612 SCIENCE PROGRESS 



addition of one molecule of water per molecule ol pigment, 

 which observation is in complete agreement with the scheme 

 (see p. 610) put forward by Everest in the paper mentioned 

 above, and indeed, Willstatter concludes that such of the 

 anthocyans as are 7 pyrone derivatives should be produced 

 by the reduction of flavonols. 1 



It is interesting to note that in the cornflower, and in the 

 rose (gallica), the same pigment, cyanidin, and combined with 

 the same amount of glucose (2 molecules) is present, and, more- 

 over, in the cranberry the pigment is cyanidin combined with 

 but one molecule of glucose. The delphinium pigment is the 

 most complex, yielding on hydrolysis one molecule delphinidin, 

 two molecules glucose, and two molecules p-oxy-benzoic acid. 



There doubtless remains much work to be done in this field 

 of research, but the time has at last arrived when one may 

 speak with certainty of the structure of many of the members 

 of this beautiful series of pigments, and, moreover, as the flavonol 

 derivatives have been synthesised by Kostanecki, the production 

 of anthocyans from them, as mentioned above, completes the 

 synthesis of at least one type, and, in addition, it may well be 

 expected that these great advances in our knowledge of the 

 chemistry of these pigments will materially assist in the elucida- 

 tion of the processes whereby they are formed in the tissues of 

 the living plant. 



1 Although his evidence brought him to support the structural formula previously 

 put forward by Everest for the Anthocyan pigments, Willstatter, in the above- 

 mentioned paper, denied that Everest's pigments were true Anthocyans. In a 

 paper published since the present article was written (Sitzber. der k. Akad. Wiss. 

 Berlin, 1914, 769-77) Willstatter, having repeated Everest's work, withdraws 

 his criticism, and admits that by the reduction of quercetin, a pigment identical in 

 every respect with natural Cyanidin (the pigment of the cornflower, rose, and 

 cranberry) is obtained. Thus the crowning feature in this field of research— the 

 complete synthesis of these pigments— receives confirmation from an independent 

 source. 



