154 Miss Wheldale, On the nature of anthocyanin. 



All forms of anthocyanin so far considered (except the pinks 

 of Phlox, Dianthus, Antirrliinum, the pink and scarlet o^ Verbena 

 and the red of Matthiola) have been of the type which may be 

 termed purple and purplish-red, that is, though the flower-colours 

 may be dissimilar, the extracted solution has a purplish tinge and 

 the colouration with alkalis is green. 



The following pink and scarlet colours resemble the red 

 varieties of Dianthus and Matthiola in giving a red or bluish-red 

 colouration or precipitate with basic lead acetate and a full green 

 or some green colour with alkalis : — 

 Pink Impatiens sultani (violet)*. 



„ Begonia-Glorie de Lorraine (greenish). 

 Berries of Berheris vidgaris (unaffected). 

 Red Delphinium cardinale „ 



Scarlet variety of Pentstemon sp. (brownish-red). 

 From the above examples it is apparent that a difference 

 in the reactions with iron salts and with basic lead acetate is 

 frequently associated with the production of an anthocyanin 

 differently coloured, i.e. pink or scarlet, from the more frequent 

 purplish-red form. 



This difference is even more obvious in the following cases 

 of scarlet flowers, with the extract of which both alkalis and basic 

 lead acetate give a red, purplish-red or purple colour: — 

 Scarlet Impatiens Holstii (reddish)*. 

 „ Lobelia cardinalis (unaffected). 

 „ Salvia splendens (red). 

 „ Phaseolus midtiflorus (unaffected). 

 „ Papaver Rhoeas (brown-red). 

 „ Anagallis grwndifiora (red). 

 „ Alonsoa miniata coccinea (unaffected). 

 These colour differences may be regarded as further evidence 

 in favour of the suggestion that purple, purplish-red and some 

 pink forms of anthocyanin are derived from iron-greening chro- 

 mogens. When the latter are absent from the plant the flower 

 colour is of a strikingly different shade. 



The significance of the change from a green to a blue iron- 

 reaction, which so often accompanies a blueing of the anthocyanin, 

 is as yet inexplicable. It is possible that as the oxidation of the 

 anthocyanin progresses, less of the chromogen remains and hence 

 the green iron-reaction of the latter is hidden by the ii'on-reaction 

 of anthocyanin itself. This suggestion, however, hardly fits such 

 cases as those in which the chromogen is present in a quantity 

 sufficient to produce a green colouration with basic lead acetate 

 and with alkalis, though at the same time the iron-reaction is 

 blue. Probably examination of a larger number of genera may 

 * Denotes colour with iron-salts. 



