XV 



fairly sharply marked. From here the boundary line goes to the 

 north of Iceland between Iceland and Greenland and then turns 

 considerably southwards to the north Atlantic coast of America. It 

 is qiiite impossible for us to set the limit on the American coast, 

 but we suppose that a large border-area is to be found which pos- 

 sibly extends southwards to Cape Cod (cfr. Farlow). Regarding 

 Iceland and Norway the southern limit of the Arctic Algæ-flora will 

 nearly coincide with that of the Isotherm of 4^ C. for a year in 

 Mohn's hydrographical map (tab. XVI). 



The main points are: The Boreal flora of the Atlantic extends 

 far into the northern Polar Sea on the coast of Europe, whereas, 

 on the coast of America the Arctic flora extends far southwards 

 into the Atlantic, which also corresponds with the hydrographical 

 conditions. 



A. THE ARCTIC GROUP (cfr. above) 



Rhodophijceæ. 

 Callymenia sanguinea Schmitz. 

 Ceratocolax Hartzii K. Rosenv. 

 Turnerella Pennji (Harv.) Schmitz. 

 Delesseria Baerii (Post. et Riipr.) J. Ag. 

 D. Montagnei Kjellm. 

 Poh'siphonia arctica J. Ag. 

 Rhodochorton spetzbergense Kjellm. 

 Dilsea integra (Kjellm.) K. Rosenv. 

 Petrocelis polygyna (Kjellm.) Schmitz. 

 Cruoria arctica Schmitz. 

 Lithothamnion flavescens Kjellm. 

 L. foecundum Kjellm. 

 L. arcticum Kjellm. 



13 species. 



Phæophyceæ. 

 Ectocarpus pycnocarpus K. Rosenv. 

 Omphalophyllum ulvaceum K. Rosenv. 

 Kjellmania subcontinua K. Rosenv. 

 Coelocladia arctica K. Rosenv. 

 Dictyosiphon corymbosus Kjellm. 

 Myriocladia callitricha K. Rosenv. 

 Laminaria solidungula J. Ag. 

 L. Agardhii Kjellm. 

 L. cuneifolia J. Ag. 

 L. groenlandica K. Rosenv. 

 L. nigripes J. Ag. 

 Alaria oblonga Kjellm. 

 A. dolichorhachis Kjellm. 

 A. elliptica Kjellm. 



14 species. 



B. THE SUBARCTIC GROUP. 



Subdivision I. 



The species we refer to this subdivision are common in the 



Arctic Sea, rather common in the cold-boreal area of the Atlantic 



Ocean as far south as to the Færoes and Nordland ; some of them 



occur, but rarely, as far south as England. 



