WAXY ENDOSPERM IN HYBRIDS WITH SWEET CORN. 23 



verseh', that what is Licking in the waxy is supplied by a sweet 

 variety. ^Vllile the horny seeds resulting from the cross betw^een 

 sweet and Avaxy were indistinguishable from ordinary horny seeds, 

 it Avas, of course, to be expected that dilferences 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: 



Dh22]. White Cblnese (waxy) XYoorhees Red (sweet). 



Dh209. White Chinese (waxy)X Bl:ick Mexican (sweet). 



Dh21G. 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 w^axy. The entire 55 ears 

 had 22,132 seeds, of wdiich 57.4 per cent were horny, 24.8 per cent 

 sw^eet, 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 wath waxy produced 

 horny, it has been assumed that something necessary to produce 

 horny is lacking in both the sAveet and the waxy, and an attempt has 

 been made to analyze the behavior of these hybrids Avith this idea in 

 vieAV. The residual factor Avhich Avhen it occurs alone is assumed to 

 cause the sweet character Avill be called S, Avhile X Avill be used to 

 indicate the factor of the Avaxy character. Small letters, s and £», are 

 used to denote the absence of these factors. Since in both SAveet and 

 Avaxy the alternative factor necessary to produce horny is assumed 

 to be lacking, the gametes produced by sweet varieties will be repre- 

 sented by /Sx and the gametes produced by varieties Avith Avaxy 

 endosperm by sX. The synthetic horny Avill then be represented by 

 a combination of these, or ^SxsX. Assuming a chance recombination 

 of these factors in the gametes deriA'ed from these synthetic horny 

 seeds, the gametes will be of four kinds. Both the SAveet and the 

 waxy may be present (SX), or the sweet may be present Avithout 

 the Avaxy (aS'j'), or the waxy without the sAveet (sX), or both may be 

 absent (sx). At fertilization each of these kinds of gametes may 

 unite Avith any one of the four corresponding kinds derived from the 

 other parent, producing 10 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 roAv at the top, and the same four classes from the 

 other parent in the vertical row at the left. Each gametic combina- 

 tion from the top is repeated four times in the squares beloAV, while 



[Cir. 1201 



