102 CAROTINOIDS AND RELATED PIGMENTS 



solved was readily re-extracted from the solution by 80 per cent 

 alcohol, and its solubility in petroleum ether was the only point of 

 difference observed between the two xanthophylls. Spectroscopic and 

 adsorption properties were not examined. Both xanthophylls turned 

 green and then blue on addition of acids to their alcoholic solutions 

 and alkali restored the yellow color. This property is characteristic 

 of Tswett's xanthophyll (5 of higher plants, as pointed out in the pre- 

 ceding chapter. The reaction also resembles the color reaction of 

 fucoxanthin with acids. Kylin, himself (1912), suggests this in a foot- 

 note of the report of his study of the pigments of the brown algae, but 

 was unable to decide whether the color reaction was due to traces of 

 brown algae and diatoms present with his material, or to the actual 

 presence of fucoxanthin in the red algae. It is doubtful whether 

 Kylin really effected a separation of distinct pigments in his xantho- 

 phyll fractions. It is not at all unlikely that the RhodophycecB con- 

 tain some fucoxanthin. A spectroscopic and chromatographic analysis 

 of the xanthophylls of the red algae as well as an application of the 

 modified Kraus procedure for separating fucoxanthin from the other 

 earotinoids would be helpful in deciding whether the color reaction 

 observed by Kylin was due to fucoxanthin or to a xanthophyll of the 

 (3 type. 



Van Wisselingh (1915) has recently demonstrated earotinoids in 

 two species of red algae using both the Molisch and the acid micro- 

 crystallization method. 



The Chorales. This class of algae, commonly known as the stone- 

 worts, have the interesting property of depositing calcium from the 

 waters in which they thrive, from which they derive their popular 

 name. Only two genera are known, namely, Chara and Xitella. Both 

 Tammes (1900) and Kohl (1902) were successful in showing earo- 

 tinoids to be present in Chara fragilis, using the Molisch method. 

 The same result was obtained by van Wisselingh (1915) on Nitella 

 spores. The evidence points to the presence of earotinoids in the 

 stoneworts, but nothing further is known regarding their character. 



The Chlorophyceae. The so-called green algae constitute one of the 

 largest and most important classes of lower plants. They are found 

 in both fresh and salt water, but the former predominate. The cells 

 as a rule contain chloroplastids which makes the question of the types 

 of plastid pigments present an important one. The feature which 

 has especially attracted attention, however, is the fact that the spores 



