308 Myxophycece 



The pigment of the cells is principally phycocyanin, which 

 partially hides the chlorophyll and gives many of these plants 

 their characteristic blue-green colour. In some species, however, 

 pigments of other colours are present, such as carotin, myxophycin 1 

 and polycystin 2 . In the great majority of the blue-green Algae the 

 pigment is lodged in the cytoplasm in the form of small granules, 

 each of which usually contains a mixture of chlorophyll and 

 phycocyanin. These granules may occupy a somewhat indefinite 

 extent of the cytoplasm or they may be restricted to certain 

 regions, and it is a vexed question whether or not this pigmented 

 part of the cytoplasm should be regarded as a true chromatophore. 



Stockmeyer 3 and Zacharias 4 have each stated that the 

 pigmented protoplasm cannot be considered as a true chromato- 

 phore. Massart 5 also considers that although the coloured layer 

 functions as a plastid, it cannot be regarded as a true chromato- 

 phore on account of its indefinite limits towards the interior of the 

 cell, and the fact that it may contain both gas and liquid vacuoles. 

 On the other hand, Deiniga 6 finds in certain blue-green Algae 

 (such as Aphanizomenon and Nostoc) structures which he regards 

 as true chromatophores, having the form of a more or less 

 reticulated or perforated plate in contact with the cell-wall. 

 Zukal 7 also considers that Tolypothrix possesses a true chromato- 

 phore, and Fischer 8 and Hegler 9 each regard the pigmented 

 peripheral layer of protoplasm as a parietal chromatophore. The 

 latter carefully described the granular disposition of the pigment 

 and termed the pigmented layer a cyanoplast. Hieronymus 10 

 concludes that the pigmented peripheral layer is of the same 

 nature as the chromatophore of higher plants, but not identical 

 with it; and Wager 11 also states that its structure recalls the 

 chromatophore of other organisms. In the family Glaucocystacese 

 there is a true chromatophore. 



1 Chodat in Journ. Bot. de Morot, 1896, x. Myxophycin is identical with Sorby's 

 " pink phycocyanin." 



2 Zopf in Berichte Deutsch. Bot. Ges. 1901, xviii. 



3 Stockmeyer in Berichte Deutsch. Bot. Ges. 1894, xii. 



4 Zacharias in Bot. Zeitung, 1891, xlix ; in Abhandl. a.d. Geb. Naturw. Ver. 

 Hamburg, 1900, xvi. 



5 Massart in Recueil de 1'Inst. Bot. Univ. de Bruxelles, 19G2, v. 



6 Deiniga in Bull. Soc. Imp. Nat. Moscou, 1891, no. 2. 



7 Zukal in Berichte Deutsch. Bot. Ges. 1892, x. 



8 Fischer, Unters. iiber d. Bau d. Cyanophyceen u. Bakterien, Jena, 1897. 



9 Hegler in Pringsheim's Jahrb. fur wissensch. Bot. 1901, xxxvi. 



10 Hieronymus in Beitrage zur Biol. d. Pflanzen (Cohn), 1892, v. 



11 Wager, Report Brit. Assoc. 1901 (1902), p. 830. 



