PHYCOCYANIN 



357 



and the preparation is allowed to stand for twenty-four hours. 

 The deep indigo solution is then filtered off and ammonium 

 sulphate added in quantity insufficient to cause precipitation ; 

 on allowing the mixture to evaporate in air in a dark place, 

 crystals of phycocyanin will be deposited. 



Little is known of its chemical constitution ; it is of a 

 protein nature and its physical properties resemble those of 

 phycoerythrin. 



With regard to the physiological significance of these pig- 

 ments of the Algae, the work of Gaidukow * and others on 

 complementary chromatic adaptation may be consulted. 



* Gaidukow : " Ber. deut. bot. Gesells.," 1903. 21, 484, 517 ; 1906. 24, 

 I, 23. Richter : id., 1912, 30, 280. Boresch : id., 1919, 37, 25; 1921. 

 39, 93. Harder : " Zeit. bot.," 1923, 15, 305. 



