R P. Gregory 105 



part ; the I'esults are such as to indicate that the flaked condition 

 behaves as a recessive to the self-colour (see, however, p. 122). 



The pale-coloured flowers on green stems are scarcely affected in 

 appearance by the presence or absence of the numerous factors which 

 produce such marked changes in the fully coloured types of flower. 

 It is often by no means easy to recognize the pale colour when it occurs 

 in the flaked condition ; this is no doubt an optical difficulty, for the 

 lower forms of this colour in any case need careful examination in 

 order to distinguish them from white. Among the pale-pinks there 

 occur forms in which the colour is more pronounced peripherally, others 

 in which it is central, others again in which it forms peculiar bands. 

 But the diflScuIty of observation is such that no attempt has yet been 

 made to study the inheritance of these variations. 



Partial Suppression of Colour. 



As in the case of stem-colours, the intense colours of the flowers are 

 produced only in the absence of a factor which diminishes the intensity 

 of the pigmentation, and so gives rise to the dominant light shades. 

 The partial suppression of flower-colour may be brought about by 

 either of two factor.?, of which one affects the flower only, the other 

 the whole plant. Hence light flowers may occur in association with 

 dark stems, but deeply coloured flowers are limited to plants with 

 deeply coloured stems. 



In many F2S there occur classes intermediate between the lightest 

 and the very deep types, but, though the existence of such classes may 

 be clear enough, it is difficult, if not impossible, to draw any sharp line 

 between them, and, as in the case of stem-colours, it must remain 

 undecided whether one pallifying factor, in its various pure and 

 heterozygous combinations, is sufficient to account for all the shades, 

 or whether a series of such factors is involved. 



The factors which effect the partial suppression of colour seem to 

 differ in degree rather than in kind from the factors which, in pure 

 races, completely inhibit the development of colour in the flower. 



Inhibition. 



In the red-stemmed " Dominant Whites'," the whiteness of the 

 flower is due to the presence of a substance which inhibits the 



' Gregory, Rep. Brit. Assoc, Leicester, 1907, p. 692. 

 Journ. of Gen. i 8 



