The Botany of Iceland - 01.12.1912, Blaðsíða 175

MARINE ALGAL VEGETATION
161
The Polysiphonia arctica-association is of importance
as regards the appearance of the sublittoral vegetation in E. Iceland.
This association does not occur in S. Iceland, but a corresponding
one occurs, which is however far less luxuriant, composed of Poly-
siphonia urceolata.
The Laminaria færöensis-association is known to occur
only in E. Iceland. This association is probably more widely dis-
tributed along Iceland than is at present known; the species occurs
at anv rate in N. Iceland. But I think that this species will hardly
be found along the coast of S. Iceland owing to the fact that shel-
tered localities are wanting there.
The Pelvetia-Fucus-spiralis-belt is most commonly dis-
tributed in S. and SW. Iceland, and composes there the upper part
of the Fucaceœ-community. As this belt is absent from E. Iceland
there is a considerable difference in the appearance of the upper-
most part of the Fucaceœ-community in the coastal districts in
question. Fucus spiralis is, however, found in E. Iceland.
The Community of Corallina is also peculiar to S. and
SW. Iceland and absent from E. Iceland. This community, or the
Corallina-Gigartina belt, is very luxuriant and often of considerable
extent in S. Iceland (and SW. Iceland), owing to which the semi-
littoral vegetation in E. Iceland and in S. Iceland differs highly in
character.
The Fucus serratus-association is poorly represented in
S. Iceland, but it is luxuriant in a single locality in SW. Iceland.
As Fucus serratus is rare, and somewhat resembles in appearance
the large, broad-leaved forms of Fucus inflatus which are common
everywhere, it plays only an inconsiderable part as regards the
appearance of the Fucaceæ-community.
The Phymatolithon polymorphum-association is pe-
culiar to S. Iceland, but as other crustaceous, calcareous algæ occur
in E. Iceland in a similar manner though less luxuriantly, the ab-
sence of Phymatolithon polymorphum is of no essential importance
as regards the appearance of tlie crustaceous-alga-vegetation.
From what lias been stated above it is evident that the occur-
rence of the Pelvetia-Fucus-spiratis-belt and the Corallina-Gigartina-
belt in S. Iceland (and SW. Iceland) gives to llie littoral and semi-
litloral vegetation of the southern district a character ditl'erent from
that of E. Iceland.
The Botany of Iceland. I.
11