156 Plant Pigments [March, 



the same experimental conditions (in 10 days), lycopin absorbed 

 30 percent of the oxygen from the air; Carotin 0.25 percent. Ly- 

 copin does not give a crystalHne iodin addition product, but a dark 

 green amorphous product with indefinite iodin content. It reacts 

 with bromin with the evolution of hydrobromic acid, but differs 

 from Carotin in that it takes up far more bromin than corresponds 

 to the hydrobromic acid evolved ; the Compound f ormed is probably 

 C4oH44Br26. It is very evident from these differences that the two 

 isomers must vary considerably in structure. 



Xanthophyll. The existence of a second class of yellow pig- 

 ments in leaves was first mentioned by Stokes,^^ who supposed the 

 existence of two xanthophylls. Sorby^^ beheved that there were 

 three such Compounds. Borodin^^ divided the yellow pigments into 

 two classes : the Carotins, soluble in benzine and slightly soluble in 

 alcohol ; and the xanthophylls, slightly soluble in benzine but soluble 

 in alcohol. His observations were confirmed by Monteviede,^* 

 Tschirch,^^ Tswett,^^ and Schunck.^'^ Other writers thought that 

 Carotin was the only yellow pigment accompanying Chlorophyll.^^ 

 The question was partially settled by the Isolation and analysis of a 

 crystalline representative of the second class of Borodin, by Will- 

 stätter and Mieg.^^ The high yield of the two pigments, Carotin and 

 xanthophyll, makes it very improbable that there are any other Caro- 

 tinoids (this term includes both classes of pigments) accompany- 

 ing Chlorophyll in the land plants. Tswett,^" on the basis of a Chro- 

 matographie adsorption analysis (the pigments in organic solvents, 

 filtered through a column of calcium carbonate, inulin or sugar, 

 are adsorbed in different zones; each zone is considered a chemical 



21 Stokes : Proc. Royal Soc, 13, 144, 1864. 



22Sorby: Quart. Jour. Science, 8, 64, 1871 ; Proc. Royal Soc, 21, 442, 1873. 

 23 Borodin : Melanges biologiques tires Bull, de l'Acad. Imper. de St. Peters- 

 burg, II, 512, 1883. 



2* Monteviede : Acta Horti Petropolitani, 13, 148, 1893. 



25Tschirch: Ber. d. deutsch, bot. Gesellsch., 14, 176, 1896; 22, 414, 1904. 



26Tswett: Ibid., 24, 316, 384, 1906; 29, 630, 1911. 



27Schunck: Proc. Royal Soc, 63, 389, 1898; 65, 177, 1899; 72, 165, 1904. 



28 Immendorf , loc cit., p. 18. Molisch: Ber. d. deutsch, bot. Gesellsch., 14, 

 18, 1896. Tammes, Flora, 89, 205, 1900. 



29 Willstätter and Mieg : Ann. d. Chem., 355, i, 1907. 



soTswett: Die Chromophylle in der Pflanzen- und Tierwelt, 1910, p. 233 

 (Warsaw). 



