50 CAROTINOIDS AND KELATED PIGMENTS 



either chlorophyll or a closely related fore-runner of one of the chloro- 

 phyllins. Timiriazeff (1875) believed the absorption spectra of alco- 

 holic etiolated leaf extracts to be due to a small amount of chlorophyl- 

 lin admixed with Kraus' xanthophyll. Hansen (1884bi re.irarded the 

 bands in the red as due to chlorophyll. Montevenle 1 1894 1 regarded 

 the substance giving the bands in the red as a forerunner of one of 

 the chlorophyllins and called it protochlorophyll, a view which seems 

 to have been substantiated by the work of (Ireilach (1904). The 

 latter proposes to reserve the name etiolin for this green pigment with 

 properties like chlorophyll which exist- in etiolated leaves in very 

 small amounts, and to use the term in the same sense as Monteverde 

 used the word protochlorophyll. According to Greilach etiolin (proto- 

 chlorophyll I is not ;i constant constituent of the etiolated leaf but 

 appears and then di-appcars during the germination of the seed in 

 the dark. 



Arnaud (18891, following his earlier (1885) demonstration regard- 

 ing the identity of the yellow leaf pimnent isolated by him with the 

 carotin from carrots, minnled the yellow color of etiolated leaves MS 

 due to the s;iine piinni'nt. No ch< mical proof was offered of this but 

 he determined the quantity of carotin in the etiolated leaves of the 

 kidney bean I /%/*< />/x r///[/am I , using a colorimet ric method which 

 will be reviewed in a later chapter. Inasmuch as Arnaud's method 

 of analysis would preclude all but trace- of xanthophylls his result 

 may be regarded as the first proof of the presence of carotin in etio- 

 lated leave-. This \va> confirmed completely by Tmmendorff (1889) 

 the same year. He saponified the alcoholic extracts from etiolated 

 leaves, extracted the carotinoids from the soap with ether and obtained 

 crystals of carotin from the golden yellow extract. He did not suc- 

 ceed in obtaininu crystals from etiolated leaves which had developed 

 only a pale yellow color, hut only from those having a more orange 

 color, but this cannot be interpreted as indicating another pigment in 

 the less pigmented leaves, as Immendorff believed, but must be re- 

 garded as due solely to differences in concentration of pigment, as Kohl 

 (1902f ) has pointed out. 



Following Immendorff, Molisch (1896), Tammes (1900) and Kohl 

 (1902f) have independently substantiated the presence of carotinoids 

 in etiolated leaves from various plants using microscopic crystalliza- 

 tion methods on the fresh tissues. Inasmuch as our information re- 

 garding the yellow chromolipoids in the etiolated leaf depends at the 

 present time on the observations of these authors and the microchemi- 



