SOME RECENT WORK ON PLANT OXIDASES 121 



sally. Bartlett, after a careful investigation into the nature 

 of a water-soluble ammonia-greening anthocyanin, concludes 

 that it is itself a glucoside, and states that the only non- 

 glucosidal ammonia-greening anthocyanin known to him is 

 insoluble in water. This, it may be remarked, is obtained from 

 Althaea. Molisch records the occurrence of anthocyanin in the 

 solid condition, both as amorphous and crystalline aggregates, 

 in many flowers and leaves. Keeble, Armstrong and Jones 

 have shown that the pale yellow sap-colour of the petals of the 

 wallflower is a mixture of hydroxy-flavone glucosides. From 

 this by suitable treatment a red pigment may be obtained, which 

 is not a glucoside. Oxidations of the hydrolysed products of the 

 yellow glucosides by means of oxidase, in presence of amino- 

 acids, result also in the production of pigments. An interesting 

 research by Willstatter and Everest 1 on the blue pigment of 

 cornflowers has just appeared. They have determined that the 

 blue pigment is the potassium salt of an acid (cyanin), which is 

 violet in the free state, whereas the red pigments are combina- 

 tions of this acid with simple organic acids. Thus the occurrence 

 of various shades of colour in the flower is explained. These 

 two authors also believe that all anthocyanins are present in 

 flowers as glucosides. Their paper contains many other points 

 of importance. 



The beautiful changes of colour which many flowers undergo 

 in fading have arrested the attention of both the scientist and 

 the poet. This phenomenon has been employed in a beautiful 

 simile by " A. E." {Collected Poems, p. 9) : 



Its edges foamed with amethyst and rose, 



Withers once more the old blue flower of day : 

 There where the ether like a diamond glows 

 Its petals fade away. 



By means of the use of benzidine and a-naphthol as micro- 

 chemical reagents, Keeble, Armstrong, and Jones have studied 

 the distribution of oxidases in flowers, and have shown that 

 when oxidase and chromogen are both present a white colour 

 may still persist owing to the action of an inhibitor. The 

 removal of the latter by dilute hydrogen cyanide permits of the 

 action of the enzyme on one of the artificial chromogens pre- 



1 Willstatter, R., and Everest, A. E., Liebig's Annalen, 1913, 401, 189 ;' and 

 J.C.S. Dec. 1913, A. i. 1371. 



