Further experiments on inheritance in sweet peas and stocks: preliminary account

Later results have provided expression which include many of the peculiar phenomena of inheritance already witnessed in sweet peas and stocks. In sweet peas we have shown that purples may occur as a “reversion”, from the cross between two whites, one having long pollen grains, the other round. Similarly in stocks, white glabrous × cream glabrous gives “reversionary ” F1 purple hoary. (In both cases the parents are whites,i. e . free from sap-colour, for cream is due to yellow plastids, recessive to colourless plastides.) The appearance of coloured flowers is due to the simultaneous presence in the zygote of two factors, belonging to distinct allelomorphic pairs, which may be spoken of as C,c , and R,r , the large letter denoting presence, the small letter the absence of the particular factor. Hoariness of stocks is similarly due to the coexistence of two other factors, and the presence of either of these factors is also allelomorphic to its absence. These two pairs are spoken of as H,h and K,k . But, though H and K may both be present, no hoariness is produced unless C and R the colour-factors, are also both present. For the actual developement of hoariness four factors are thus required. The existence of white-flowered hoary plants creates a difficulty; but whiteincana is evidently a coloured form in reality, for its flowers tinge on fading, and its embryo has the deep-green colour characteristic of purple varieties. Apart from breeding-tests, however, white hoaryBromptons show no visible indication of colour, and as yet they constitute a marked exception.