32 BULLETIN 754, U. S. DEPARTMENT OF AGRICULTURE. 
GAMETIC COMPOSITION OF THE TWO HYBRIDS DH 234 AND DH 237. 
The percentage of white seeds obtained in the second generation 
of the hybrid Dh 234 showed that the aleurone color of this hybrid 
was behaving as a unit character, all the ears approximating 25 per 
cent white. The second-generation plants of the hybrid Dh 237 fell 
into two main groups, approximately half of the plants having a 
monohybrid and the other half a dihybrid ratio of white to colored 
seeds, 
When the two hybrids were crossed, two classes of ears resulted— 
one group all colored, the other group having the monohybrid ratio | 
of white to colored seeds. To explain these phenomena, it becomes 
necessary to assume that aleurone color is the result of two factors. 
The hybrid Dh 234, all the plants of which, when self-pollinated or 
crossed with sister plants, resulted in ears with a monohybrid ratio 
of white to colored seeds, must have been homozygous for one color 
factor and heterozygous for the other. The plants of Dh 237 which 
when self-pollinated produced ears with a monohybrid ratio of white 
seeds were also heterozygous for one color factor and homozygous for 
the other. 
Crosses between plants of this type with plants of the hybrid Dh 
234 resulted in ears all the seeds of which were colored, indicating 
that the factor homozygous in Dh 234 was heterozygous in Dh 237. 
Since one-half of the plants of the hybrid Dh 237 when self-polli- 
nated or crossed with sister plants produced ears with a dihybrid 
ratio of white and colored seeds, these plants must be heterozygous 
for both color factors. Crosses between plants of this nature and — 
plants of the hybrid Dh 234 resulted in ears with a monohybrid ratio 
of white to colored seeds. 
It will be recalled that self-pollinating plants of the hybrid Dh 
237 resulted in two approximately equal classes of ears, one with a 
monohybrid ratio of white to colored seeds and one with a dihybrid 
ratio of white to colored seeds. The hybrid Dh 234 when self- 
pollinated produced only ears with a monohybrid ratio, but when 
crossed with plants of the hybrid Dh 237 two classes of ears again 
resulted, one class having all the seeds colored, while an equal 
number had a monohybrid ratio of white to colored seeds. 
To explain the two classes of ears resulting from self-pollinating 
first-generation plants of the hybrid Dh 237 and at the same time 
to explain the results obtained when first-generation plants of the 
hybrid Dh 237 were crossed with first-generation plants of the hy- 
brid Dh 234, it is necessary to assume somewhat involved gametic 
formule. 
It is assumed that in the first cross (Dh 237) the Chinese parent 
had the gametic combination cP cP and the Algeria CR Cr, where 
