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In the Glycerine-preparations I have seen of Pleurocapsa amethystea from 

 Greenland, the colour had evidently faded, but most frequently it still was 

 faintly dirty-violaceous. The colour of the preparations made of Icelandic 

 algæ from dried specimens is as follows: The large undivided cells are 

 most frequently of an intense blue or bluish-violaceous colour, which 

 sometimes remains after the first divisions, but usually in the divided cells 

 it is substituted by an intense grass-green or almost emerald-green colour. 

 On account of the green colour, the outlines of the cell-colonies of the 

 Pleurocapsa are very distinct on the red Rhodochorton-filament. This 

 difference in colour between the Icelandic and Greenlandic plants does 

 not seem to justify the foundation of a new species, for, as well known, 

 the colour of the same species in the Gyanophyceæ varies considerably. 

 Particularly may be referred to a closely related species, the Pleurocapsa 

 fuliginosa Hauck, about which Hauck (Die Meeresalgen Deutschlands und 

 Oesterreichs 1885, p. 515) remarks, that the colour of the contents of the 

 cells is „gold- oder roth-bräunlich bis schmutzig violett." I therefore 

 choose to call our Icelandic plant Pleurocapsa amethystea K. Rosenv. var. 



(Auctore Johs. Schmidt.) 



This species has only been found in the litoral region. 



E. I cel. Vattarnes 



N. Icel. Grjötnes (G. 0.); Eyjafjöröur. 



NW. Icel., SW. Icel. and. S. Icel. common. 



Fam. Oscillatoriaceæ. 



Plectonema norvegicum Gomont, Bull, de la Soc. bot. de France, 

 tome XLVI, 1899. 



On rocks at high-water-mark in company with Prasiola stipitata. 



NW. Icel. Skâlholtsvik. 



Phormidium autumn ale (Ag.) Gomont, emend. Johs. Schmidt Danm. 

 blaagr. Alg. p. 348 and 410. 



This species occurred in running fresh water in the litoral region 

 near high-water-mark. 

 E. Icel. Vattarnes. 



Spirulina subsalsa Orsted, Beretning om en Excursion til Trindelen, 

 Kröyers Tidskrift, 3. Bd., p. 566, 1842. 



In the lower litoral zone amongst other algæ e. g. Ralfsia deusta, 

 Lithothamnion a. o. 



NW. Icel. Kolbeinsâ. 



S. Icel. Melvfk near Reykjanes (CO.). 



