110 Cliemistnj of MendeUan Factors for Flower-Colour 



Of these factors : 



Y represents the power to produce a very pale yellow (ivory) pigment 

 in the tube of the corolla and a deep j'ellow pigment in the lips of 

 the corolla with a still deeper yellow patch' on the palate (PI. V^II, 

 fig. 2). The composition of a plant bearing yellow Howers may be 

 represented as: 



YY{y)nrrB(b)B(b) yellow. 



/ represents the power to form ivory pigment in the tube and lips, and 

 to inhibit the formation of yellow pigment in the lips except on the 

 palate. The composition of a plant bearing ivory flowers (PI. VII, 

 fig. 3) is: 



YY(ij)II{i)rrB(h)B{h) ivory. 



R represents the power to produce red anthocyanin pigment in the 

 corolla'^. If the ivory factor is absent, the red is mixed with yellow 

 and the result is bronze (PL VII, fig. 4) : 



YY{y)iiRR{r)bh bronze. 



If the ivory factor is present, the result is rose dore (PI. VII, fig. 5): 



YY{y)II{{)RR{r)hh rose dor^. 



B represents the power to convert the red anthocyanin into bluish-red 

 or magenta anthocyanin. If the / fiictor is absent, the result is a 

 mixture of magenta and yellow, i.e. crimson (PL VII, fig. C) : 



YY{y)iiRR{r)BB{h) crimson, 



but if the ivory factor is present, the result is magenta (PL VII, fig. 7) : 



YY{y)II{i)RR{T) BB{b) magenta. 



If the Y fJictor is absent, the plant produces dead white flowers (PL VII, 

 fig. 1), though it may be carrying any or all of the remaining factors: 



yyI(i)I(i)R{r)R{r)B{b)B{b) white. 



1 The patch on tliu palate is common to all varieties except white. 



^ In the original publications on Antirrhinum, the factor R was used to denote a 

 tingeing only of anthocj-anin, an additional factor D being present in the fully coloured 

 varieties, but this distinction is not really necessary in the present paper. 



