vui] Black Fruits 135 



pollen of Turnips is carried by insects to the Swedes, the 

 hybrid thus produced will be white-fleshed, and consequently 

 attract attention, spoiling the uniformity of the crop. But 

 as the white of the Turnip is a dominant, no visible effect 

 is produced even though Swede pollen is brought by the 

 insects to the Turnip flowers, for F^ is white. In F z of 

 course yellow Turnips would appear^, but as the roots are 

 almost always eaten off, this result is scarcely ever reached 

 by the farmer. 



It might be expected perhaps that the blue and purple 

 colours in flowers would always be dominant to the reds, 

 but this is not so. In Stocks, Sweet Peas, Peas, and Salvia 

 the purples are dominant. Probably the same is true for 

 the blues of Delphinium, Cineraria and a good many more, 

 but when we come to Primula Sinensis we find blue a 

 recessive to the reds and magentas. Doubtless the chemistry 

 of the blue pigment is there quite different. 



In Solanum and Atropa black fruit is dominant to the 

 yellow fruit, but in Bryonia the red fruit of B. dioica is 

 dominant to the black fruit of B. alba. This paradox has 

 been elucidated satisfactorily by Miss Wheldale. She tells 

 me that the nature of the distinction between the two types 

 is quite clear. In Atropa the black colour is due to the 

 presence of a dark purple anthocyanin which like other 

 pigments of the same kind is dominant to its absence. In 

 Bryonia alba the black colour is caused by the presence of 

 a little carotin in plastids, together with green chlorophyll 

 undecomposed. In the red-berried Bryonia dioica the 

 chlorophyll is decomposed (just as it is in the cotyledons of 

 yellow-seeded Peas) and much carotin is present. Conse- 

 quently, as may be expected, the presence of the decomposer 

 of the chlorophyll is a dominant, as also is the abundant 

 development of the carotin, and thus the black colour of the 

 fruits is recessive to red. 



In Rabbits, as has been stated above, yellow is a reces- 

 sive to black, while in Mice it is a dominant. 



The yellow varieties of many red Lepidoptera (Zygaena, 

 Arctia, &c.) are presumably recessivef, and the same is 



* From Mr Button's experiments (262) it seems however that F^ is 

 sterile. 



t Proved for Callimorpha dominula. See p. 44- 



