RED PIGMENT OF FLOWERING PLANTS. 407 



physiology of colours and colour bodies, seems to regard 

 these various pigments as identical, stating that the blue 

 and violet pigments are converted by acids to reds ; and the 

 reds by iron sulphate and by sodium phosphate to violet ; 

 by saturation with sodium salts to blue ; by the action of 

 alkalis, a red solution becomes green and neutralisation by 

 any acid revokes the original red. Hansen (4) too, relying 

 on his spectral analyses of red and blue pigments prepared 

 from various members, believes in the identity of the vari- 

 ously coloured pigments. N. J. C. Muller, (5) on the other 

 hand, claims to show, in the case of flowers, a much greater 

 variety of pigments than is generally thought to exist. He 

 examines the substances in question before treatment with 

 special reagents and after the action of sulphuric acid and 

 of potash. By the action of potash on various red pig- 

 ments he obtains a series of derivitive colours, blue, blue- 

 green, yellow, brown and green. Muller does not state, 

 however, how his original solutions are obtained ; and so at 

 present it must be left doubtful as to whether the red and 

 the violet pigments dissolved in the cell sap, or even the 

 reds from different plants, are of the same or of different 

 chemical composition. 



Concernino- the origin of these colourintj; matters, which 

 for convenience may at present be termed collectively 

 anthocyan, our knowledge is a little more exact. In the 

 first place, there seems to be no question that they are /lo^ 

 derived from chlorophyll. For, not only does red -coloured 

 sap occur in the cells of young tissues before chlorophyll 

 is developed, and also in the cells of various phanerogamic 

 parasites (devoid of chlorophyll) as Balanophora, Raffiesia 

 and the Hydnoreae ; but also Hansen (6) describes in the 

 leaf parenchyma of species of aloe, a colourless chromogen 

 which, acted on by water and oxygen, gives rise to a red 

 pigment similar to that contained in many fruits. Like 

 chromogens are probably to be found in many of those 

 colourless underground parts of plants, such as the 

 rhizomes of Dentaria bulbife^-a, Viola sp., etc., which become 

 violet coloured on exposure to light. Wigand (7) has shown 

 that red sap is peculiarly characteristic of tannin-containing 



