CAROTINOIDS IN THE PHANEROGAMS 33 



called "chlorophyll grim." Carl Kraus (1875) observed the same 

 facts when he found that benzene extracts a yellow color from alco- 

 holic leaf extracts made strongly alkaline with KOH. He called the 

 yellow pigment xanthin and regarded it as a decomposition product 

 of G. Kraus' xanthophyll. 



Possibly following the hint given by Stokes (1864b), Sorby (1873) 

 developed a separation method for the yellow and green constituents 

 of a number of tj^pes of plants using alcohol and carbon disulfide. 

 Sorby named five members of a "xanthophyll" group of yellow pig- 

 ments as well as two chlorophylls, but pure pigments could not have 

 been obtained in most cases, since the methods which he employed will 

 not give a true separation of the various carotinoids of the chloro- 

 plastids. Of the various pigments named by Sorby the "yellow 

 chlorophyll" is obviously a xanthophyll mixed with some chlorophyll, 

 and the "orange xanthophyll" is for the most part carotin. Sorby's 

 "xanthophyll" and "yellow xanthophyll" are the only true xantho- 

 phylls, the former being in all probability a mixture of what are now 

 called a and a' xanthophyll, while the "yellow xanthophyll" appar- 

 ently consisted almost wholly of our present (3 xanthophyll, which is 

 characterized, as Sorby found for it, by the development of a blue 

 color when its alcoholic solution is treated with HC1. 



Crystalline Carotinoids from Chloroplastids 



The second group of studies relating to the yellow pigment in the 

 chloroplastids deals with isolation of crystals of carotinoids, and ter- 

 minated with the isolation and analysis of one of the pigments and 

 the discovery of its identity with the carotin of carrots. The various 

 studies were, for the most part, independent of each other and accord- 

 ingly resulted in the proposal of several different names for the 

 chloroplastid chromolipoids. 



Fremy's (1865) observations regarding crystalline chromolipoids 

 have already been mentioned. He apparently regarded the crystals 

 as related to his phylloxanthin, as no special name was proposed by 

 him for the crystalline pigment. Hartsen (1873a), however, several 

 years later, observed golden-red crystals in the deposit from the spon- 

 taneous evaporation of an alcoholic extract from green leaves. He 

 called the pigment chrysophyll, a name previously applied by Sorby 

 (1871b) to a group of water-soluble pigments from autumn foliage, 

 and later (1875) described a method for purifying the crystals by 



