1913.] Formation of the Anthocyan Pigments of Plants. 317 



are not destroyed by the former reagent, resume their activity, and colourless 

 chromogen is converted into anthocyan pigment. 



The fact that the colours of the pigments thus produced are identical 

 severally with those of the natural petals, indicates either that chromogens 

 of more than one kind exist in the different colour-varieties of stocks, or 

 — what for our present purpose is nearly the same thing — that one chromogen 

 is present, and associated with it are substances which determine the colora- 

 tion of the oxidised produce of the chromogen. 



The petals of plants such as stocks contain much larger quantities of 

 chromogen than are used in the natural flower. Not only may the original 

 depth of colour be recovered, but the pigment so formed may be removed from 

 the tissues and further instalments of pigment may be produced. Whether 

 the reserves of chromogen contained in the flower occur as such or, as would 

 appear more probable, in the form of prochromogen, we cannot at present say. 



The factor which determines the direction in which the pigment-producing 

 reaction shall go is the amount of active water present in the cells. As the 

 amount of water decreases, the reducing agents of the cell become active and 

 oxydase becomes inert ; as the amount of water increases oxydase action 

 comes into play and the reducing agents are either destroyed, or, if they 

 persist, any action which they exert is masked by the superior and opposed 

 activity of oxydase. The relations may be expressed diagrammatically by 

 the following scheme : — 



f Oxydase "I 

 \+ Water J 

 Chromogen Anthocyan pigment, 



f - Water 

 I Keducing agent 

 ■< 



The occurrence of reducing bodies side by side with oxydases in the 

 anthocyan-containing tissue of plants, the antagonistic relation which obtains 

 between the reducing and oxidising agents of the cell, and the relations 

 which exist between the activities of these agents and the degree of hydra- 

 tion of the cell are calculated to throw light, not only on the phenomena 

 of pigment-formation and pigment-inhibition in plants, but also on others 

 of wider import. Following the clue offered by these experiments we may 

 hope perhaps to advance towards an understanding of the biochemical 

 meanings of activity and latency of seeds, of the enforced and natural 

 awakening of vegetation, and of cognate phenomena. 



A discussion of the foregoing facts in relation with these phenomena lies, 

 however, beyond the scope of the present communication. 



} 



VOL. LXXXVI. — B. 



