INHERITANCE OF ENDOSPERM COLOR IN MAIZE 405 
have the formula aayy, neither the suppression nor the pigment factor 
being present. 
First generation (Fi) progeny from crosses between whites such 
as 1X4, or whites and yellows such as 2 X 3, should give, when 
backcrossed with white endosperm aayy (4) plants, white and yellow 
endosperm seeds in the ratio of 3 W : i Y. In other words, two whites 
crossed together in Fi give a certain proportion of yellows. The 
obtaining of such results in partially worked out experiments on 
heredity of endosperm color, in which it was taken for granted that 
white endosperm color was always recessive, might be temporarily 
interpreted as due to the presence of a color factor in a heterozygous 
condition in one of the races experimented with. Perhaps Burtt- 
Davy's statements regarding the presence of a color factor for endo- 
sperm (i, pp. 172, 173, 177) resulted from an experiment of this type. 
I have not had access to papers with the data on which these state- 
ments are based. 
The preceding discussion assumes only one factor for yellow en- 
dosperm pigment, whereas East and Hayes, Collins and Burtt-Davy 
have each found at least two such factors. Further, Emerson and 
East (9, p. 11) suggest that orange endosperm color, such as is char- 
acteristic of Queen's Golden Pop, Tom Thumb Pop, Yardstick and 
some Chinese varieties (much intensified), is due possibly to the 
presence of a color intensifying factor. The F2 and F3 data on crosses 
of Z 14 X Z 21 show the presence of other color modifying factors, 
especially one which dilutes ordinary yellow to a very pale lemon 
color. Other investigators have also obtained this type. 
Summary 
I. Crosses of a yellow endosperm variety of maize (California 
Golden Pop) with a white endosperm variety (Z. Caragua) gave 
uniformly white progeny in Fi and a ratio approximating 3 W : I Y 
in F2. The F2 generation white grains, when planted, gave either all 
white F3 generation progeny or a mixture of white and yellow grains 
approximating a ratio of 3 W : i Y. The F2 yellow grains, except in 
two cases, produced all yellow F3 self-pollinated ears. The yellow 
grains in both the F2 and F3 generations varied considerably, and, in 
F3, ears wholly of very light lemon yellow grains were obtained. Un- 
protected ears of Z 21 in close proximity to varieties and hybrids 
having yellow endosperm always gave wholly white endosperm ears. 
