R. P. Gregory 77 



whites, there appears the peculiar type knowu as " Duchess" (Plate XXXI, 

 figs. 27, 28), ill which the flower is white peripherally and has a coloured 

 centre. The mating of " Duchess " with plants having coloured flowers 

 and green stigmas, gives a tinged white F-^, exactly like that produced 

 by the mating of coloured, red stigma x dominant white. 



Various light shades of flower-colour behave as dominants to the 

 deep shades ; this dominance is due to the presence of factors which 

 efifect the partial suppression of the colour. These factors are quite 

 distinct, as regards their inheritance, from those described in the pre- 

 ceding paragraph. 



Similarly, the light shades of stem-colour are dominant to the deep 

 shades. The suppression of stem-colour is only partial, even in plants 

 homozygous for the suppressing factors, and no dominant green stems 

 are known. 



Flowers of a light shade may be borne by plants having deeply 

 coloured stems, but the deep flower-colours never occur on stems not 

 deeply coloured. It is clear, therefore, that the factor which effects 

 the partial suppression of stem-colour exerts its action also upon the 

 flower-colour. 



Besides the varieties constituted by combinations of the factors 

 already enumerated, there occur various types having flakes or patches 

 of colour (Plate XXXI, figs. 56 — 59)'. As in other oases where such 

 flaking has been encountered, the genetics of these varieties is not 

 altogether clear, but in the case of Primula sinensis, as will be seen 

 on reference to the text (p. 122), it is possible to frame a hypothesis 

 which would give results consistent with those observed. 



Gametic Coupling and Repulsion (p. 124). Complete repulsion 

 between the factor for the structural character of short-style and the 

 magenta colour-factor was observed in a series of experiments in which 

 short-styled salmon-pinks were mated with various long-styled plants 

 carrying the magenta factor. 



The cases of partial gametic coupling which have been met with 

 are interesting in that, in many of them, the two middle terms of the 

 F2 series are much larger, relatively to the end terms, than they are in 

 the majority of cases previously recorded. In the case of the coupling 

 between magenta colour and green stigma, the results of several 

 experiments approximate closely to the expectation based on the 

 hypothesis that a coupling of the form 7:1:1:7 is present in the 



' Flaked forms must be carefully distinguished from " Sirdars." 



