184 ANTHOCYANINS AND GENETICS 



In Corchorus capsularis : when deep red-stemmed varieties are 

 crossed with green-stemmed varieties, the colour in stems of F t is less 

 intense (Finlow & Burkill, 572). 



In the cross Datura Tatula, with red stems and purple flowers, by 

 D. Stramonium, with green stems and white flowers, the colour in 

 flowers and stems in Fj is less intense (Saunders, 475). 



In Egyptian cotton, Gossypium : when the variety with a spot on 

 the leaf is crossed with the non-spotted variety, the spot in F a is paler 

 in colour (Balls, 515, 523). 



In Indian cotton : when strains with anthocyanin in the vegetative 

 parts are crossed with green-leaved strains, the colour in leaves and 

 stems in F x is paler (Leake, 561). 



In Linum usitatissimum : a cross between a blue-flowered and a 

 white-flowered variety gave an F x with paler blue flowers than the 

 parent (Tammes, 564). 



On the other hand, in many cases where there are factors producing 

 colour (anthocyanin) no heterozygous forms at all exist, as in Lathyrus 

 and Matthiola. 



Cases, fundamentally different, though giving a similar result to 

 those above, are those in which the type has anthocyanin inhibition 

 by an inhibiting factor, and the variety has lost the inhibitor and 

 produces anthocyanin. When the type is crossed with variety, the Y l 

 is heterozygous for the inhibitor and is less intensely coloured than the 

 parent. Examples of such are the F x from Coreopsis tinctoria with 

 yellow (plastid pigment) flowers and the variety brunnea (anthocyanin 

 on plastids) (de Vries, 474) ; the Fj has paler flowers than brunnea ; also 

 the F x , probably, from the yellow Sunflower by its chestnut-red variety. 



Somewhat similar, though not strictly comparable, is the case in 

 Primula sinensis where whites tinged with anthocyanin are obtained 

 in F x from the cross 'dominant white x fully-coloured variety (Gregory, 

 557). 



In connection with the class mentioned above which is heterozygous 

 for the factor for colour, Antirrhinum offers an interesting illustration. 

 Colour, i.e. anthocyanin, in Antirrhinum is produced by the action of 

 one factor, L, which gives ivory tinged with magenta, but there is no 

 apparent difference in the flower-colour between individuals of the 

 composition LL and LI. In the presence of an additional factor D, 

 a deepening factor, the zygote develops more pigment and is a deeper 

 colour, but the ultimate colour depends on whether the zygote is homo- 

 zygous or heterozygous for L, its condition as regards D having no 



