CAROTINOIDS IN THE PHANEROGAMS 81 



less regard it as a minor constituent of the pigments of this fruit. 

 The microchemical Molisch crystals which van Wisselingh (1915) 

 obtained from the orange fruits of Rosa rugosa Thumb. (Rugosa 

 Rose) dissolved readily in phenol-glycerine, which is indicative of 

 xanthophylls. The pigmentation of the various rose fruits thus ap- 

 pears to vary. 



Sorbvs aucuparia (European Mountain Ash). Immendorff (1889) 

 believed carotin to be the pigment of the fruit of this plant. Both 

 Tammes and Kohl obtained microchemical crystals by the alkali 

 method, and van Wisselingh (1915) by the acid method as well. The 

 latter investigator made a closer study of the crystals obtained and 

 found red and orange-red platelets insoluble in phenol-glycerine, and 

 orange and yellow-orange platelets and needles which dissolved readily 

 in this reagent. Both carotin and xanthophylls appear to be present, 

 and a Tswett chromatographic analysis of the mixed pigments would 

 probably give the characteristic chloroplastid display of carotinoids. 

 Citrus aiirantiiun (Orange). Tammes (1900) obtained positive 

 carotinoid color reactions on the skin plastids but failed to secure 

 crystals after a short (18 day) submission to the alkali microchemical 

 crystallization method. Kohl examined the pigment of the pericarp, 

 and found only spectroscopically inert pigment, although he thought 

 there might be traces of carotin (carotinoids) present. Schunck 

 (1903) studied the skin pigment of several varieties of oranges and 

 found considerable amounts of water-soluble (anthocyanin?) pig- 

 ments, especially in the red skin varieties (Blood orange, Seville 

 orange and Tangerines). He found, however, that the alcoholic ex- 

 tracts yielded crystals of chrysophyll (carotin) and showed spectro- 

 scopically the presence of acid derivatives of B. and Y. xanthophylls. 

 Tschirch (1904) also obtained proof of the presence of water-soluble 

 non-carotinoid pigments in the orange skin. His spectroscopic study 

 of the principal carotinoid pigment, secured by the capillary method, 

 did not give satisfactory results. Gill (1918) has obtained a carotin 

 (carotinoid) test with orange skin extracts, using the color reaction 

 mentioned above. A more exact study of the orange pigments, using 

 chromatographic and solubility methods, as well as the improved 

 microchemical methods, would seem desirable. 



Solanum dulcamara (Bittersweet). Thudichum (1869) classified 

 the pigment as lutein. Hartsen (1873) obtained red crystals identical 

 with those from Tamus communis and Asparagus berries. Schimper 

 (1885) observed red crystals in the fruit plastids, and Tammes (1900) 



