v] Reversion in Orchids 97 



been self-fertilised and gave albinos only, as must be ex- 

 pected. Lawrenceanum Hyeanum when selfed, gave 1 4 

 albinos, but in addition, one coloured plant, which Mr Cook- 

 son tells me cannot be thought to have resulted from error. 

 Such an occurrence is as yet unaccountable, but otherwise 

 all is clear. 



In addition to the cases given above there are many in 

 which C. insigne Sanderianum and insigne Sanderae were 

 used, but Mr Hurst tells me that of these the latter is 

 certainly a tinged type, while the former has some dark 

 hairs on its petals which may contain sap-colour. Some of 

 the crosses with these types gave reversionary offspring, 

 and others gave various whites. 



The genus Cattleya provides another list of comparable 

 cases. For instance 



C. Mossiae Wagenerix C. Gaskelliana alba gave 4 albinos 



(Hye). 



,, x C. intermedia alba gave 14 albinos 



(Holford). 



C. Schroderae alba x C. intermedia alba gave coloured 



offspring (Cookson). 



C. Gaskelliana alba x C.Harrisonianaalba gave 4 coloured 



plants (Thwaites). 



,, ,, x C. Warneri alba gave 5 albinos and 



2 coloured plants (Peeters). 



From these statements it may with great probability be 

 inferred that the albinism of Mossiae Wageneri, Gaskelliana 

 alba and intermedia alba is due to the absence of one factor 

 (say C] ; that in Harrisoniana alba and Schroderae alba it 

 is the other complementary factor which is wanting (say K] ; 

 and that Warneri alba is heterozygous for the presence of 

 one of them (being Rr, on this scheme). It is to be hoped 

 that some Orchid grower will make the various unknown 

 combinations and extend the series. 



There are, besides the cases enumerated, many instances 

 in Cypripedium, Cattleya, and other genera, of various 

 tinged types breeding true when self-fertilised and giving 

 reversionary coloured offspring when crossed. 



B. H. 7 



