292 SOME RECENT RESEARCHES IN PLANT PHYSIOLOGY 



being possibly a stage in the reaction. Since equation 1 

 is probably brought about by a respiratory enzyme, it 

 may be seen that the same process involves a reduction 

 of one substance and an oxidation of another. Accord- 

 ingly the result is obtained that an oxidizing enzyme is 

 concerned in the reducing processes leading to the produc- 

 tion of anthocyanin. The writer is of course aware that 

 the peroxidase -system may have nothing to do with the 

 appearance of the pigment, and that, even if it is con- 

 cerned in its formation, the scheme outlined here may be 

 quite erroneous. It is put forward merely as appearing 

 to combine into a coherent whole the results obtained by 

 diverse lines of research. 



PROVISIONAL CLASSIFICATION OF PLANT PIGMENTS. 



Before leaving the very complex subject of plant pig- 

 ments, it may be of interest to quote an outline classifica- 

 tion recently suggested by Keeble, Armstrong, and Jones 

 (1913, 3). Detailed accounts of the plastid pigments may 

 be found in Czapek's " Biochemie der Pflanzen," and in 

 Willstatter and Stoll's " Untersuchungen iiber Chloro- 

 phyll." 



1. Plastid pigments: 



(a) Chlorophyll pigments contain (Mgand) . . C, H, O, N. 



(6) Carrotin contains C, H. 



(c) Xanthophyll (oxidized carrotin) contains C, H, O. 



2. Sap-soluble pigments: 



(a) Yellow. Hydroxyflavone glucosides, or 



derivatives thereof, contain . . . . C, H, O. 



(&) Red e.g., of wallflower. Hydroxyflavone 



glucoside derivatives contain . . . . C, H, O. 



(c) Red and brown e.g., of plum. Sub- 

 stances produced by the oxidation of 

 phenols in presence of amino-acids con- 

 tain C,H, 0,N. 



NOTE. Willstatter and Zechmeister (1914) have since succeeded 

 in synthesizing pelargonidin. 



