VoLUMK V JULY, rjlG No. 4 



THE 8UPP11ESS1()N OF CPrAllACTERS 

 ON CllOSSING. 



By R. H. BIFFEN, F.R.S., M^ 



School oj Affriculture, Cambridge. ^ '''C^^ 



The publicatioTi in a previous issue of this Journal of the papei' 

 "On the genetics of 'rogues' among culinary peas'," in whicii attention 

 is called for the first tinn' to a case in which a group of characters 

 introduced by one of the original parents fails to affect the F., generation 

 has led me to place a somewhat similar case on record in spite of the 

 fact that the investigations dealing with it are still far from complete. 



The character in this instance is the mouse-grey colour occurring in 

 the glumes of the well-known Rivet wheat (Triticum turgidum). In this 

 variety, and indeed in all of the grey-chaffed wheats I have been able 

 to obtain up to the present, gi'eynoss is invariably associated with the 

 presence of a quantity of silky hairs on the glumes so that all grey 

 wheats are "rough-chaffed." The converse that all rough-ehaffed wheats 

 are grey however is not true, for white and red rough-chaffed varieties 

 are moderately common. 



Crosses between red or white rough-chaffed wheats and varieties 

 with glabrous chaff show simple dominance of roughness followed by 

 segregation into rough and smooth in the j^rojjortions of three of the 

 former to one of the latter. 



Where however roughness is associated with greyness, as for instance 

 where Rivet wheat is used as a parent, the two chai-acters tend to be 

 coupled. In certain crosses with varieties of Triticum vulgare the 

 coupling appears to be complete since all of the rough-chaffed forms 

 occurring in the F2 generation have gi'ey chaff In such cases the ratio 

 for rough grey to smooth white is as 3 : 1. However none of the 

 Fn generations have so far exceeded some 300 individuals so that there 

 is the possibility that the expected smooth grey and rough white might 

 occur if still lai-ger numbers were raised. In another cross of the same 



' W. Bateson aud Caroline Pellew, Journ. of Genetics, Vol. v. p. 13. 

 Jouiii. of Gen. v 15 





