VIII WILD AND DOMESTIC VARIETIES 75 



dominant to the dark winged form ; and (2) a factor 

 for intense colour, which occurs in the bicolor and in 

 the deep purple, but is lacking in the dilute picotee. 

 And here it should be mentioned that these con- 

 clusions rest upon an exhaustive set of experiments 

 involving the breeding of many thousands of plants. 

 In this cross, therefore, we are concerned with the 

 presence or absence of five factors, which we may 

 denote as follows : — 



A colour base, Ji. 



A colour developer, C. 



A purple factor, £. 



A light wing factor, Z 



A factor for intense colour, 7. 



On this notation our six coloured forms are : — 



(i) Purple bicolor . CRBLI> 



(2) Deep purple CRBII. 



(3) Picotee .... CRBLi or CRBli. 



(4) Red bicolor ( = Painted Lady) CRbLI. 



(5) Deep red ( = Miss Hunt) . CRbll. 



(6) Tinged white . . . CRbLi or CRMi. 



It will be noticed in this series that the various 

 coloured forms can be expressed by the omission of 

 one or more factors from the purple bicolor of the 

 wild type. With the complete omission of each 

 factor a new colour type results, and it is difficult 

 to resist the inference that the various cultivated 

 forms of the sweet -pea have arisen from the wild 

 by some process of this kind. Such a view tallies 

 with what we know of the behaviour of the wild 



1 It is to be understood that wherever a given factor is present the 

 plant may be homozygous or heterozygous for it without alteration in 

 its colour. 



