306 Miss M. Wheldale and Mr. H. LI. Bassett. 



anthocyanin from the flavone, i.e., that the hydroxyls of the flavones may 

 be protected by sugar, so to speak, and only after hydrolysis can changes 

 take place at these points, there is no very definite evidence as to the 

 number of sugar molecules attached to flavones in the plant. Careful 

 isolation and analysis would be necessary to ascertain the actual condition 

 in the living plant, owing to the great ease with which hydrolysis takes 

 place after death. 



Eed and magenta anthocyanin have been obtained by us from Antirrhinum 

 in a fairly pure state, and certain derivatives have been made. The fact 

 that these, as well as the pigments, are practically amorphous indicates that 

 they probably have very high molecular weights. The lack of melting 

 points in the pigments supports this view. 



In a recent paper Keeble, Armstrong, and Jones* bring forward an 

 hypothesis to explain the loss of colour when coloured petals are treated 

 with strong alcohol, and the subsequent restoration of colour when they 

 are treated with water. 



The phenomena recorded are as follows : — When coloured (anthocyanin) 

 petals of Stocks {Matthiola) are placed in strong alcohol, some pigment passes 

 into solution in the alcohol, which at first is coloured but fairly rapidly 

 becomes colourless. The petals also become colourless though more slowly. 

 When the colourless petals are taken out and placed in water the colour 

 returns ; in hot water the recovery is more rapid. When the extract is 

 filtered from the petals and evaporated to dryness on a water-bath the colour 

 returns to the residue. In addition we have noted that colour returns to 

 the alcoholic filtrate on dilution with water, and this also happens even 

 after evaporation to dryness and taking up again with alcohol. 



The above phenomena are exhibited by most pigments of the anthocyanin 

 class, and have been noted by various authors working on anthocyanin, 

 among whom may be mentioned Hansen,^ MolischJ and Grafe.§ 



The hypothesis brought forward by Keeble, Armstrong, and Jones to 

 explain these phenomena is the following : — The petals contain an oxydase 

 and a reducing agent, which is probably not an enzyme. The oxydase is 

 responsible for the production of anthocyanin from the chromogen, and the 



* Keeble, F., Armstrong, E. F., and Jones, W. N., " The Formation of the Anthocyan 

 Pigments of Plants. Part IV.— The Chromogens," ' Eoy. Soc. Proc.,' 1913, B, vol. 86, 

 p. 308. 



t Hansen, A., 1 Die Farbstoffe der Bliithen und Friichte,' Wiirzburg, 1884. 



% Molisch, H. J., " TJeber amorphes und kristallisiertes Anthokyan," ' Bot. Zeit.,' 

 Leipzig, 1905, vol. 63, p. 145. 



§ Grafe, V., "Studienuber das Anthokyan.— Mittheilung 3," 'Sitzb. Ak. Wiss. Wien,' 

 1911, vol. 120 (1), p. 765. 



