Nov. 12. 1921 Genetic Behavior of Spelt Form in Crosses 343 



In series 13126a (Table IV), only 4 wheats were produced in a popula- 

 tion of 74 F2 plants, while in series 3019a, 2 wheats were produced in an 

 F2 population of 83 individuals. The deviation from the 3 to i ratio is 

 so great that even by grouping class 9 with class 10 — that is, by making 

 generous allowances for observational error — the proportion approached 

 more nearly the 15 to i ratio. On the basis of the 15 to i ratio, the 

 expectation in series 13126a, is 69.4 to 4.6, in series 3019a, 77.8 to 5.2. 

 The deviations are 0.6 and 3.2, and the probable errors ±1.40 and 

 ± 1.49, respectively. 



On examining the Fg generation produced from 27 plants of series 

 13126a, it was found that 12 of these had produced only spelts (Table V), 

 two plants yielded only sativum types, and the remaining 13 F2 plants 

 yielded progeny of mixed forms. Assuming that the spelt parent in 

 this particular cross carried two spelt factors, Sj and Sj,^ the first two 

 generations will consist of the following genotypic forms: 



If these genotypes were carried through the F3 generation the theo. 

 retical behavior of each of the Fg plants would be as follows: 



GROUPS. F2 GENOTYPES. PHENOTYPES OF THE Fs AND THEIR BEHAVIOR IN THE F3 GENERATION. 



A I SjSjSjSj I wheat will yield wheat only. 



B I SjSiS2S2 



2 t3iOi02S2 



1 S1S1S2S2 



2 DiSib202 

 I SiSjv!)2v32 



C 4 SiSiS2S2 4 Spelts will segregate 15:1 



15 2 S1S1S2S2 1 ^ cr.«ife will oo^.-o„o+» ... \^ unstable forms. 



>7 spelts will yield spelts only. 



4 SiSiS2S2 4 spelts will segregate 15:1 | 



2SisaS }4 spelts will segregate 3:1 f 



Total 16 



When the performances of the Fj plants were examined, a close 

 approximation was found to the above-mentioned theoretical ratios. 

 The numbers of constant wheats, constant spelts, and unstable spelt 

 forms obtained are shown in Table V, together with the theoretical 

 expectations. 



' In the factorial explanations given in this paper the spelt factors are assumed to be Si and S2. Although 

 the assumption of the factors si and sz to stand for the wheat (T. sativum) character will fully agree with the 

 results obtained, so far as the ratios go, there is no evidence as yet to warrant the assumption that the wheat 

 and spelt characters are allelomorphic to each other. In fact, results with other specific crosses show the 

 possibility that these are caused by two sets of independent factors. The behavior of the sativum X spelta 

 crosses may be compared with the behavior of a maize cross where one parent has yellow endosperm and 

 purple aleurone color (YYCCPP), and the other differs from this by its lack of purple color (YYCCpp). 

 In such a cross, where the F2 shows segregation into 3 purple to i yellow, the assumption that yellow and 

 purple are allelomorphic may be used as a working hypothesis for crosses of this type, although it is not the 

 correct explanation, as endosperm and aleurone color are two different characters altogether. 



