170 ANTHOCYANINS AND GENETICS 



R are the factors for colour, B modifies the blue-red class to the purple 

 class, D causes dilution in colour and X the difference between the 

 pure and dull, or impure, colour: 



CRBDX pale purple. 



CRBX deep purple. 



ORB plum. 



CRDX pale red (rose). 



CRX deep red (carmine, crimson). 



CR copper. 



C white. 



R white. 



In some families, other varieties, such as terra-cotta, flesh and 

 lilac, appear in addition, but, apart from the fact that they are recessive 

 to crimson and purple, their relationship to each other and to the 

 other colours is not clear at present. As we see from the table, indivi- 

 duals without either C or R are white; thus white can carry every 

 factor and combination of factors, except C and R simultaneously. 

 Many of the above results have been confirmed by Tschermak (590). 

 Mirabilis Jalapa. Correns (482, 497, 537) published the first work 

 on the colour-inheritance in this genus. He used several varieties, 

 white, yellow and 'red.' In F x he obtained a 'rose' by crossing white 

 x yellow, but as he did not realise the existence of heterozygous forms 

 (see below), he was unable to solve successfully his results in the F 2 

 generation. 



Baur (517) made crosses with two varieties, and obtained a hetero- 

 zygous form in Fj, but his results are similar to those of Marryat (533) 

 to whom we owe the bulk of our knowledge on the inheritance of flower- 

 colour in Mirabilis. The work of the latter author leads to the following 

 conclusions : 



We must suppose that the original type had crimson flowers. Loss 

 of a factor for anthocyanin production from crimson gives a variety 

 with yellow flowers free from anthocyanin. Further loss of a factor 

 produces white, an albino both as regards red and yellow pigment. 

 The peculiar interest of Mirabilis (among other points) is centred in 

 the occurrence of heterozygous forms which may be best represented 

 by the following scheme: 



CCMM crimson. 



CcMM magenta. 



CcMm magenta rose. 



CCMm orange red. 



