1899] COLOURING MATTERS OF FLOWERS 147 



ordinary red or blue flowers which are coloured green by dilute alkalis. 

 Now, it would appear that the majority of flowers contain either rutin 

 or an iron-greening tannin, but a select few, including Fuchsia, Pelar- 

 gonium, Paeonia, and Camellia, undoubtedly contain an iron- 

 blueing tannin which is no other than gallo-tannin mixed probably in 

 some older specimens with a small quantity of gallic or ellagic acid. 

 The ordinary pink rose contains only a highly phloroglucin-bearing 

 tannin common to the whole order to which the queen of flowers 

 belongs ; but in certain garden varieties, wherein the petals have 

 immensely developed with full expansion of parts and profound depth 

 of coloration, a small proportion of gallic acid has doubtless managed 

 to find entrance into the cells of the corolla. In fact, Filhol, Rochleder, 

 and others found gallic acid as a constituent in the well-preserved 

 and intensely purplish crimson cones of the officinal flores Posae 

 rubrae ; and similar remarks will apply to the case of Polygonum 

 orientale. 



The residue of the flowers in the foregoing list belong, it will be 

 observed, to the orders Solanaceae, Plumbaginaceae, Labiatae, Com- 

 positae, and Leguminosae, all of which are distinguished by the 

 absence of free phloroglucin, a fact which affords an insurmountable 

 presumption that the tannic chromogen is of a character distinct from 

 that with which we have just dealt. All who have had some experi- 

 ence in the chemistry of herbaceous plants are fully aware that they 

 are brimful of quercetin in the form of rutin, etc., which, however, of 

 itself fails as a basis for brilliant colorific effects, but may, nevertheless, 

 by further de-assimilation develop into tannins which, in the special 

 instances now under review, belong to the distinctively iron-greening 

 class. The question which is now started and remains to be discussed 

 is, whether this iron-greening tannin is adequate to discharge the 

 function of a chromogen competent to evolve a pure blue flower ? 



All the genera mentioned are, with the exception of Frythrina, 

 capable of producing a blue or purple flower in some of their specific 

 forms. Fuchsia, Plumbago, Lycium, and Salvia produce one or more 

 pure blue efflorescences ; while Pelargonium, Phaseolus, Echinacea, 

 Lmpatiens, Polygonum, Camellia, Paeonia, and Posa produce purples 

 more or less deep and frequently approaching deep blue. Of all these, 

 Fuchsia, Plumbago, Pelargonium, Lycium, Polygonum, Camellia, Paeonia, 

 and Rosa contain either an iron-blueint!' tannin or gallic acid in small 

 quantity, and it is the colouring matter of just these flowers which is 

 most distinctively blued by ammonia vapour or solution. In point of 

 fact, I think it must needs be concluded that in all these instances it 

 is the gallic acid resulting from the oxidation of gallo-tannin or of 

 some nearly allied benzene derivative, which is solely responsible for 

 the blue more or less pure and clear which they so beautifully display. 

 Rosa and Polygonum are exceptional, inasmuch as they are genera 

 which contain a highly phlobaphenic tannin, i.e. a chromogen which 



