KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND. 20. N:0 5. 61 
they show that sea-regions belonging to the area of the same sea-currents do not 
always possess an essentially similar vegetation, and that one must not accordingly, when 
attempting to divide the marine Flora into different geographical regions, fix the limits 
of these in all seas chiefly according to the sea-currents '). There may be found external 
conditions opposing insurmountable obstacles to the leveling tendencies of the currents 
and keeping regions isolated from each other, whose vegetations sea-currents are ever 
striving to level and to assimilate. The circumstances which counteract and annihilate 
the action of the Gulf Stream and which have therewith maintained the marine Flora 
of Spitzbergen at such a high degree of difference to that of the Norwegian Polar Sea, 
I consider to be chiefly the unsuitableness of the litoral zone of Spitzbergen for a richer 
vegetation, the low temperature of the water, and the insufficiency of the light. Most 
of the alge on the arctic coast of Norway belong to the litoral zone, and apparently 
it is chiefly alge of this kind that may be expected to be transported to Spitzbergen 
by the Gulf Sirehin and such objects as are carried by it towards the North. When 
they have arrived at Spitzbergen, they cannot thrive or spread there in their wonted 
places. The bottom is unfit for them, the ice destroys them, the temperature of the 
water is too low for them, and the layers of air with which they are brought in con- 
tact during ebb-tide, are often so cold as to injure the alge, stopping their development 
and diminishing their power of resistance. The temperature of the water in the sub- 
litoral region is at or below 0° during the whole year, accordingly very much lower 
than that to which on the coast of kway they are exposed in the coldest season. 
How could these Norwegian species, which love light and are accustomed to it, be 
expected to live here in darkness or dimness during a great part of the year, enjoying 
even during the rest of the year, on account of the different place where they grow, 
a less quantity of light than in those regions from where they have come? What has 
been said here of the Flora of Spitzbergen, holds good essentially even of the Flora 
of the eastern Murman Sea. 
Thus the out-lines of the history of the arctic marine Flora, as based on the 
results of the preceding investigation, may be stated as follows. The Flora has had 
its centre of development in the Arctic Sea. Its area was more extensive during the 
glacial period than at present. It has been recruited in later times by more southern 
species. The immigration has been larger into certain parts of the Arctic Sea than 
into others; in the Norwegian Polar Sea it has been so large that the Flora has here 
lost its arctic character; in other parts it has, on the contrary, been much smaller 
than might be expected on account of the currents prevailing, which are highly favour- 
able for an immigration from more southern seas. 
') Cp. J. G. AGarpu, Spetsb. Alg. Progr. p. 1. 
