52 CAROTINOIDS AND RELATED PIGMENTS 



the crystals to form, and that it frequently fails to show the presence 

 of carotin in plant tissues in which the pigment is known to be pres- 

 ent. By the use of suitable solvents van Wisselingh has demonstrated 

 very ingeniously, however, that it is possible to distinguish the xan- 

 thophyll crystals as a group from the carotin crystals in the mixture 

 formed by the Molisch method in various plant tissues. 



Returning now to the investigations regarding the chromolipoids in 

 various etiolated plant-, it may be stated that Molisch (1896) demon- 

 strated carotinoids by his alkali method in the etiolated leaves of 

 garden cress (Lcpidiuni *<itiruni i , barley (Hordeum vulgare) , hemp 

 (Cannabis satird), oats i/V.v///// \ f / ///// /// , and of balsam (Balsamina 

 hortensis, D.C.) and fir i.l/m.s <.rn/.sa), but not from the sunflower 

 (Heliantlmx annuux). in which only orange-red drops formed. Tammes 

 (1900J, using seeds from the same plants, save the balsam and fir, 

 substantiated Molisch's positive results with the alkali method, and 

 in addition obtained the carotinoid crystals in the etiolated di-cotyle- 

 dons of the suntlower. Kohl (19021) denounced most emphatically 

 the view of I'ringsheim that a specific pigment is present in etiolated 

 leaves, devoting an entire chapter of his monograph to this question. 

 In addition to the etiolated plants examined by Molisch and Tammes, 

 Kohl (19021) was able to form carotinoid crystals in the etiolated 

 leaves of the turnip i.S/m//y/.s <iH> ( i) and various varieties of Asphodel. 



It is apparent that we have as yet only indirect evidence that 

 xanthophylls are pre>ent in the etiolated leaf. ('. A. Schunck (1903) 

 has furnished direct evidence of xanthophylls in an isolated case, 

 namely, the etiolated leaves of the daffodil (Narcissus pseudo-nar- 

 cissus}, using the carbon disulfide separation method which has 

 already been described. A mixture of xanthophylls was found to be 

 present, but Schunck was unable to obtain crystals of chrysophyll 

 (carotin) although he had no difficulty in obtaining them abundantly 

 from alcoholic extracts of the etiolated leaves which had been allowed 

 to turn green in the sunlight. Greilach's (1904) spectroscopic obser- 

 vations of the pigments in etiolated leaves led him to conclude that 

 yellow pigments other than carotin are also concerned in the colora- 

 tion of the leaves. Ewart (1918) states that he has found 8 to 10 

 parts of carotin to one of xanthophyll in etiolated wheat seedlings. 



Several investigators have studied the question raised by the last 

 observation of Schunck, namely, what effect greening has on the con- 

 tent of carotinoids in the etiolated leaf. Wiesner (1877a) first studied 

 this point and concluded that the xanthophyll (carotinoids) diminished 



