KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. N:0 5. 183 



to Farlow. I conclude from these facts that A. plumula is not more commonly distributed 

 nor more abundant in the northern Atlantic than A. boreale in the Arctic Sea, and 

 that the latter can be at least almost as luxuriantly developed as the former. 



Habitat. The species is sublitoral in the arctic region of the Polar Sea, descen- 

 ding to the lower limit of this zone. It is generally sublitoral even in the Norwegian 

 Polar Sea, though it has been met with here also in the litoral zone. It is a common 

 element in the formation of Corallinaceaj, although being of little importance for the 

 characterization of this division of the vegetation. I have found it most abundant on 

 half-dead bottom, attached to Desmarestia aculeata that lay loose on the bottom. It 

 was also found once rather abundant among Pliyllophora interrupta. Though preferring 

 an exposed coast, it enters also into deep bays. Specimens are generally found scattered, 

 but in Actinia Bay I found the species in pretty great, in Musselbay even in very 

 great masses. On the north coast of Spitzbergen it occurs during all winter, retaining 

 even at this season its ordinary appearance and continuing its development, which does 

 not however become vigorous before the month of March. During the winter season 

 it is always sterile. It has been found with tetrasporangia at Nordlanden in July and 

 August, at Finmarken in August and September, at Spitzbergen in July and August, 

 in the eastern part of the Murman Sea in June, July, and September. I have not seen 

 specimens with sporocarps from the Polar Sea. 



Geogr. Distrib. It belongs to the Atlantic as well as the arctic region of the Polar 

 Sea. In the latter region it is widely distributed and it certainly has its maximum of 

 frequency there. Part of that Antithamnion which is reported from the American Arotic 

 Sea and Bafl&n Bay is possibly to be referred to the present species. If that should 

 be the case, the species is circumpolar. The northernmost place where it has been 

 found is Treurenberg Bay on the north coast of Spitzbergen, Lat. N. 79° 56'. 



Localities: The Norwegian Polar Sea: Nordlanden according to specimens in Kleen's 

 herbarium; Finmarken at Maas6 and Gjesvser pretty common, but scarce, at Oxfjord 

 and Talvik local and scarce. 



The Greenland Sea: On the west and north coasts of Spitzbergen commonly diffused, 

 but in general scanty; in Musselbay abundant. 



The Murman Sea: the coast of Russian Lapland; the west coast of Novaj^a 

 Zemlya and Waygats from Matotshin Shar to Jugor Shar, commonly distributed, but 

 scanty. 



The White Sea: rare. 



The Kara Sea: the eastern coast of Novaya Zemlya at Uddebay in rather great 

 number; in Actinia Bay pretty plentiful, but local. 



The Siberian Arctic Sea: Koljutshin Isle, Pitlekay and Tjapka, pretty common, 

 but scarce. 



Of the forms mentioned above, f. typica is known from the Greenland Sea, 

 the eastern Murman Sea, and the Siberian Arctic Sea; f. lapponica from the Greenland 

 Sea and the western Murman Sea; f. corallina from N. Gusinnoi Cape on the Avest coast 

 of Novaya Zemlya. The form observed in the Kara Sea, though most nearly allied to 

 the last-mentioned, is not identical with it, but intermediate between it and f. typica. 



