356 PIGMENTS 



and degrades them to yellow and red light of just those wave- 

 lengths which the chlorophyll can absorb. 



PHYCOPHAEIN. 



As is well known, a brown colouring matter may be 

 extracted by water from the Phaeophycese and other brown 

 Algae. Hitherto this has generally been considered to be 

 due to the presence within the cells of a definite colouring 

 matter of a protein nature. According, however, to the work 

 of Molisch * and Tswett.f this is not the case. The brown 

 colouring matter is really due to post-mortem changes, the 

 oxidation of a water-soluble chromogen. An extract pre- 

 pared with distilled water is at first colourless, but will turn 

 yellow if the solution is made alkaline in reaction, e.g. by tap 

 water, and finally brown owing to oxidation. If the reaction 

 be made acid decolorization will result. With regard to the 

 chemistry of this substance little, if anything, is known. 



PHYCOCYANIN. 



Phycocyanin is a generic term % and includes several blue 

 pigments characteristic of the Cyanophyceas but not neces- 

 sarily restricted to this group, for Kylin and Rodio § have 

 found phycocyanin to be associated with phycoerythrin in 

 - Ceramium, Chondrus, and other members of the Rhodophyceae. 



Phycocyanin is soluble in water, giving a blue solution 

 which exhibits a carmine fluorescence. Its absorption spec- 

 trum shows one or two bands in the orange-red. 



Preparatio?i. 



To prepare phycocyanin, Molisch || recommends Oscillaria 

 leptotricha ; the plants are rapidly washed with distilled water 

 and placed in a beaker with enough distilled water to 

 cover them completely. A little carbon bisulphide is added 



* Molisch : " Bot. Ztg.," 1894, 52, 181 ; 1895, 53, 131 ; 1905, 63, 131. 

 t Tswett : " Ber. deut. bot. Gesells.," 1906, 24, 235. 

 J Molisch : " Sitz. Kais. Akad. Wiss. Wien." 1906, 115, [i], 795- 

 Kylin : " Zeit. physiol. Chem.," 1912, 76, 396. 

 § Rodio : loc. cit. 

 II Molisch : " Bot. Ztg.," 1905, 63, 159. 



