1898] COLOURING MATTERS OF FLOWERS 197 



to yield the mysterious green reaction with alkalies and acetate of 

 lead. Everybody who has commenced the study of this subject is 

 both pleased, puzzled, and surprised, by this reaction. There is a 

 peculiarly vivid emerald-green brilliancy about it which is almost 

 unmatchable. I have frequently prepared paracarthamin from rutin 

 and quercetin extracted from plants, but the reactions thereof are 

 incomparable with those yielded by the nature-formed cyanin, whether 

 in petal or leaf. According to Wiesner the colour of the lead salt 

 ought to be really blue, the actual green being caused by an inter- 

 mixture of tannin in the solution ; but experiments with carefully 

 purified tannin show that the colour is actually a dark bluish-green. 

 However, to resume, it would appear that the researches of certain 

 micro-chemists such as Nageli, Wiesner, etc., revealed for the first 

 time the important fact, that certain astringent matters were found 

 in parts of plants which become red or blue, nay even the actual 

 colouring matters seemed to spring up as it were grasped into the 

 very substance of the tannin itself. It was natural, therefore, that 

 Wigand should point out that the chromogen of anthocyan might be 

 regarded as perhaps not tannin, but some modification thereof, which 

 he denoted as cyanogen, ' the transformation depending on a process 

 of oxidation.' This extremely valuable declaration was, however, in 

 a most marked manner left unnoticed in later works, until Lindt 

 detected the relationship anew, and subjoined the conjecture that the 

 production of the red pigment might depend on phloroglucin — a 

 decomposition product of tannin, similarly as the action of vanillin 

 on this phenol takes place, an action which results from the com- 

 bination of two molecules phenol with one molecule aldehyde with 

 elimination of water and production of a red resinous body. Waage, 

 however, in 1890 recognised the fact that the presence of phloro- 

 glucin in a plant was a by no means absolute requirement for the 

 coming forth of a soluble red pigment (anthocyan), since, for instance 

 many Chenopodiaceae are tinged strongly red, though no phloroglucin 

 can be detected therein. It might possibly, of course, happen that on 

 the production of anthocyan a consumption of phloroglucin took 

 place, or perhaps it required a longer time to form in the light than 

 the red matter which was suddenly created thereby in a colourless 

 tissue, and hence in either case it would not be detected ; but then 

 again it may be objected that the metabolism would be so much 

 increased by the action of light that even a wholesale formation or 

 substitution of phloroglucin in the briefest time would be accounted 

 for. Thereupon Waage performed an experiment forthwith on the 

 seeds of buckwheat, which indicated the probability of some though 

 only a slight consumption of phloroglucin accompanying the rapid 

 formation of the red colouration in etiolated seedlings which are 

 suddenly brought into the light. It was also observed that in the 



