1908.] 



Flowers with Special Reference to Genetics. 



59 



probably contains xanthin only. Various purples and crimsons are given on 

 the addition of anthocyanin. 



Tropceolacece. 



Tropceolum magus shows the anthocyanin-plastid series. In the pale 

 yellow variety the plastids contain only xanthin, in the deep yellows carotin 

 and xanthin. Anthocyanin may be present in addition at the base of the 

 petals or diffused throughout the flower. Various concentrations of antho- 

 cyanin on pale and deep yellow give orange-red, salmon-red, crimson, etc. 



T. canariense has plastids containing xanthin only. 



T. speciosum contains anthocyanin. 



Violaccw. 



Viola tricolor shows the anthocyanin-plastid series. The deep yellow has 

 plastids containing carotin and xanthin, and in addition a crystalline 

 glucoside, similar to that found in Uschscholtzia. A paler yellow variety 

 appeared to contain the glucoside only. 



Summary of Results. 



1. " Anthocyanin," the term used in connection with the red sap-colour in 

 plants, includes several pigments differing as regards their inheritance, the 

 colours to which they give rise in variation, and their behaviour towards 

 chemical reagents. 



2. The colours of the varieties arising from an " anthocyanic " type may 

 be regarded as components of the original " anthocyanin " ; the type, 

 conversely, may be supposed to lose its components (which are expressible 

 as Mendelian factors) in succession, thus giving rise to a series of colour 

 A^ariations. 



3. Broadly speaking, there are two series of colour variations, one con- 

 taining a " xantheic " derivative, as, for example, in Antirrhinum ?najus, the 

 other no such derivative, as in Lathyrus odoratus. 



4. Albinism, in the first series, is a lack of both " anthocyanin " and 

 " xanthein " ; in the second series of " anthocyanin " only. 



5. " Xanthein," a term used in connection with yellow sap-colour, includes 

 several different pigments. This is to be expected if the view that " xanthein " 

 is a derivative of " anthocyanin " be accepted. 



6. There is evidence, as far as investigations have gone, of a correlation 

 between the behaviour of pigments in genetics and their reactions towards 

 chemical reagents. 



7. In the case of plastid pigments, the type may contain carotin, 

 xanthin, or both. Varieties arise in some cases from loss of power to 



