THE ANTHOCYAN PIGMENTS 60 1 



taining them in a fairly pure, but amorphous condition, showed 

 that the one (B) was a glucoside of the other (A). He gave 

 analyses and formulae, but these have proved to be incorrect, 

 though the relative amount of glucose present in his glucoside 

 (B) given by him, has proved approximately correct. 



The result of this work of Heise and Glan was to produce a 

 general tendency to consider that the anthocyan pigments "were 

 present in plants both as glucosides and non-glucosides, the 

 former predominating somewhat. Molisch, in 1905, decided in 

 favour of their being glucosides ; but Grafe, who carried out a 

 continuation of Molisch's work on a preparative scale, reverted 

 to the earlier ideas. The results of recent work have definitely 

 proved that in all investigated cases, these pigments occur only 

 as glucosides, the non-glucosides obtained by the above workers 

 being merely the result of hydrolysis during preparation. 



In 1895, Weigert published (Jahrber. der k. k. onol.and pomol., 

 Lehranstalt in Klosterneuburg, 1894-95.) a classification of the 

 anthocyan pigments, thereby completely dispelling the one-pig- 

 ment idea that had so often been brought forward. In this 

 connection a short summary of the views of earlier workers 

 upon this point will not be out of place. Berzelius was not of 

 the opinion that only one anthocyan pigment existed, [whereas 

 Fremy and Cloez considered that all red, violet, and blue flowers 

 contained the same blue pigment (cyanin), its colour having 

 been changed by the conditions prevailing in the various cell 

 saps. Filhol, as also Wigand (Bot. Ztg. 1862, 123), likewise 

 asserted that all red and blue flower colours were produced by 

 different forms of one and the same anthocyan, and Hausen 

 (Die Farbstoffe der Blilten and Friichten, Wurzburg, 1884, p. 8) 

 went still further, being of the opinion that not only all red 

 colours in flowers, but also those in fruits, were due to one 

 and the same pigment. Wiesner (Bot Ztg. 1862, 392,), how- 

 ever, cast considerable doubt upon the identity of all these 

 pigments. 



Weigert, as a result of the comparison of the behaviour of 

 the anthocyan pigments with various reagents, in particular with 

 regard to the colour of their lead salts, and the colour changes 

 that took place on addition of acid or alkali, distinguished two 

 great classes of these compounds ; the first — wine-red group — 

 such as gave blue or blue-green lead salts, and whose acidified 

 solution, on addition of alkali, became blue or blue-green, and a 



