WAXY ENDOSPERM IN HYBRIDS WITH SWEET CORN. 23 
versely, that what is lacking in the waxy 1s supplied by a sweet 
variety. While the horny seeds resulting from the cross between 
sweet and waxy were indistinguishable from ordinary horny seeds, 
it was, of course, to be expected that differences would appear in the 
progeny. 
Four of the six ears obtained as a result of the crosses made in 
1911 were selected for planting in 1912. The ancestry of these ears 
is as follows: 
Dh221. White Chinese (waxy) X Voorhees Red (sweet). 
Dh209. White Chinese (waxy) X Black Mexican (sweet). 
Dh216. White Chinese (waxy) X Black Mexican (sweet). 
Dh207. White Chinese (waxy) X Black Mexican (sweet). 
The same individual plant was not used as the parent of more than 
one cross. 
From these 4 ears 55 ears were produced in 1912. Every ear bore 
seeds of all three classes—horny, sweet, and waxy. The entire 55 ears 
had 22,132 seeds, of which 57.4 per cent were horny, 24.8 per cent 
sweet, and 17.8 per cent waxy. These proportions approximate the 
9:4:3 Mendelian ratio involving two factors. 
Since in the first generation sweet combined with waxy produced 
horny, it has been assumed that something necessary to produce 
horny is lacking in both the sweet and the waxy, and an attempt has 
been made to analyze the behavior of these hybrids with this idea in 
view. The residual factor which when it occurs alone is assumed to 
cause the sweet character will be called S, while Y will be used to 
indicate the factor of the waxy character. Small letters, s and a, are 
used to denote the absence of these factors. Since in both sweet and 
waxy the alternative factor necessary to produce horny is assumed 
to be lacking, the gametes produced by sweet varieties will be repre- 
sented by Sa and the gametes produced by varieties with waxy 
endosperm by sX. The synthetic horny will then be represented by 
a combination of these, or SvsY. Assuming a chance recombination 
of these factors in the gametes derived from these synthetic horny 
seeds, the gametes will be of four kinds. Both the sweet and the 
waxy may be present (S.1’), or the sweet may be present without 
the waxy (Sw), or the waxy without the sweet (s1’), or both may be 
absent (sa). At fertilization each of these kinds of gametes may 
unite with any one of the four corresponding kinds derived from the 
other parent, producing 16 zygotic combinations. The formation of 
these combinations is represented in the conventional diagram, 
figure 1. The four classes of gametes from one parent are given in 
the horizontal row at the top, and the same four classes from the 
other parent in the vertical row at the left. Each gametie combina- 
tion from the top is repeated four times in the squares below, while 
[Cir. 120] 
a ere 
ee 
eS SR RS SS 
er +a oe ae Pee es = 
abet Se 
eae 
ne 
ee 
= ae ai 
— =a 
; - mot . 
ee 
