112 CAROTINOIDS AND RELATED PIGMENTS 



algae, and expressed the belief that the pure xanthophyll-like phyco- 

 xanthin in Oscillatoria is closely related to, but not identical with, the 

 xanthophyll of higher green plants. 



Sorby (1873) differentiated between phycoxanthin, fucoxanthin and 

 "orange xanthophyll" (carotin) in Oscillatoria. Sorby's phycoxanthin 

 is not identical with the so-called phycoxanthin of brown algse, the 

 pigment now known as fucoxanthin. As described by Sorby phyco- 

 xanthin is practically non-extractable from alcohol by carbon disul- 

 fide, but when dissolved in the latter solvent gives red solutions, 

 which are still pink in great dilution, the absorption bands in this 

 solvent being shifted towards the red end of the spectrum to even a 

 greater extent than those of carotin. The presence of such a pigment 

 in Oscillatoria has not been reported by others, and its relation to the 

 carotinoids remains to be determined. Sorby's fucoxanthin is identi- 

 cal with the fucoxanthin of the brown algae, whose chemical prop- 

 erties have been described. No other investigator has reported the 

 presence of this pigment in the blue-green algce. If Sorby's observa- 

 tions can be substantiated it will show that this pigment is much 

 more universally distributed among the algae than has been hereto- 

 fore regarded. 



Sorby also reported observations regarding the distribution of 

 phycoxanthin, "orange xanthophyll" and fucoxanthin in Oscillatoria 

 with different exposures of the organisms to light, rinding that the 

 more intense the light during growth the more phycoxanthin and 

 "orange xanthophyll" (carotin) they contain and the less fucoxanthin. 



Further evidence regarding the presence of carotin in the blue- 

 green alga? was furnished by Monteverde (1893), who demonstrated 

 carotin in Oscillatoria by the Kraus method. The question of the 

 character of the pigments remaining in the alcohol following the 

 separation between this solvent and petroleum ether was left open 

 by Monteverde. 



That even the lowest forms are abundantly pigmented by carotin 

 has been shown by Zopf (1900) who has described the ease with which 

 carotin crystals can be obtained from Microcystis (Polycystis) flos 

 aqucB Wittr. It is doubtful, however, whether Zopf is justified in re- 

 garding the carotin as a special pigment, and ascribing to it the name 

 polycystin. 



