226 The Siippression of CliaractcrH on Crossing 



nature between Rivet wheat and Red Fife a diiferent state of affairs is 

 met with. The F. generation in this case contained black, grey and 

 white-chaffed wheats. Several F.^a of this jjarentage have been raised, 

 giving in all some 2000 plants, but the number is inadequate for a 

 comjjlete statistical examination, in view of the fact that a large 

 percentage of the plants are sterile and consequently one cannot obtain 

 much information from the F^ generations. The most that can be said 

 at present is that there are two classes of blacks, one rough and one 

 smooth, corresponding forms amongst the white-chaffed individuals and 

 no smooth greys. 



Crossing the smooth black with rough white, the nearest approach 

 so far possible to introducing one of the dominant characters on either 

 side of the parentage, results in an F. generation showing coupling on 

 a 3 : 1 : 1 : 3 basis'. 



Crossing Rivet wheat with Polish wheat (Triticum polonicum) gives 

 a totally different result to any of the crosses with T. vulgare. This 

 wheat has white glumes which are so slightly hairy that they are 

 generally described as glabrous. The glumes are further characterised 

 by their enormous length which under ordinary conditions is some three 

 times as great as that of any other wheat. The F^ plants of this 

 parentage, no matter which way the cross is made, have a pale grey 

 chaff. Isabelline white is probably the most accurate description that 

 can be given of the colour. It is not unlike that of the Polish wheat, 

 but a faint grey tinge is present much as there is a tinge of blue in 

 many white-flowered varieties of Campanulas derived from blue species. 

 Thus the full dominance of grey seen in all of the other Rivet crosses 

 is wanting. 



The F^ generations from these crosses differ altogether in their 

 general character from the crosses with the varieties of T. vulgare. 

 The latter are characterised by the occurrence of a bewildering, though 

 evidently definite, series of unexpected forms such for instance as plants 

 with bright grass green instead of glaucous foliage, with ears of the 

 spelta type, with branching cars, dwarfs, etc. The former show no such 

 features but merely individuals with the short or long glumes of the 

 parents and a series of plants with an intermediate glume length. The 

 short and the intermediate glumes are all markedly rough whilst the 

 long-glumed forms are practically glabrous. Throughout the whole 

 series containing over 2000 plants raised from 20 separate F^'s the 

 glume colour was identical with that of the Polish wheat. In the 



' Engledow, Proc. Camb. Phil. Soc. 



