46 BULLETIN 754, U. S. DEPARTMENT OF AGRICULTURE. 
progeny of the hybrid Dh 234. The fact that male gametes bearing 
colorless aleurone are below the expected would seem to indicate 
that the gametes bearing recessive characters are less vigorous than 
those bearing the dominant characters. The observed differences 
could also be explained by assuming the plant to be making an un- 
equal proportion of male gametes bearing colored and colorless 
aleurone. / 
As the result of ‘self-pollinating plants grown from the hetero- 
zygous colored seeds of ears Nos. 1099 and 1111, 24 ears were ob- 
tained. These ears are shown in Table XIX. 
The expected percentage of white seeds is 25 and the observed 25.6. 
The deviation in this case is only 2.3 times the probable error. Only 
one ear deviated from the expected percentage by more than three 
times the probable error, all the ears showing a remarkable uni- 
formity. 
Reciprocal crosses between heterozygous colored plants and homo- 
zygous white plants showed that for the heterozygous colored plants 
the male gametes bearing colorless aleurone were 3 per cent below - 
the expected proportion. These same crosses showed the female 
gametes to be approximately normal. From these facts it would be 
expected that self-pollinating these heterozygous colored plants 
would result in ears having approximately 23.5 per cent white. The 
observed percentage of 25.6 can not be considered as a chance devia- 
tion from 23.5 per cent, since the deviation of 2.1 per cent is 8.1 times 
the probable error. 
To explain these conflicting results it is necessary to make the as- 
sumption that the gametes bearing the recessive color find a better 
medium for growth in the stigmas of the heterozygous plant than in 
those of the homozygous white plants. An adequate test of this as- 
sumption would require numbers in excess of 10,000, making it very 
unlikely that the hypothesis will soon be put to the test. 
COMPOSITION IN THE THIRD GENERATION OF THE HYBRID DH 237. 
Four ears from the hybrid Dh 237 were selected for planting. Two 
of the four ears are shown in Table XVII as Nos. 1129 and 1130. The 
other two ears were the result of crossing Dh 237 by Dh 284, and 
since all the seeds were colored on both these latter ears, they do 
not appear in Table XVI. Their progeny are discussed later with 
the progeny of a similar ear from the hybrid Dh 234. 
Ear No. 1129, grown in 1918, was the result of self-pollinating a 
plant of the hybrid Dh 237. This ear had 747 seeds with 25.1 per 
cent white, the percentage being almost exactly the expected 25 
per cent. Since this ear is demonstrated to be segregating in a 
normal monohybrid ratio, the progeny plants of the heterozygous 
seeds are expected to behave in a like manner. 
