KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 20. N:0 5. 57 



with on the west coast of Greenland, are cosmopolitan, if they are understood in that 

 extensive sense still usual with algologists, and on this account afFord us no clue for 

 deciding the question of their origin. One species, Antithamnion floccosum, whose form 

 in the Atlantic differs from the Pacific form, might possibly be regarded as having 

 issued from A. boreale ^), commonly dispersed in the Arctic Sea. Some species, Poly- 

 siphonia parasitica, P. nigrescens and Plocamium coccineum, that are also stated to occur 

 in the southern hemisphere, have possibly passed from the one sea into the other south 

 of America. The present disti^ibution of Callithamnion arbuscula is so limited that no 

 conclusion can be drawn from it as to the original native country of the alga; more- 

 over it appears in the Pacific in another form than in the Atlantic. Concerning the 

 few remaining species, I believe I must refrain at present from uttering any suppositions. 

 Thus it has been shown that the arctic marine Flora is rich in endemic species; 

 that several species which go far northwards in the Arctic Sea and are widely distri- 

 buted there, are only slightly spread south wards in the Atlantic; that there are a 

 number of species in the northern part of the Pacific which occur also in the Arctic 

 Sea, even in those parts of it which lie north of the Atlantic, but are wanting in 

 the Atlantic itself; and that of the species comparatively very numerous, which the 

 arctic Flora possesses in comraon with the northern Atlantic as well as with the northern 

 Pacific, a very large proportion consists of such species as are met with in the Arctic 

 Sea at high latitudes, amongst them several of the most characteristic forms of the 

 Arctic Sea. I think I am justified in drawing from these facts the conclusion that the 

 Flora of the arctic part of the Polar Sea is an old Flora and that it has developed 

 within the Arctic Sea. But this being so, it ought to be explained why several arctic 

 forms are met with at present south of the limits of the Arctic Sea, both in the Atlantic 

 and in the northern part of the Pacific. The occurrence of several arctic algaä on the 

 north-eastern coast of America is easily explained by their having been carried there 

 by the cold Labrador current, which moreover makes the external conditions on the 

 last-mentioned coast very similar to those in which the algaj live in the Arctic Sea. 

 But along the European coast of the Atlantic no current runs down from the Arctic 

 Sea; on the contrary, a current flows upwards into the Arctic Sea from the Atlantic. 

 Even if the occurrence of several arctic algas on this coast might be explained by their 

 having wandered southwards along the coast, from the Spitzbergen Sea and the Mur- 

 man Sea along the land of the Cisuralian Samoyedes a. s. o., this explanation cannot 

 be applied to the species met with at Iceland, and on the coasts of Great Britain and 

 France. The currents between the northern Pacific and the Arctic Sea are favourable 

 for carrying algaB into the Arctic Sea, but not for transporting them from the Arctic 

 Sea into the Pacific. However, the causes of the present distribution of the algse 

 in the great divisions of the Ocean need not nor ought to be sought for in the 

 conditions now existing on the earth, any more than the causes of the distribution 

 of the land-plants. Just as the phanerogamous Flora of Scandinavia contains se- 

 veral elements which are remnants from that period when the glacial formation 

 extended farther southAvards than in our days, those arctic algas occurring in the 



^) Compnre this species in the special part. 



K. Vet. Atalii. TInndl. Tlnnd. 20. N:o 5. O 



