Mij:>f> W/ieldale, On the iiatLire of anthocyanin. 141 



III. Yellow flowers containing a so-called xanthe'ic pigment 

 (sometimes in addition a yellow plastid pigment), of which the 

 extract gives a colouration with iron salts; a yellow, orange-yellow, 

 orange or red precipitate with basic lead acetate and similar 

 colourations with acids and alkalis. 



(a) Those giving a green colouration with iron salts : 

 Mesembryanthemum pomeridianmn (yellow)*, Centaurea eriophora 

 (orange-yellow), Centaurea scabiosa (orange-yellow), yellow variety 

 of Chrysanthemum carinatum (orange), Gorydalis lidea (orange- 

 yellow), yellow variety of Dahlia variabilis (red), yellow variety 

 of Helichrysum bracteatum (orange), Tagetes signata (orange), 

 Goronilla glauca (orange), Mirabilis Jalajja (yellow), Primula 

 acaulis (orange). Calceolaria sp. (orange), and Nemesia stru7nosa 

 (yellow). 



(6) Those giving a blue colouration with iron salts : 

 Linaria multipunctata (orange-red) and Linaria vulgaris (orange- 

 red). The following are exceptions in that they do not give the 

 above reactions with iron salts: Coreopsis Drummondii'f (red) and 

 Verbascum Lychinitis (yellow). 



When anthocyanin was present in the genera examined, the 

 reactions given by the usual reagents were diverse, but the more 

 common type of reaction is that given in Class IV., i.e. a green 

 colouration with alkalis, a green precipitate with basic lead acetate 

 and a green or blue colouration with iron salts. It is doubtful 

 whether the blue colouration given by the anthocyanin of many 

 herbaceous genera is in any way similar to the true iron-blueing 

 tannin reaction. Extracts from the flowers of some shrubs, such 

 as red varieties of Rosa, give a true iron-blueing reaction like that 

 of the oak-gall, and this result may be due to admixture of tannin 

 present in the plant. I am inclined to believe that the iron-blueing 

 reaction of the flower extract of herbaceous plants may only be 

 a specific reaction of anthocyanin itself and not an indication 

 of a true tannin nature of this substance. Yet this point of view 

 by no means vitiates the suggestion that this pigment may be an 

 aromatic substance closely allied to the tannins. 



The anthocyanin of Glass IV. is of the purple or purplish-red 

 type. Though the colours of the flowers, from which it is obtained, 

 often differ among themselves, the alcoholic extracts have the 

 common property of being purple or purplish-red in colour. 



IV. Red, purple or blue flowers containing anthocyanin 

 (sometimes in addition plastid pigment), of which the extract 

 gives a green colour with alkalis and a green precipitate with 

 basic lead acetate. 



* Denotes colour given with allialis and basic lead acetate. 

 t Tested only with ferric chloride. 



