K. P. Gregory 123 



colour in the flaked condition. A re-examination of the parent " Ivy- 

 leaf" in the light of this suggestion failed to reveal any definite 

 coloration, but the pale colour is at best sometimes hard to discern 

 and in the flaked condition might escape even close inspection, 

 especially in such poorly developed flowers as are characteristic of the 

 " Ivy-leaf." The suggestion is moreover supported by the fact that 

 Keeble and Pellew^ obtained a flaked Fi from the cross of an "Ivy-leaf " 

 of this strain with "Snow King." This view of the constitution of 

 the " Ivy-leaf" would agree well enough with the results of the cross 

 with " Snowdrift," for the latter possesses the factor for self, as 

 against flaked, colour, and we should therefore expect a ratio of 

 9 self-coloured : 7 flaked and white. 



In the same way the absence of pale-pinks in the F^ of the cross 

 with " Primrose Queen " may perhaps be put down to the difficulty of 

 recognizing the colour in its most dilute and flaked condition-. The 

 complete absence of self-colours from this ^3 is interesting in view of 

 the results of the cross between " Primrose Queen " and " Snowdrift," 

 and suggests some considerations as to the relation between flakes and 

 self-colours. For if the self-colours result from the addition of a 

 " distributing " factor epistatic to the factors for colour, it is clear that 

 "Primrose Queen" must be without this factor; but in that case 

 one-third of the coloured ofi^spring obtained in the F., from (" Primrose 

 Queen " x " Snowdrift ") sh<mld be flaked, and no flakes have been 

 obtained in this cross. 



If, then, the conception of distributing factors is to be retained, it 

 would be necessary to construct an elaborate scheme of factors, for the 

 existence of which there is at present no evidence. In the absence of 

 such evidence, it is more simple to suppose that one, at least, of colour 

 factors may exist either in the flaked or in the distributed condition. 

 The ^1 from (self-colour x flake) then appears self-coloured because the 

 flaked character is masked when the flower as a whole is coloured'; 

 and the segregation which takes place in the hybrid consists in the 



* Joum. Genetics, Vol. 1. 1910, p. 4. 



* Flaked pale-pinks have now (Feb. 1911) been definitely recognized in F, from this 

 cross. A red-stemmed magenta flake, self-fertilized, gave two kinds of ofifspring, namely 

 (1) plants with red stems and flowers flaked magenta, (2) plants almost devoid of colour 

 in the stem, in the flowers of which the flakes of pale pink were rec(^:nized with certainty. 

 Temperature of the house, 5-5° F. 



* Whether any pale self-colours, crossed with flakes, would give an Fj of a visibly 

 flaked character depends upon the relation between full and pale colours, which is not yet 

 fully understood. 



9—2 



