H. II. lilFKKN 227 



followiii',' season 500 piilliues, cuiit;iiiiiiig from 50 to 100 pl.irits each, 

 wore raised from individuals of the F., generation and since then a few 

 of the homozygous forms have been carried on to the F„ stage. No 

 counts of these later generations have been made but it is safe to say 

 that tlu' whole scries of plants contained at least 100,000 individuals. 

 Without exception the chaff colour was that of the Polish wheat. The 

 muiiiImt of plants dealt with appears to be sufficicmtly large to warrant 

 the sLatrment that in this casr the grey chaff character has been totally 

 suppressed. 



One or two other coloured forms have recently lieeii crossed with 

 Polish wheat in the hope of finding similar cases but without success. 

 V'arious red-chaffed wheats have given red i*', plants and a normal 

 segregation of three red to one white in the following generation whilst 

 a smooth black wheat (from Rivet x Red Fife) has given a blackish 

 Fi, segi-egating into blacks and white in the F^. It promises to be of 

 some interest however, for the colouring is confined to the plants with 

 short or intermediate glumes. Further crosses made with homozygous 

 forms of what may fairly be described as "alba" forms of Rivet wheat, 

 from the cross Rivet x Polish, have merely behaved as ordinary white 

 rough-chaffed wheats when crossed with smooth white varieties. 



The suppression of the grey character occurring in Rivet wheat 

 bears an obvious resemblance to the suppression of the type characters 

 when the rogues of culinary peas are crossed with the type plants. 

 There are however differences which may have some significance. The 

 F^ of rogue crossed by type or type by rogue shows clear signs of the 

 type in the early stages of growth, though these gradually disappear 

 and the plant becomes rogue-like and in future generations throws 

 rogues only. In the case of the wheat no signs of the grey character 

 can be detected at early stages of growth since this feature only develops 

 at the stage in which the grains of the plants are practically mature. 

 Further the colouring appears to be independent of any other features 

 which can be recognised in the early stages of gi-owth. In the peas 

 there is other evidence pointing to the fact that the type characters are 

 left behind in the base of the plant and consequently cut out of the 

 germ lineage'. But in wheat there is no great difference either in the 

 position or the date at which branches are formed. All of the branches 

 are basal, arising at ground level from nodes so closely clustered together 

 that they are almost unrecognisable. At first sight then similar 

 phenomena can hardly be looked for. Yet it is possible they exist for 



' Bateson and Pellew, Proc. Roij. Soc. Ser. B, Vol. lxxxix. p. 174. 



1.5—2 



