126 Glume-Length and GrainrLength in Wheat 



acted as an inhibitor of pubescence." Confirmatory evidence cannot be 

 sought from the ^3 plants, for it is found that, comparatively quickly, 

 glume hairs fall off or become so brittle that they are very readily 

 rubbed off in handling, and the F^ plants have been stored for five 

 years. 



IX. The Inheritance of Solidness of Straw in the Cross. 



When the " shift " in glume-length became apparent, it was decided 

 to investigate some character unconnected with glume- or grain-length, 

 to see if it manifested in F2 any feature corresponding to the shift of 

 glume-length. The straw was selected. P is solid, K is hollow, and it is 

 noteworthy that in all cases in which " shift " of glume-length is observ- 

 able [vide cases cited in § IV above], one parent was solid in straw and 

 the other hollow. Absence of shift characterises one case only, viz. the 

 Polish X Rivet cross [Biffen (1)], and in this both the parents are solid 

 in straw. Thus the nature of the straw might possibly be related to the 

 shift in glume-length. 



Biffen (1) for a Turgidum (solid) x Vulgare (hollow) cross (Rivet 

 and Red King were the varieties actually used) found a sharp 3:1 = 

 hollow : solid in ^2- In the cross here described it was difficult on many 

 occasions to separate hollow and solid straws. " Intermediate-solids " 

 were encountered and finally were included as solids. The t\ was 

 classified for straw by examination of its F^ progenies, but in all three 

 of the glume types (P, /, and K) the ratios were such as could not be 

 ascribed to ordinary factor segregation, whether of one or more than one 

 factor. Different ratios were found for every one of the glume-type 

 constituents {K, I, and P) and a different one, again, for the complete F^. 



The result is therefore negative — shift of glume-length is not con- 

 nected with any simple peculiarity of straw inheritance — but the fact 

 that unaccountably irregular ratios were obtained points to the need of 

 a continuation of the straw investigation in subsequent generations. 



X. Evidence concerning the Endosperm in Inheritance. 



That grain-length is a maternal character was one of the conclusions 

 arrived at by a comparative study of the inheritances of glume-length 

 and grain-length [see § VI (7), p. 123 above]. Singleness of length-type 

 of all grains borne by "/" plants was manifestly a sine qua non of the 

 acceptance of such a conclusion and it was thought well to re-examine 

 the "/" grain question both theoretically and in practice. 



