9^ CAROTINOIDS AND RELATED PIGMENTS 



lipoids of any other class of algae. The fresh plants owe their olive- 

 brown tint to the high concentration of the special algae carotinoid, 

 fucoxanthin, the most recent member of the chromolipoid pigments 

 to be brought to a definite chemical conception. The dried plants owe 

 their brown color to the pigment phycophain, which forms in the plants 

 after death, as the result of oxidation of colorless chromogens in the 

 cells. The belief that phycophain is the characteristic coloring mat- 

 ter of the brown algae still finds expression in the text books, but this 

 is only true of the dried plants. 



The brown sea-weeds which have been examined for carotinoids are 

 given in Table 8. The table shows that the pigments of these plants 

 attracted the attention of the early workers. While the scope of 

 these first studies was naturally limited by the prevailing knowledge 

 of the plant chromolipoids, they unquestionably paved the way for 

 the discovery of the fucoxanthfn which characterizes the brown algae. 

 The fact that certain species, like the Fucoidiae and Laminaria, are 

 abundant and easily obtained no doubt accounts for their popularity 

 as sources of material for investigation. Of the various investigations 

 mentioned in the table those of Tswett (1906), Czapek (1911), Kylin 

 (1912) and Willstatter and Page (1914) are the most important. The 

 chief contributions of these, as well as the earlier investigators, to the 

 subject may be summarized as follows: 



Rosanoff (1867) appears to have first expressed the belief that the 

 Fucoidice contain a special pigment besides chlorophyll. 



Millardet (1869), working in Kraus' laboratory, submitted the abso- 

 lute alcohol extracts from several species of both the dried and fresh 

 plants to the benzene separation method which had just been worked 

 out by Kraus. The yellow pigment remaining in the alcohol layer 

 was regarded as differing from the xanthophyll of higher plants and 

 was called phycoxanthin, the name which Kraus and Millardet (1868) 

 had already given to the pigment prepared in the same manner from 

 green algae and diatoms. Millardet was also the discoverer of the 

 brown water-soluble pigment of the Phceophyceos, to which the name 

 phycophain was given. Reinke (1886) first expressed the belief that 

 phycophain is a post-mortem product. Molisch (1905) first offered 

 experimental proof of this fact which was later definitely proved by 

 Tswett (1906) and confirmed by Kylin (1912). 



Askenasy (1869) noticed that the yellow pigment discovered by 

 Millardet in the brown algae turns blue when its alcoholic solution is 

 treated with HC1, a reaction which appears to be specific for fuco- 



