404 ORLAND E. WHITE 
yellows over that of Z 14 (California Pop) is to be inferred, as bagged 
ears are always of a uniform medium yellow. 
Unbagged ears of Z 2 1 {Zea Caragua) on plants grown under con- 
ditions similar to those mentioned for Z 14 have neyer been found in 
my cultures with yellow grains. Further, cultures of Z21 grown 
alongside of Fi and F2 generation hybrids (Z 14 X Z 21) have always 
produced (in my experience) only white ears. The Z21 cultures 
bloomed at about the same time as many of the hybrids, so that the 
difference in flowering time would not account for the absence of 
yellow grains. 
Interpretation 
In the light of the preceding data, endosperm color differences 
between Z 14 (California Pop) and Z 21 (Z. Caragua) may be regarded 
as due to the presence and absence of a single factor A. The presence 
of A prevents the development of the yellow color, when the factors 
for yellow pigment are present, and gives no indication of its presence 
in a variety from which these factors are absent. In the absence of A, 
a given variety may be either yellow or white. In respect to this 
factor A, then, and a single factor for yellow pigment, varieties of corn 
may be of four kinds: 
(1) AAYY (white endosperm) 
(2) AAyy (white " ) 
(3) aaYY (yellow " ) 
(4) aayy (white ) 
Crossed w^ith each other, these should give: 
Cross Fi F2 
i(W) X2(W) white (AAYy) all white 
i(W)X3(Y) white (AaYY) 3 W:i Y 
i(W)X4(W) white (AaYy) 13 W:3 Y 
2(W)X3(Y) white (AaYy) 13 W:3 Y 
2(W)X4(W) white (Aayy)! all white 
3(Y)X4(W) yellow (aaYy) 3 Y:i W 
So far as the data on Z 14 X Z 21 are concerned, California 
Golden Pop would be represented on the above scheme as aaYY, 
while the formula AAYY would be the only one applicable to Z21 
(Z. Caragua), All of the common white endosperm varieties of corn 
which are wholly or partially recessive to yellow endosperm color 
