36 BULLETIN 754, U. S. DEPARTMENT OF AGRICULTURE. 
The deviation of 4.45 times the probable error above the expected 
percentage for the total number of seeds, together with the large 
proportion of ears having an excess of white seeds, indicates a rather 
definite tendency toward a higher percentage of the recessive class 
than that called for by the Mendelian theory. 
The inclination is to attribute such a small variation to a failure 
to properly classify the seeds, so that some faintly colored seeds were 
being included with the white seeds. The number of individuals 
necessary to detect such a slight error would be very large, so that 
the number of second-generation ears obtained is not sufficient to 
shed light on this matter. 
COMPOSITION IN THE SECOND GENERATION OF THE HYBRID 
DH 237. 
An examination of the zygotic formule for the hybrid Dh 237 will 
show that two equal groups of plants are to be expected in this 
hybrid—one group homozygous for the color factor # and heterozy- 
gous for the factor C, the other group being heterozygous for both 
of these factors. Representatives of both groups were obtained, 8 
plants exhibiting a dihybrid and 19 plants a monohybrid ratio of 
white to colored seeds. Although these two ratios were expected in 
equal numbers, the deviation of 5 plants below the expected for the 
dihybrid ratio may be looked upon as a chance fluctuation. 
In tabulating the plants, only 23 are shown in Tables XVI and ° 
XVII, as four plants, owing to the nature of the pollinations, pro- 
duced all-colored ears only and were not tabulated. It will be re- 
called that all of the plants of the hybrid Dh 234 were alike in that 
they were homozygous for the factor @ and heterozygous for the 
factor f. 
. Two groups of ears are to be expected in crossing these two hy- 
brids: One group all colored, the result of crossing the plants of 
Dh 237 constituted cC RR with Dh 234 CC Rr; the other group with 
a monohybrid ratio of white to colored seeds, the result of crossing 
plants of Dh 237 constituted Ce Rr with Dh 234 CO Rr. In both 
cases self-pollinating plants of the hybrid Dh 234 show ears with a 
monohybrid ratio. In the first instance self-pollinated plants of the 
hybrid Dh 237 should also result in ears with monohybrid ratios and 
in the second instance in dihybrid ratios of white to colored seeds. » 
With this expectation it becomes possible to separate the plants of 
the hybrid Dh 237 when they were both crossed with the hybrid Dh 
234 into two classes, one of which contains plants heterozygous for 
two color factors and the other with plants homozygous for one and 
heterozygous for the other factor. 
Only four plants of the progeny of the hybrid Dh 237 were ob- 
served to have a dihybrid ratio of white to colored seeds. These are 
shown in Table XVII, However, an examination of Table XVI re- 
