('.[ROTIXOIDS IN Till' PHANEROGAMS 47 



decree Dl' colloidal atinre<:ai ion. \Yillstiitter and Mieg found lliat. 

 their crystalline xanthophyll readily entered into combination with 

 solvents I'orminu molecules of solvent of crystallization, which is 

 unquestionably a colloidal combination and might easily influence 

 greatly the adsorption properties of the pigments. The whole adsorp- 

 tion phenomenon deserves a further study using pure preparations of 

 the individual pigments. 



The xanthophylls arc usually regarded as pigments in which yellow 

 i- the predominating color. Red colored xanthophylls also exist, 

 however. Monteverde (1893) first called attention to a red pigment 

 in the reddish-brown leaves of the young floating pond weed (Potamo- 

 <n't<>n natans), an aquatic herb widely distributed in Russia, which 

 showed the xanthophyll properties in the Kraus separation. This pig- 

 ment has since 1 been called rhodoxanthin by Monteverde and Lubi- 

 menko (1913bl, who obtained it in crystalline form. The pigment 

 appears to be isomeric with the xanthophyll of the chloroplastids, as 

 lycopin is isomeric with carotin. It differs from the usual yellow 

 xanthophyll by dissolving in formic acid with a yellow color, yellow 

 xanthophyll dissolving in this solvent with a green color, according 

 to Monteverde and Lubimenko. Rhodoxanthin also shows spectro- 

 scopic absorption bands with characteristic position, especially in car- 

 bon bisulfide. A comparison of the xanthophyll and rhodoxanthin 

 band- in this solvent, as given by Willstiitter and Stoll (1913) and by 

 Monteverde and Lubimenko, respectively, is shown in the following: 



-\niitli<>i>lii/ll (W. and S.) Rhodoxanthin (M. and L.) 

 Band I 516-501 nn 575-553 HM- 



B.i nd II 483-467 " 535-515 " 



Band III 447-441 " 500-480 " 



The general solubility properties of rhodoxanthin appear to follow 

 thoM' of xanthophyll very closely. 



The relation between the empirical constitution of carotin and the 

 xanthophylls is such that the latter may be expressed very simply as 

 carotin dioxides. The character of the oxygen combination, however, 

 i- not dear, for according to the statement of Willstiitter and Micg 

 their cn>t;dline xanthophyll did not show the presence of cither 

 hydroxy, carboxyl or carbonyl groups. The xanthophylls, therefore, 

 cannot be nmple oxidation products of carotin. But these statements 

 iv-:i?-dinii the character of the oxygen in the xanthophyll molecule 

 p-ibly should be confirmed, for notwithstanding the fact that it has 

 not yet been found possible to t ran.- form carotin into xanthophyll in 



