188 ANTHOCYANINS AND GENETICS 



factors M (magenta, dominant to crimson, colour). S (short, dominant 

 to long, style) and G (green, dominant to red, stigma). The MG 

 reduplication is of the form 2:1, the MS of the form 7:1; the secondary 

 reduplication, SG, calculated on the above hypothesis, should be 

 5:3:3:5, and this is fairly near the experimental result. Further 

 confirmation of Trow's hypothesis is also given by results published 

 by Punnett (599) for the Sweet Pea crosses, BEL x bel and BeL x bEl, 

 where B is blue, dominant to red, colour, E erect, dominant to hooded, 

 standard, and L, long, dominant to round, pollen. 



PATTERN IN COLOUR VARIATION 



Most of the following cases have been mentioned in the previous 

 accounts, but they are enumerated again here for the convenience of 

 reference. Pattern generally implies the localisation of pigment . in 

 definite areas. 



Antirrhinum majus. The 'delila' variety may perhaps be regarded 

 as an instance of pattern. For every variety with anthocyanin there 

 is a corresponding ' delila form,' that is one in which the lips are coloured 

 but the tube is ivory; there is always a sharp line of demarcation at 

 the point of union of the tube and lips (Wheldale, 535). 



Arum maculatum. The black spots (anthocyanin) on the leaf are 

 probably due to a Mendelian factor which is dominant to the lack 

 of spots (Colgan, 552). 



Cypripedium (Paphiopedilum). Patterns of spots or stripes (antho- 

 cyanin) may be present. On crossing, there is segregation into striped 

 and spotted; the former appears to be dominant (Hurst, 502). 



Digitalis purpurea. The presence of spots on the inner lower surface 

 of the corolla is bound up with the presence of pigment in the corolla 

 generally. The ground colour of the corolla can be inhibited by an 

 inhibiting factor, but not the spot colour (Keeble, Pellew & Jones, 542). 



Erodium cicutarium. A variety occurs without patches at the base 

 of the petals (de Vries, 565). 



Gentiana punctata. There is a variety in which the dark patches 

 in the flower are absent (de Vries, 565). 



Gossypium. The red anthocyanin 'spot' on the leaf is a Mendelian 

 character, and is less intense in the heterozygous forms. In Indian 

 cotton a red spot on the flower is characteristic of the heterozygote, 

 but an almost completely red flower is characteristic of the homozygote 

 (Balls, 515, 523; Leake, 561). 



Mimulus quinquevulnerus . " Here the dark brown spots vary between 



