196 NATURAL SCIENCE [March 



colouring matters are not formed from chlorophyll, and when Marquart 

 observed that cyanin appeared by its characters and its little 

 stability to approach the paracarthamin obtained by the action of 

 sodium amalgam on quercitrin and quercetin, a discovery that 

 immediately originated a crop of surmises, the ground whereof was, 

 that paracarthamin, similarly as cyanin, was also turned green by 

 weak alkalies and by acetate of lead. Thus, for example, Stein, in a 

 short and pleasant paper to the Jahrh. f. praktischc Chemic for 1863, 

 distinctly avers, that in most red flowers which he examined the red 

 coloming matter appears to be paracarthamin, and this also is the 

 same body which is found in blue flowers ; the blue pigment is none 

 other than the saline (calcium) compound of the red matter. 

 Nachtrag, too, in a note on the ' Natural Occurrence of Paracar- 

 thamin,' concludes, from the behaviour of the red bark of dogwood 

 (Cornus sanguinea) towards alcoholic potash solution agreeing with 

 that of the pigments of dahlia towards the same reagent, that it 

 likewise contains paracarthamin, and he adds, " the red that can be 

 artificially produced from plant-yellow appears, therefore, to be 

 repeatedly present ready formed in the vegetable kingdom." A 

 certain weight of probability was imparted to these views by the 

 fact alluded to by Stein, viz., that quercetin had previously been 

 shown by Kochleder to exist in the flowers of the horse-chestnut, 

 and by the circumstance that in the flowers of Aescvlus pavia, 

 the origin of the red pigment from the yellow can be clearly 

 followed, as this flower when it comes forth from the bud is yellow 

 and only by little and little turns red. If this be really the modus 

 operandi as existing in nature, it would seem to follow that 

 the bright pigments are really reduction-products and not oxidation- 

 products — a consequence which is not usually met with in analogous 

 cases in other departments of biology. It is now pretty clearly ascer- 

 tained that the yellow rutin or quercetin present in flowers does not, on 

 account of the acid sap, impart a yellow colour thereto in the living 

 condition at least, and that the tannic chromogen of the red flowers 

 is really a development product -of this or other intermediate 

 tannoid glucoside. Moreover, it is a fact that certain tannic acids 

 do yield on reduction with HCl and sodium -amalgam a red substance 

 with reactions towards acetate of lead and alkalies similar to those 

 of paracarthamin, but which nevertheless is certainly not the same 

 as the latter body, although these same tannic acids appear to minister 

 all the while as chromogens to the production of extremely vivid 

 and brilliant scarlet and pure blue flower colouring matters. 



The seemingly intimate relationship between paracarthamin and 

 the red and blue pigments having thus by more explicit researches 

 been dissolved, it became necessary for chemists to search for some 

 other body which could possibly be isolated in sufficient purity so as 



