HYBRIDISATION AND WHEAT HYBRIDS 393 



leaves, red glumes, white grain, solid straw, and the early habit of the 

 male grandparent. 



On account of the irregular development of the glume pigment in 

 the homozygotes and the intergrading of glume colour among the hetero- 

 zygotes, accurate classification by eye-inspection alone was impossible. 



The F 3 generation showed, however, that the F t generation consisted 

 of the following segregates : 



T. dicoccum forms : 



(1) Homozygous black glumes or blackish glumes with darker margins. 



(2) Homozygous uniform white glumes. 



(3) Heterozygous white glumes with black margins, splitting into i 



white : 3 grey or blackish glumes. 



(4) Heterozygous uniform red glumes, splitting into i white : 3 red. 



(5) Heterozygous red glumes with black margins, splitting into i white : 



3 white with black margins : i red : 3 red with black margins. 

 T. durum form : 



(6) Uniform red glumes. 



Factors for black, red, and white glumes were present in the F,, those 

 for black and red being apparently brought in by the black-glumed 

 Emmer parent, the allelomorphic pairs of the cross being black and red, 

 and black and white respectively. 



The original parental dwarf spharrocofcum type of ear and straw 

 disappeared altogether in this cross, and was not recovered as a recessive 

 in the F 2 or F s generations of the hybrid, its place apparently being taken 

 by the durum form : the white colour of its grain was seen, however, in 

 the durum, and the peculiar curved apex of its empty glumes was visible 

 among the majority of the segregates of F. and F 3 . 



The factor for beardlessness was not dominant in F, of this cross, 

 and its influence was only slightly seen in the F, and F s among a few of 

 the heterozygous plants (No. 3 above) which had shorter awns than t he- 

 normal difoccum. 



In all these forms pubescence was linked with the black character. 



(e) The hybrid 7\ tt*/<*rr, var. lutescens (Fultz Mediterranean) 

 T. dicoccum, var. atratum (Black Fmmer), obtained by Ke/er and Boyack, 

 had the flattened ears and the dark, adherent, keeled chaff of the Emmer 

 parent. The ears were " beard-tipped " and non-glaucous, the latter 

 character being found in the rulgare parent. 



The F 2 generation was extraordinarily diverse, from sixty-two to sixty- 

 five distinct forms appearing, among which were examples of T. tlicuccum, 

 T. ru/gare, and T. Sftt'lta. In outline, density, and other characters the 

 ears were equally diverse, many being quite unlike either grandparent. 



Numerous grades were found between long and short, and lax and 

 compact. 



