256 PIGMENTS 



According to Buscalioni and Polacci * anthocyanins may 

 increase the osmotic forces of the cell, but they are careful to 

 point out that they may perform many functions in different 

 plants. 



Wulff considers that the pigment is of value in the absorp- 

 tion of extra radiant energy, and is of great importance in 

 arctic plants, for instance, which live under conditions un- 

 favourable for metabolic activities. 



Combes holds views similar to those of Palladin, that 

 anthocyanin is closely connected with respiration. Jf the sugar 

 content increases the rate of respiration is accelerated, and this 

 leads to the formation of the pigment. 



It may be remarked that most of the above opinions were 

 put forward before the work of Palladin on respiration and the 

 relationships between pigments and enzymic activity appeared. 

 And, in view of this, some of the earlier experiments appear to 

 require reconsideration from Palladin's point of view. 



PHYCOERYTHRIN. 



Phycoerythrin is a red pigment commonly occurring in red 

 sea-weeds, especially when growing in deep water. It has 

 been investigated by Hanson,f on whose account the follow- 

 ing description is based : 



Phycoerythrin is easily soluble in water, giving a rose- 

 coloured solution which exhibits a well-marked orange fluor- 

 esence ; the spectrum shows that the chief absorption is that 

 of the blue-green rays. 



Preparation. 



To prepare a solution of phycoerythrin the red sea- weed, 

 Ceramium rubrum, which is one of the best to use, is washed 

 in ordinary water to free it from sea salts and adhering sand. 

 It is then soaked in distilled water ; in two days most of the 

 pigment will have diffused out. The solution is filtered through 

 glass wool and a few drops of eucalyptus oil adcied as an anti- 

 septic, for putrefaction soon sets in. 



* Buscalioni and Polacci : " Atti. Inst. Bot., Pavia," 1904, II., 8, i, 135. 

 f Hanson : '.' New Phytologist," 1909, 8, 337. 



