Varietäten, etc. — Physiologie. 69 



later papers in which the Constitution of a number of anthocyanins 

 in addition to cyanidin (of cornflower) is claimed to have been 

 determined. 



Bringing Willstätter's views to bear upon Mendelian factors 

 for flower colour, the following interpretalions are arrived at. 



1) The chromogens of the pigments are flavones and the factor 

 for colour is the power to bring about a simple reduction of the 

 flavone, accompanied by other changes. 2) If the cell sap is neu- 

 tral, the anthocyanin has the structure of an inner oxonium salt 

 and is purple. 3) A reddening factor is one which produces an acid 

 cell sap leading to the formation of a red, acid oxonium salt: a 

 bluing factor is one which produces an alkaline cell sap with for- 

 mation of an alkaline salt. 



Except that anthocyanins are derived from flavones, the author's 

 results, in the case of Antirrliinum, are not in agreement with the 

 above scheme of Will stätter. 



In this species there is no doubt that the chromogen is the 

 flavone apigenin. The author found anthocyanin from Antirrhinum 

 to contain a greater instead of a less percentage of ox5^gen than 

 apigenin. Moreover, the artificial red product prepared from apige- 

 nin by reduction does not give the qualitative reactions nor has it 

 the percentage composition of the natural anthocj^anisn. 



The anthocyanins of Antirrhinum were not obtained in crystal- 

 line form, but their purity was guaranteed by the concordance of 

 analyses when pigments were prepared from different sources. Also 

 the products analysed were the pigments themselves, not the hydro- 

 chloric acid salts. The author does not regard the production from 

 quercetin, by reduction, of a very small quantity of a substance 

 claimed to be identical with cyanidin a convincing reason for regar- 

 ding the natural process of pigment formation as one of reduction. 

 The important point is whether cyanidin is formed from quercetin 

 &c. in the living plant. Further evidence is needed of the con- 

 nection between anthocyanin and flavone in the same plant, and 

 between the natural anthocyanin and the artificial pigment prepared 

 from the same flavone, Only in Antirrhinimi are such relations 

 known and they are not so far in accordance with the reduction 

 hypothesis. 



The author insists further on the necessity of distinguishing 

 between reactions that occur 'in vitro' and in the living cell. 



W. Neilson Jones. 



Jörgensen, I. and F. Kidd. Some photochemical experiments 

 with pure Chlorophyll and their bearing on theories 

 of carbon assimilation. (Proc. Roy. Soc. LXXXIX 617. p. 

 342—361. 1916.) 



The assertion is made that the theories of action of Chloro- 

 phyll in photosynthesis formulated by Wager and also by Ewart 

 were based upon experiments made with impure Chlorophyll. 

 When similar experiments were repeated with Chlorophyll extrac- 

 ted and purified until exhibiting all the known properties of the 

 pure pigment as given by Willstätter, the results of these 

 workers could not be substantiated. No absorption of COo by pure 

 Chlorophyll was detected: Formaldehyde was not produced in any 

 quantity during the bleaching of Chlorophyll in oxygen, but after 

 the bleaching was completed it was formed in amounts large 



