258 PIGMENTS 



Ewart does not think that the pigment is an accidental 

 occurrence in all cases, for in Elodea it is not formed in diffuse 

 light ; on the other hand, in the beetroot it probably has no 

 special function, and may be a waste product of metabolism. 



Stahl also expressed the view that the red colour may 

 protect the plant from the predatory tendencies of herbivorous 

 animals. Such a function is, of course, quite secondary, but 

 may be of use to the plant when the animals have an antipathy 

 to certain hues. Tichler considered that anthocyanin promotes 

 the anabolic processes of the plant. 



Overton agrees with the view of Stahl that the presence of 

 anthocyanin may promote nutritive processes by the absorption 

 of heat. 



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 

 recently been investigated by Hanson,-}- on whose account the 

 following description is based : — 



Phycoerythrin is easily soluble in water, giving a rose- 



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

 t Hanson ; " New Phylologist," igog, 8, 337. 



