The Botany of Iceland - 01.12.1912, Síða 155

MARINE ALGAL VEGETATION
141
character of the community in sheltered and in exposed places,
which is evident from the description of the association given be-
low. In sheltered places the calm-water character predomi-
nates; to this belong the Saccorrhiza dermatodea-association, the
Alaria Pijlaii-association, the Laminaria fœröensis-associalion and
the calm-water associations of L. saccharina and L. digitata. Of the
very much exposed associations, the only essential one to be re-
corded is the Stenophylla-associiúion (see under L. digitata). In ad-
dition, a difference is evident according to the depth, and the as-
sociations then occur either with a shallow-water character
or with a deep-water character (see below).
In its main features, this community occurs in a similar man-
ner on the coasts of adjacent countries. The communities of S. and
SW. Iceland greatly resemble those of the Færöes, as has been fre-
quently mentioned, and also those of western Norway (Boye, 10;
Hansteen, 25) and of Finmark (Foslie, 18).
The Saccorrhiza dermatodea-association. I have most
frequently found this species just below the limit of low-tide, where
it is of medium size, and grows scattered. In water-filled depres-
sions in the lowest part of the littoral zone which, although they
lie above the limit of low-tide, belong from a biological point of
view to the lower-Iying' area, the species is often very social and
forms pure associations. I have found it growing very socially at
a greater depth (22—28 metres) within Reyðarfjörður in E. Iceland
off Hólmanes or thereabouts; the specimens which occurred there
were of large size. When the various Ectocarpacea; which may occur
on old individuals are excepted, the plants are usuallv free from
epiphytes. The association develops best in somewhat sheltered places.
The Alaria Pylaii-association. Alaria Pylaii, as mentioned
below, often grows interspersed amongst Alaria esculenta f. pinnata,
Laminaria saccharina and others, in somewhat exposed places; but
its real habitat is in the interior of the fjords, where the water is
calm. Here occur the typical, large, broad-fronded individuals: tliey
are often social in growth and then form pure or almost pure as-
sociations; but they are most frequently distributed in patches, and
then alternate with Saccorrhizeta or social growths of Laminaria
nigripes v. atrofulva. In such places occur also the broad-fronded
calm-water forms of Laminaria saccharina and L. digitata. Alaria