R. P. Gregory 111 



does, in reality, depend upon the combination of two factors (of which 

 "Snowdrift" must be assumed to have both) the rosy-magenta used 

 in the 1909 experiments may have been heterozygous for one of them, 

 without giving us any clue other than that which is suggested by these 

 experiments. The mating between a sister plant of the rosy-magenta 

 used in experiment No. 17/10 and a dominant white gave magentas 

 and rosy-magentas in F.^. The separation between the two classes was 

 somewhat doubtful, but they apparently consisted of 20 and 19 plants 

 respectively. So far as this observation carries weight, it tends to 

 support the view that the difference between the two classes depends 

 on the combination of two factors. 



" Crimson King." In all its crosses " Crimson King " gives a great 

 variety of coloured forms in F^, and it is clear, both from the number 

 of these forms, and from the comparative rarity with which the 

 " Crimson King " type itself reappears, that its visible characters 

 result from the interaction of several factors which are partially or 

 wholly independent of one another in segregation. 



A series of F., forms from the cross with the dominant white 

 " Queen Alexandra " is shown in Plate XXXI, figs. 22 — 43. The types 

 possessing some form of inhibition will be dealt with under that head 

 (p. 11.5). Among the coloured forms (figs. 33 — 43) various types of light 

 and dark magentas and reds occur, with or without the coloured stigma. 

 This last character is recessive to the factor inhibiting the development 

 of colour in stigma, and the observed numbers of green (colourless) 

 stigmas and red stigmas approximate very closely to the ratio 3 : 1. 

 But in the great majority of my experiments the two kinds of stigma 

 are not evenly distributed among the magentas and reds, and there is 

 clear indication of the existence of partial gametic coupling between 

 the two factors magenta and green stigma (p. 127). "Crimson King" 

 has the factor determining the spot of dark colour on the petals and 

 accordingly this character appears in deeply-coloured flowers which 

 have the coloured stigma and the ordinary or large yellow eye. 



" Crimson King " x " Snowdrift." The Fj from this cross is an 

 ordinary (light) magenta. The F„ contains fully coloured forms corre- 

 sponding with those just described \ and in addition to these there 

 occur magenta and red " Sirdars " (figs. 44, 45) in light and deep 

 forms, pale-pinks (fig. 46) and whites, the last two classes having green 



' The white eye is a character derived from "Queen Alexandra" and does not appear 

 in the experiments with " Snowdrift." 



