248 PIGMENTS 



Evvart cites his observations on Elodea against Stahl's view, 

 and remarks that " since the plants \Elodea\ are submerged, it 

 cannot possibly be for the purpose of increasing what is non- 

 existent, i.e. transpiration, nor can it perceptibly raise the tem- 

 perature of a submerged plant ". The first argument may no 

 longer be valid, for it appears that a transpiration current may 

 exist in submerged aquatic plants.* 



Ewart believes that anthocyan is to protect the chlorophyll 

 against the action of too strong light. He gives experimental 

 data in support of his view, and cites the observations of 

 Schrdder and Klebs to the effect that the pigment is of im- 

 portance in protecting the chlorophyll in Hieviatococcus and 

 the resting spores of many Algae. 



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 anthocyan promotes 

 the anabolic processes of the plant. 



Overton agrees with the view of Stahl that the presence of 

 anthocyan may promote nutritive processes by the absorption 

 of heat. 



According to Buscalioni and Polacci f anthocyans may in- 

 crease 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 

 anthocyan is closely connected with respiration. If the sugar 

 content increases the rate of respiration is accelerated, and this 

 leads to the formation of the pigment. 



* See Thoday and Sykes : " Ann. Bot.," 1909, 23, 635. 



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



