72 BULLETIN 754, U. S. DEPARTMENT OF AGRICULTURE. 
had approximately 43.75 per cent white seeds, indicating that the 
plants in question were heterozygous for both color factors C and R. 
If the correlations were independent of the gametic composition, 
we might expect no consistent differences in the degree of correlation 
between the monohybrid and dihybrid ears; but if, on the contrary, 
the correlation is between a factor for color and endosperm texture, 
the correlation should be reduced in a definite degree on the dihybrid 
ears. The reason for this reduction in the degree of correlation 
follows. 
A plant which when self-pollinated produces an ear with a di- 
hybrid ratio of colored to white seeds and a monohybrid ratio of 
horny to waxy seeds must be heterozygous for both color factors 
and endosperm texture. 
If we assume that the association is between a color factor C and 
horny endosperm /, and if we further assume that the association 
results in the combination CH being formed three times as often 
as the combination CA, we then have the above plant. making the 
following gametic classes: 3 CRH, 1 CRh, 3 CrH, 1 Crh, 1 cRH, 
3 cRh, 1 crH, and 3 crh. 
The union of the gametes CrH and cr will result in a white horny 
zygote; and since C’ and H are the associated factors, these seeds 
will be produced in relatively large numbers, resulting in a reduc- 
tion in the degree of correlation between colored aleurone and horny 
endosperm. 7 
A plant which when self-pollinated produces an ear with a mono- 
hybrid ratio of white to colored seeds, as well as a monohybrid ratio 
of horny to waxy seeds, must be homozygous for one color factor and 
heterozygous for the other color factor as well as endosperm texture. 
If we assume the heterozygous color factor to be the one which is 
associated with endosperm texture, we have the above plant making 
the following gametic classes: 3 CRH, 1 CRA, 1 cRH, and 3 ch. 
The union of gametes CRH with cRH results in a colored horny 
zygote. 
Thus every gamete carrying the color factor C results in a colored 
zygote, and the correlation is the same as if it were between color 
and texture rather than a factor for color and texture, and the nor- 
mal 41-7-7-9 zygotic grouping is expected, and the correlation be- 
tween colored aleurone and horny endosperm is 0.766. 
When the dihybrid ratio of white to colored seeds is obtained, all 
of the gametes bearing the factor for color C do not result in colored 
seeds, and the zygotic classes are altered from the above 41—7—7-9 
to 123-21-69-48 and the correlation is reduced from 0.766 to 0.570. 
From the hybrid Dh 237 four self-pollinated ears were obtained 
that had the percentage of white seeds closely approximating 43.75, 
