4 White Primula sinensis 



mately 13 white (and tinged) : 3 coloured. A departure from the 13 : 3 

 ratio should be noted in Experiment 2001. This must be attributed 

 to the fewness of the F^ plants grown, until more evidence can be 

 obtained. 



It was noticeable that some of the white plants of F^ from white 

 and coloured F^, showed a considerable increase of flaking as compared 

 with that observed in certain plants of Snow King. Among those 

 flaked, white plants from coloured F^ plants, there occurred one or two 

 plants bearing flowers with a very faintly tinged ground. 



Further investigations will, it is hoped, demonstrate the significance 

 of these facts. 



On the basis of the numbers obtained in F.,, we arrive at the 

 following conclusions:^ — The plant of Snow King used in Experiment 

 No. 200, which gives a tinged F^, is homozygous (TTTf) for the domi- 

 nant white factor. 



That used in Experiment No. 2 A, which gives a magenta J^i, is 

 homozygous {xvw) for the absence of the dominant white factor. Since 

 the flowers of this plant are white, it lacks a colour factor. That is, its 

 gametic constitution is cw. Since the stem is red, the loss of colour 

 factor has regard only to the flower and not the stem. 



Writing Snow King ciu and plant 2a, Cw, 



Fi = Ccw = coloured. 



The plant of Snow King used in Experiments Nos. 202 and .52 

 which give both coloured and tinged white in F^, is heterozygous (Ww) 

 for the dominant white factor. Since the variety as a whole breeds 

 true to whiteness, the heterozygous {Ww) plants must lack colour 

 factors. Their gametic constitution is cWw. 



Snow King (cWw) x Crimson King or Reading Pink (Cw). 



Fi = CcW'W, white or tinged white and Ccww, coloured. 



I I 



F,= 9CW,ScW,S Cw, 1 cw. F, = lCw,2 Ccw, 1 cw. 



= 9 white + 3 white + 3 coloured + 1 white 3 coloured : 1 white. 



= 13 white : 3 coloured. 



In order to investigate further the nature of the factors necessary 

 for the production of colour in Primula sinensis, plants of recessive 

 white Snow King were crossed with the recessive white, green stemmed 

 varieties of Ivy leaf (for a plant of which we are indebted to Mr Bate- 

 son) and Snow-drift. 



