W. O. Backhouse 127 



class, the roughs predominate in the ordinary ^ : 1 proportion (Chart, 

 Fig. 1 b). 



Felted Glume Smooth 



40 15 



Expectation ... 41-fi5 13-75 



Examining 56 individuals, the theoretical expectation of homozygous 

 longs, and beginning at the extreme long end of the curve, it was found 

 that there were, among them, no individuals which could be called felted, 

 though with a lens a short velvety pubescence was seen on most. Among 

 the individuals with glume length between 15 mm. and 22 mm., which 

 may roughly be said to comprise the heterozygotes, the proportion was 

 85 felted to 31 smooth ; but here there were only 15 individuals which 

 could confidently be called felted — in the majority of cases the closest 

 scrutiny was needed to determine to which category they belonged. 



Finally the long class were examined critically — with the help of a 

 lens and the individuals selected which apjjeared to be absolutely smooth 

 — as smooth as the original short glumed Kubanka. These plants were 

 grown the succeeding year and found to be all pure longs except two, 

 and, what is more imjjortant, a careful inspection with a lens showed 

 them to be also breeding true to this smoothness; a smoothness which, 

 however, turned out to be only apparent in some cases. 



Test crosses were made between these smooth lines and the original 

 Kubanka, also other durums, to see whether the presence of the pubes- 

 cence in any way affected the segregation of glume length. The second 

 generations fi-om these test crosses were surprising for, while some were 

 all smooth, others behaved in the same way as the original cross (giving 

 a 3 to 1 proportion of roughs and smooths among the short glumed 

 class), differing only in that the pubescence was of a minor degi-ee, as 

 exemplified in the Canadian variety Prelude. From this it will be seen 

 that the long glume was able to inhibit the expression of a dominant 

 character' and, furthermore, that there was a direct relation between 

 the length of the glume and the degree of felting — the greater the 

 glume length, the less being the pubescence, even among the variable 

 heterozygotes. This will be better illustrated in the following case. 



The same variety of T. polonicum used in the first experiment was 

 crossed with a felted, black glumed variety of T. turgidum, not unlike 

 Eivet wheat of which it is, in fact, a descendant. The average glume 

 length of the turgidum is 11 mm. and of the polonicum 28 or 29 mm. 

 The first generation was intermediate in glume length — varying between 

 14 mm. and 17 mm. It was fairly felted and in colour white or faintly 



