164 Inheritance in the Stock (Matthiola incana) 



represent the factorial relations now shown to be involved in these two 

 unions as set out below : 



Half-hoary x Coloured sub-glabrous 



Parents 



^1 



Fully hoary type x 

 {incana) 

 CRHK 

 CRHK 



Half-hoary 

 variety 



(semi-incana) 

 CRHiK 

 GRHiK 



All fully hoary 

 CRHK 

 CRHiK 



variety 



(semi-incana) 



CRHiK 



CRHiK 



form containing K 

 CRK 

 GRK 



All quarter-hoary 

 CRHiK 

 CRK 



3 Fully hoary : 1 Half-hoary 

 in the proportion of 

 1 CRHK : 2 CRHK CRH^K 



CRHK CRHiK CRH^K 



1 Half-hoary : 2 Quarter-hoary : 1 Sub-glabrous 



CRHiK 

 CRHiK 



CRHiK 

 CRK 



CRK 

 CRK 



The allelomorphic nature of the factor Hi having thus been demon- 

 strated from qualitative results in the cases given above it remains to 

 show in detail that the quantitative composition of the F2 generation 

 from various unions is closely in accord with expectation based on this 

 relation. Revising our earlier prediction' (calculated on a scheme of 

 distinct as opposed to allelomorphic factors) we shall now restate and 

 amplify this expectation (see p, 165). 



In order to obtain proof of the correctness of the expectation there 

 given for the various possible combinations of C, R, H, and K with H^ 

 it was necessary in the first place to produce individuals which should 

 contain ^1 without either H or K. To this end a glabrous F.^ plant 

 from the mating GRH x GRK (forms obtainable commercially) found 

 to lack both H and K was bred with semi-incana. The resulting cross- 

 bred was then bred back with the glabrous strain GRH, from which 

 mating mixed families were obtained containing about equal numbers 

 of fully hoary and glabrous individuals. As the gametic unions 

 GRH^K X GRH and GRK x GRH would give fully hoary it followed 

 that the approximately equal number of glabrous plants must consist 



GTiTT GT} 



of the two classes nT>T^ and nT>TT- A further back cross between these 



smooth plants and semi-incana yielded again mixed families, some con- 

 sisting of fully hoary and partially hoary, others of fully hoary and 

 glabrous individuals. Clearly these partially hoary plants which were 

 of a new type must result from the gametic union GRH^ x CRH^K. 

 In this way the mid-hoary form was first synthesised and identified, and 

 a pure GRH^ strain eventually raised. The graphic representation shown 

 ^ Journal of Genetics, loc. cit. p. 157. 



