i68 Plant Pigments [March, 



Keeble, Armstrong and Jones^^ suggest that the higher mem- 

 bers of a flower-color series owe their origin to the presence, with 

 the lower members, of specific substances which, acting as receivers 

 of oxygen, reduce the pigments characteristic of the lower members 

 of the color series, except oxygen, and then become oxidized to 

 other pigments. 



Wheldale^"'^ classifies pigments other than Chlorophyll as follows : 



A. Pigments in Solution in cell-sap. 



(i) Soluble red, purple, blue pigments ( " anthocyanin " ) . 

 Several subclasses. 



(2) Soluble yellow pigments ( " xanthein " ) . Several sub- 

 classes. 



B. Pigments associated with specialised protoplasmic bodies — chro- 



moplastids, the color in this case being usually yellow, 

 orange-yellow, orange or orange-red. Insolubility in 

 water appears to be a constant characteristic of this 

 group. 

 (i) Carotin. 

 (2) Xanthin. 

 A more detailed Classification is that given by Keeble, Arm- 

 strong and Jones, as follows :^^ 

 I. Plastid pigments. 



(a) Chlorophyll pigments, containing C, H, O, N. 



(b) Carotin, containing C, H. 



(c) Xanthophyll (oxidized Carotin), containing C, H, O. 

 IL Sap pigments. 



(a) Yellow, hydroxy-flavone glucosides or their derivatives, 

 containing C, H, O. 



(b) Red products of the action of oxidase on hydroxy-flavone 



(glucoside derivatives containing C, H, O). 



(c) Red and brown substances {e. g., the plum) produced by 

 oxidation of phenols in the presence of amino acids, con- 

 taining C, H, O, N. 



16 Keeble, Armstrong and Jones: Proc. Roy. Soc. London (B), 1914, Ixxxvii, 

 p. 113. 



17 Wheldale : Ibid., 1909, Ixxxi, p. 44. 



18 Keeble, Armstrong and Jones: Ibid., 1914, Ixxxvii, p. 113. 



