B X B X B 2 B 2 
and that of the white race as bji^j).^ The F x generation brings 
both of these factors to the heterozygous condition, B x b x B 2 b 2j and 
in F 2 gives 9B X B 2 : 3B x b 2 : Sb t B 2 : lbj> 2 . But as the first three 
classes are alike in appearance, the ratio of F 2 is 15 black : 1 
white. 
Again, experimenting with wheat. Xilsson-Ehle found a di- 
hybrid Mendelian ratio. A brown headed wheat crossed with a 
white headed variety gaye in F 2 1410 brown headed plants to 94 
white headed plants, a ratio exactly 15 : 1. There is hardly a 
doubt that the brown headed variety had the formula B X B X B 2 B 2 
and the white headed variety the formula b x b x b 2 b 2 . The proof of 
the interpretation comes from a more surprising experiment of 
the same investigator. 
He made six crosses between a red-seeded wheat and a white- 
seeded variety. The F x plants were all red-seeded : the 384 
plants of the F 2 generation were also red-seeded. This result 
was so peculiar that selfed seed of all of the 78 F 2 plants of one 
cross were grown and the progeny of each recorded in the F 3 
generation. This result was obtained : 
50 F 2 plants gave only red-seeded plants. 
8 F 2 plants gave approximately 3 red : 1 white plants. 
15 F 2 plants gave approximately 15 red : 1 white plants. 
5 F 2 plants gave approximately 63 red : 1 white plants. 
The interpretation of this result was that a trihybrid had been 
produced by crossing R^R X R 2 R 2 R^R ? with r x r x r 2 r 2 r 3 r s , each R 
factor being able to produce the red color in the seed, but segre- 
gating with its own absence independently of the other factors. 
The red F a generation would have the formula R^R^B^ and 
should by recombination produce 63 red : 1 white plants in F 2 . 
To be sure, no white-seeded plants were obtained in the 384 in- 
dividuals forming the total F 2 generation, but such a result might 
be expected frequently in chance matings of this type following 
the Law of Error, unless more F 2 progeny were grown. The 
real proof of the interpretation comes from the F 3 generation as 
noted before. The F 2 generation, theoretically, consists of 63 reds 
to 1 white. The 63 red plants, tho similar in appearance, should 
have tbe different zygotic formulae expected of an ordinary tri- 
