CHLOROPHYLL AND THE CHLOROPLASTS 345 



200-300 cc. of petroleum ether, it is filtered rapidly, and washed with a 

 mixture of 2 volumes of petroleum ether and 1 volume of alcohol. 

 The yield is about 0.25 gram. Carotin can, of course, be obtained very 

 much more easily and in larger yields from carrots than from green 

 leaves. Willstatter obtained 125 grams of pure carotin from 5000 kilo- 

 grams fresh or 472 kilograms dry carrots. 



Recently Schertz ^ has published detailed methods for the isolation and 

 purification of xanthophyll and carotin by methods based upon those of 

 Willstatter and Stoll. Schertz states that to obtain the purest prepara- 

 tions of xanthophyll, crystallization must first be made from methyl alco- 

 hol and that the pigment must then be precipitated from chloroform by 

 the addition of petroleum ether. 



The pigments of the algae difl:er in certain resi>ects from those of most 

 land plants, although there is little reason for believing that the course 

 of the photosynthetic reactions in the two types of plants is not the same. 

 The difference lies rather in the fact that while in most flowering plants 

 only four pigments are to be found, the algae present a variety of color, 

 red, brown and blue-green. These plants usually contain the same four 

 pigments, i.e., chlorophyll a and b, carotin and xanthophyll, although the 

 proportion of these is different, and in addition they contain other pig- 

 ments which give them their characteristic color and more or less mask 

 the color of the chlorophyll. A tremendous amount of work has been 

 done on the development of these pigments in the plants under different 

 circumstances, on the physiological role of the pigments as well as on 

 their chemical composition.** From the brown algae there has been iso- 

 lated a pigment which is typical of these plants, fucoxanthin, of the 

 empirical formula C40H54O6, and due to the efforts of Willstatter ^ and 

 his collaborators, the methods of obtaining this pigment, its properties 

 and chemical composition have been quite well established. The red pig- 

 ment, phycoerythrin and the blue pigment phycocyanin, though extensively 

 investigated, have as yet not been subjected to exhaustive chemical study. 

 They are complex nitrogenous substances, related to protein but of a 

 lower nitrogen content. There has been much speculation regarding the 

 possible role which these pigments play in the photosynthetic process, 

 though no satisfactory conclusions have been arrived at. Fucoxanthin 

 is a carotinoid and its absorption spectrum is similar to that of carotin 

 and of xanthophyll. Phycoerythrin and phycocyanin are strongly fluores- 

 cent, a property which has been the subject of much study. ^^ 



'Schertz, Jour. Agri. Res., 30, 469, 575 (1925). 



' Czapek, "Eiochemie der Pflanzen," 2nd Ed., I, 594. 



* Willstatter and Stoll, "Untersuchungen u. Chlorophyll," 141, 247 (1913). 



•"Lloyd, Science, 58, 91, 229 (1923) ; 59, 241 (1924) ; Trans. Roy. Soc. Canada 

 (3), 17, 129 (1923). Boresch, Biochcm. Zcit., 119, 167 (1921) ; Ber. bot. Ges., 39, 

 93 (1921). Hanson, Neiv Pliytologist, 8, 337 (1909). Kylin, Zeit. physiol. Chem., 

 69, 169 (1910); 74, 105 (1911); 76, 396 (1912); 82, 221 (1912); 94, 337 (1915). 

 Schutt, Ber. bot. Ges., 6, 36, 305 (1888). Wille, Ber. bot. Ges., 40, 188 (1922) 

 Teodoresco, Rev. Gen. Boi., 32, 145 (1920). 



