146 P. Q. KEEGAN [February 



Meanwhile, however, the remarkable differences which are observ- 

 able in red and blue flowers and their colouring principles towards 

 certain reagents, especially dilute ammonia, or ammonia vapours with 

 or without the presence of added acids, still continued to excite com- 

 ment and acute controversy. So far back as the year 1824 Macaire 

 of Geneva, having noticed that a red infusion of Viola odorata, when 

 mixed with a vegetable alkaloid, such as quinine or strychnine, gradu- 

 ally retakes the natural blue tint of this flower, suspected that its 

 colour is owing to a combination of its chromule with an alkali. In 

 1825 Schubler and Frank testified that the infusion of Funkia ovata 

 treated with an acid and then with an alkali may present in the same 

 vessel all the colours of the spectrum. De Candolle was perfectly 

 aware, in 1832, that the infusion of certain red flowers which have 

 been acidified assume a blue colour when treated with alkalis, and, on 

 the other hand, that the acidified infusions of blue flowers do not 

 reassume their original colour when similarly treated. Fremy and 

 Cloez asserted that anthocyan w T as reddened by acids and greened by 

 alkalis. Wigand stated that the colouring matter dissolved in acid 

 cell saps became by alkalis first blue and then green. Wiesner, on 

 the other hand, stoutly maintained that anthocyan as such or in itself 

 was always blued by alkalis and never greened : it is only when it is 

 present along with a substance which is coloured yellow by alkalis 

 that it passes by the latter body into green, which thus arises as a 

 mixed coloration. In 1867 Naegeli and Schwendener again asserted 

 that anthocyan is blued by alkalis and then passes into green ; and 

 Sacchse, in 1887, expressed concurrence with this view. All this 

 diversity of opinion concerning a matter which, one might imagine, is 

 capable of being settled once and for all by the application of definite 

 tests, would undoubtedly never have come to pass if there had not 

 been " something in it," as they say. The remainder of this paper 

 will be devoted to an attempt to explain precisely what this mysterious 

 " something " is. 



In the first place, it will be advisable to enumerate at least 

 some of those flowers whose colouring matters are known to be 

 blued by ammonia vapour and by a dilute solution of ammonia. The 

 following list comprises some of the most notable examples : — Fuchsia, 

 Pelargonium sp., Plumbago, blue sp., Lycium barbarum, Phaseolus 

 multijlorus, Erythrina crista-galli, Echinacea scrotina, Impaticns balsa- 

 mina, Salvia splcndens, Polygonum orientale, Camellia, Paeony, and deep- 

 red garden Eose (acidified alcoholic extracts). There are doubtless 

 many more, but the study of these may suffice to throw some light on 

 the subject. Assuming what has been abundantly proved, viz., that 

 tannin constitutes the chromogen of the red and blue floral pigments, 

 and that tannin is not a homogeneous chemical compound, but em- 

 braces many varieties, we must ascertain if there exists any kind of 

 tannin in the aforesaid flowers different from that which occurs in the 



