Mr Engledow, A Case of Repulsion in Wheat. 435 
That still other factors must be assumed to be concerned in 
this colour effect is clear from an examination of the parentage 
of “Smooth Black.” The black appeared in the second generation 
of a cross in which neither of the parents showed the black colour. 
This, of course, would lead us to assume that in each parent is a 
factor which alone cannot produce blackness but united with the 
other has this effect. No simple explanation can, however, be 
furnished on these lines and it seems probable that before the 
question can be settled more knowledge will have to be obtained 
of the nature of true “black” and “grey.” ‘Transverse sections of 
the glumes may be of some assistance in this respect. Meantime, 
the repulsion above described seems certain and from the nature 
of the case there appears to be a strong probability that Rivet 
“orey ” and true “black” are very closely related. It is hoped to 
elucidate this matter by further crosses next summer. 
A double confirmation of the existence of repulsion between 
blackness and roughness seems possible. The doubly heterozygous 
members of the second generation ought to exhibit repulsion ; 
and coupling between the two characters should result from the 
erossing of “Rough Black” and “Smooth White.” These two 
types can, of course, be obtained from the second generation which 
exhibited the repulsion. 
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