MODERN PLANT-BREEDING METHODS 721 



these characters have so far failed, and at present it appears 

 to be impossible to breed a smooth, grey chaffed wheat. In 

 the case of a cross between the rough grey Rivet wheat and 

 the smooth white Polish wheat, however, rough chaffed white 

 wheats have resulted. The cross was made in both directions, 

 giving in each case a hybrid with rough chaff which was 

 slightly tinged with grey. Several thousand plants were raised 

 from the hybrids, but not one of these showed the dark grey 

 colour of the parent Rivet. The plots appeared to contain 

 white chaffed wheats only. An examination, individual by 

 individual, showed that here and there the merest traces of grey 

 could be detected in some few cases, and one plant was found 

 with awns of a brownish colour approaching that of Rivet 

 wheat. The individuals with the most pronounced colouring 

 were selected for raising a further generation from, but they 

 again produced white chaffed wheats, with either no traces of 

 colour or the merest tinge. The grey colouring then appears 

 to have disappeared. This is probably the nearest approach 

 to the phenomenon of monolepsis or false hybridism which has 

 been seen since Millardet's much-discussed experiments with 

 strawberry hybrids. In pre-Mendelian times a fair summary of 

 the result would be to say that the hybrids bred true directly to 

 the white colour. It is probable that further crosses will throw 

 some light on this suppression of the grey colouring. 



A statistical examination of the crop showed that there 

 were three rough chaffed individuals to one smooth chaffed — 

 the result expected if smoothness is recessive. The smoothness 

 of the chaff was, however, confined to those individuals which 

 were characterised by the possession of long glumes like those 

 of the Polish wheat. Consequently all the plants with short 

 glumes similar to those of Rivet wheat, and the heterozygotes 

 with glumes of an intermediate length, had rough chaff. In this 

 case, then, there is a coupling of the rough chaff character with 

 the glume length which will entail further investigation. 



From the account of the experiments given above, it is clear 

 that Mendel's laws of inheritance are of wide application, and 

 their value to those who would attempt to improve our culti- 

 vated plants is obvious. The breeder now has to recognise 

 the fact that his plants are built up of a series of units for the 

 most part capable of separate segregation when crosses are 

 made. As a direct consequence of this, fresh combinations of 



