1908.] 



Floivers with Special Reference to Genetics. 



51 



Albinism. 



It has been suggested that there are two forms of anthocyanin giving 

 respectively two colour series, one containing a yellow xantheic variety, the 

 other not. Whites occur in both, and it seems probable that the term 

 albinism should be used in a different sense when applied to each of the 

 two series. 



The extract from most white flowers (also from flowers coloured only with 

 plastid pigments, when these have been removed), gives a canary colour with 

 strong acids and alkalis, as stated previously. Without exception, as far as 

 observations have gone, whites of genera having no yellow sap type, have 

 given this yellow colour-reaction. These whites may, without hesitation, 

 be declared to be recessive to the red-purple-blue types, and they are albinos 

 as regards anthocyanin. 



On the other hand, in the case of Antirrhinum, Azalea, and Phlox 

 Drummondii* belonging to the series giving yellow sap-colour, whites exist 

 which do not give the same yellow colour-reaction. Moreover, these whites 

 are recessive to yellow in Antirrhinum and Phlox, and are albinos as regards 

 both anthocyanin and xanthein. It is the ivory in this series which contains 

 the glucoside-like body, and gives the yellow colour-reaction. 



Whites giving no colour-reaction have not yet been observed in the other 

 genera mentioned in the anthocyanic-xantheie series, though relatively few 

 types have been examined. It is possible that the true albino, as con- 

 trasted with ivory, is rare in commercial samples, since the albino type in 

 Antirrhinum and Phlox has been found to set poor seed unless fertilised 

 artificially. 



What appears at first an exception to this view is the case of Mirabilis 

 Jalapa. Here we find a range of colour similar to that in Antirrhinum, i.e., 

 shades of magenta and crimson, together with deep and pale yellow and 

 white. The white (when it does not carry a reddening factor) is recessive 

 to yeUow,t and yet gives a colour- reaction with ammonia, etc. The 

 explanation lies in the fact that both the yellow and red pigments in 

 Mirabilis (see p. 50) are of an entirely different nature from those 

 in Antirrhinum and Phlox. Tor the same reason, the inheritance in 

 Portulaca grandiflora will, if worked out, doubtless prove to be similar to 

 Mirabilis. 



Shull(lO) also gives the case of Vcrbascum Blattaria, in which a very 



* I am indebted to Miss Killby for the information that in Phlox Drummondii the 

 ivory type may throw both the yellow and the albino. 



t I am indebted to Miss Marryat for this information from results obtained in cross- 

 breeding of Mirabilis. 



E 2 



