108 Experiments with Primula sinensis 



Experimental results. (1) Pale colours. 



Pale-pink (Plate XXX, fig. 13 ; Plate XXXI, fig. 46). Pale-pinks 

 have occurred in the F^s of all ray crosses between full colours and 

 " Snowdrift," as well as among the progeny of certain heterozygous 

 full colours obtained from various sources. It is also the characteristic 

 coloured form thrown by heterozygous dominant whites having green 

 or only slightly coloured stems. If the pale-pink be crossed with 

 " Snowdrift " the resulting F^ shows some dilution of the colour. 



Heterozygous pale-pinks can throw nothing but pale-pinks and 

 whites, and this they do in the proportion of 3 pinks : 1 white, the 

 numbers obtained being 51 pink, 16 white. One of these plants 

 crossed with "Snowdrift" gave 23 pink, 17 white. 



My experiments throw no definite light on the question of the 

 dependence of the colour on two complementary factors, a chromogen 

 and a ferment, but in this connexion the cross between "Ivy-leaf" and 

 " Snowdrift " should be mentioned. Both parents appear white, while 

 the hybrid has definite though faint colour in the flowers. In F.2 

 plants with definitely coloured flowers form approximately 9 in every 

 16 plants, the observed number being 144 coloured in a total of 273 

 plants. Subsequent experiments with the " Ivy-leaf," however, suggest 

 the possibility that, instead of its being a white, as I had supposed, it 

 may have the very pale pink colour in the flaked condition (see p. 122). 



The pale-pinks may or may not carry the magenta factor. Of 

 10 pale-pinks tested by crossing with reds, 6 were pure for the magenta 

 factor and gave 65 offspring, all magenta ; 2 were heterozygous and 

 gave 30 offspring, 14 magenta, 16 red ; and 2 were without the magenta 

 factor and gave 16 offspring, all red. One other, mated with a magenta 

 throwing magentas and reds, gave 5 magenta, 5 red, and was therefore 

 without the magenta factor. 



The same set of experiments served to reveal other characters 

 carried by the pale-pink. Nine F^ pale-pinks from the cross (" Crimson 

 King" X "Snowdrift") gave offspring when crossed with "Orange 

 King." In the resulting families there occurred intense and light 

 colours, in one case rosy-magentas as well as the usual kind, in another 

 case deep crimson-magentas together with reds very like "Crimson 

 King," while in some cases the spot of deep colour was present in all 

 the offspring having coloured stigmas, in others in only a proportion of 

 them^ One pale-pink without colour in the stem was found to have 



1 See Table, p. 107. 



