PHYCOERYTHRIN 353 



with magnesium, a pale red colour was produced ; they 

 conclude that the young buds contained flavonols which would 

 have developed anthocyanin by reduction of the flavonol in 

 the course of their development. 



There are, in fact, two schools of thought ; Everest, 

 Combes, and Costantin * consider that the anthocyanins are 

 reduction products of fiavones, whilst Noack, Jonesco, Whel- 

 dale, and others, f consider them to be oxidation products of 

 glucosidal flavones. Purely chemical evidence shows that 

 anthocyanin production from a given flavonol proceeds by 

 reduction, but chemical proof of the relationship between the 

 flavonols and anthocyanins occurring together in the same 

 tissues has not as yet been provided. It is possible that the 

 anthocyanin in a given plant material might actually contain 

 a greater number of hydroxyl groups than the flavonol ac- 

 companying it, so that while the conversion of the flavonol 

 into the corresponding anthocyanin would result from re- 

 duction, the introduction of an increased number of hydroxyl 

 groups would nevertheless involve oxidation, so that both 

 schools of thought would be justified. 



PHYCOERYTHRIN. 



Phycoerythrin is a red pigment commonly occurring in 

 red sea-weeds, associated with the chlorophyll and carotin 

 in the chloroplasts. It has been investigated more particularly 

 by Hanson, J Molisch,§ and Rodio.|| 



Phycoerythrin is soluble in water, giving a rose-coloured 

 solution which exhibits a well-marked orange fluorescence ; 

 the spectrum shows three absorption bands in the green, the 

 exact positions varying with different species. Freshly pre- 

 pared aqueous solutions will yield crystals on evaporation 

 and, according to Rodio |! the addition of ammonium sulphate 

 hastens the formation of hexagonal prisms or tablets. 



* Costantin : " Ann. Sci. Nat. Bot.," 1919, x., I, 38. 



t See Kozlowski : " Compt. rend.," 1921, 173, 855. 



{ Hanson : " New Phytologist," 1909. 8, 337. 



§ Molisch : " Bot. Ztg.," 1894, 52, 177. 



II Rodio : " Atti. Accad. Lincei," 1925, vi., i, 188. 



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