60 CAROTINOIDS AND RELATED PIGMENTS 



pigment because he first isolated it from arbor vitse (Thuja oricn- 

 talis). The pigment is described by Tswett as being ruby red in car- 

 bon disulfide, rose in alcohol and yellow in petroleum ether. It is not 

 adsorbed to any extent by CaCO. ( from petroleum ether or CS 2 solu- 

 tion, but is almost wholly hypophasic in the separation between petro- 

 leum ether and 80 per cent alcohol. Tswett's pigment showed three 

 absorption bands in petroleum ether and- four in carbon disulfide. 



Spectroscopically the pigment differs from any previously known 

 carotinoid, but Tswett's classification of the pigment as a carotin is 

 subject to the same criticism as his classification of the autumn yellow 

 pigments as xanthophylls. It has already been pointed out that chemi- 

 cal composition, not color and colloidal and other physical and 

 physico-chemical properties, must be the correct basis for the classi- 

 fication of carotinoids. The hypophasic relations of thujorhordin in 

 the Kraus separation would classify it as a xanthophyll. Monteverde 

 and Lubimcnko (19131)) and Lubimenko (1914a, and b) have, in fact, 

 already classified it thus under the name rhodoxanthin, which appears 

 to have been the name first applied to this pigment by Tswett (1910b). 

 The discovery of the same pigment in the pond-weed (Potamogeton 

 natans] by Monteverde and Lubimenko has been mentioned in an 

 earlier paragraph, and its characteristic properties given. 



Monteverde and Lubimcnko's study of the Thuja pigment differs 

 from Tswett's in that the pigment was isolated in nearly pure crystal- 

 line form, making it possible to show that Tswett's four banded spec- 

 trum for rhodoxanthin in carbon disulfide was probably due to some 

 admixed carotin or xanthophyll, the pure pigment showing only three 

 bands. According to Monteverde and Lubimenko many of the coni- 

 fers owe their winter reddening to rhodoxanthin. 



Lycopin, the red isomer of carotin, is also involved in winter red- 

 dening, according to Lubimenko (1914a). Two conifers whose cone 

 scales owe their winter color to this pigment are mentioned in Table 3. 

 The plants were studied under tropical conditions. 



Carotinoids in Flowers 



Yellow, orange and orange-red tints are especially abundant among 

 flowers. Marquart (1835) was the first to name the yellow flower pig- 

 ments, calling them anthoxanthins to distinguish them from the blue, 

 violet and red pigments which he called anthocyanins. Marquart 

 noticed that certain of the anthoxanthins gave a blue color with con. 



