ASSIMILATION OF CARBON 



21 



Lycopin 1 is closely related to carotin and has the same percentage formula 

 (C4oH 56 ); it is found in the fruit of the tomato (Solatium lycopersicum). Three 

 dark bands occur in the right half of its absorption spectrum (Fig. 10). 



Red alga? contain phycoerythrin, a protein-like substance, which is readily 

 soluble in water but insoluble in alcohol, ether, and carbon bisulphide. The 

 dark, bluish-red solution shows an orange-yellow fluorescence. It crystallizes 

 from salt solutions in hexagonal red crystals. ; 



Phycocyanin, 2 the blue pigment of the blue-green algae, Cyanophyceae, is 

 likewise of protein nature; it is soluble in water and glycerine but insoluble in 

 ether and alcohol, its crystals are indigo blue in color. 



The brown algae contain a pigment, phycophcein, 3 which is easily soluble in 

 water; in concentrated solutions it is dark reddish-brown. k 



Fig. 11. — Absorption spectra of carotin (above) and xanthophyll (below). (After Will- 

 statter and Stoll.) The Fraunhofer lines and the wave-lengths (in pp) are shown on the upper 

 line of each diagram. 



Engelmann 4 studied the absorption spectra of bright-colored leaves of vari- 

 ous plants, and Stahl 5 investigated the biological importance of their coloring.' 



1 Montanari, Carlo, Materia colorante rossa del pomodoro. Le Stazioni Sperimentali Agrarie Italiane 

 37: 909-919. 1904. [Willstatter, Richard, and Escher, Heinr. H., Ueber den Farbstoff der Tomate. 

 Zeitsch. physiol. Chem. 64: 47-61. 1910.] 



2 Molisch, Hans, Das Phycocyan, ein krystallisirbarer Eiweisskorper. Bot. Zeitg. 53: 131-135. 1895. 



3 Schiirt, Franz, Ueber das Phycophsein. Ber. Deutsch. Bot. Ges. 5 : 259-274. 1887. 



4 Englemann, Th. W., Die Farben bunter Laubblatter und ihre Bedeutung fur die Zerlegung der 

 Kohlensaure im Lichte. Bot. Zeitg. 45 : 393-398, 409-419, 425-436, 441-450, 457-469. 1887. 



5 Stahl, E., Ueber bunte Laubblatter. Ein Beitrag zur Pflanzenbiologie. II. Ann. Jard. Bot. Buitenzorg 

 13: 137-216. 1896. 



' On phycoerythrin, see Haas and Hill, 1921. [See note 3, p. 6.] The best study of this 

 pigment is that of Hanson. (Hanson, E. K., Observations on phycoerythrin, the red pigment 

 of deep-water algas. New phytol. 8: 337-344. 1909.) — Ed. 



k But it seems to have been shown that there is no such pigment as phycophaein in the living 

 cells, this being a post-mortem product of the decomposition of a colorless chromogen. The 

 brown color of the brown algae is at least partly due to the presence of carotin. In this con- 

 nection see the following: Molisch, Hans, Das Phycoerythrin, seine Krystalisirbarkeit 

 und chemische Natur. Bot. Zeitg. 52: 177-189. 1894. Idem, Das Phycocyan ein Krystal- 

 lisirbarer Eiweisskorper. Ibid. 53: 131-135. 1895. Idem, Ueber den braunen Farbstoff 

 der Phaeophyceen und Diatomeen. Ibid. 63': 131-144. 1905. Tswett, M., Zur Kenntnis 

 der Phaeophyceenfarbstoffe. Ber. Deutsch. Bot. Ges. 24: 235-244. 1906. — Ed. 



1 The anthocyanins, or anthocyans, are other pigments that may be mentioned here. They 

 occur very commonly in flowers, leaves, stems, fruits, and even in roots, giving them a red, 



