122 CAROTINOIDS AND RELATED PIGMENTS 



ment production in the two last mentioned species of bacteria, states 

 that M. Erythromyxa produces a yellow water-soluble pigment in 

 addition to the red lipochrome. 



Summary 



Our knowledge is practically complete regarding the character and 

 distribution of the carotinoids among certain classes of algae, par- 

 ticularly the brown and red sea-weeds. 



Fresh brow r n sea-weeds owe their olive-brown tint to the special 

 algae carotinoid, fucoxanthin, discovered by Rosanoff (1867) and 

 Millardct (1869), and finally classified definitely as a carotinoid by 

 Willstatter and Page (1914). The relation of this pigment to carotin 

 is shown by the empirical formula C 40 H 56 6 . The characteristic prop- 

 erties of the pigment are described in detail in the text. 



Brown sea-weeds also contain carotin and xanthophyll. The exact 

 relation of this xanthophyll to the xanthophylls of higher plants has 

 not been definitely settled. 



Dried brown sea-weeds owe their color to phycophiiin, a post- 

 mortal oxidation product of colorless chromogens present in the 

 fresh plants. The carotinoids are still present, but the phycophain 

 interferes greatly with their isolation and study. 



The principal pigment of red sea-weeds is phycoerythrin, which is 

 not a carotinoid. Carotin and xanthophyll, however, are present in 

 these plants. There are some indications that the xanthophyll is the 

 xanthophyll (3 which characterizes higher plants. There is a possi- 

 bility, als$ that fucoxanthin is present in the red algae. 



Carotinoids are present in the stone worts, but nothing is known 

 of their nature. 



Carotin and xanthophyll are present in the green algae, the amount 

 of each present in certain species having been determined by Will- 

 statter and Page. The red pigment of the so-called blood algae clas- 

 sified among this family, appears to be related to the carotinoids, but 

 its exact relation remains to be determined. 



Carotin appears to be the principal carotinoid present in the di- 

 atoms. There is a possibility, also, that xanthophylls and fucoxan- 

 thin are present, a phase of the pigmentation of the siliceous algae 

 which deserves further study. 



Our knowledge is indefinite regarding the carotinoids occurring in 

 the Peridiniales, although the indications are that a xanthophyll-like 



