The Botany of Iceland - 01.12.1912, Side 145

MARINE ALGAL VEGETATION
131
association are as follows: — Chorda Filum, C. tomentosa, Chordaria
flayelliformis and Didyosiphon foeniculaceus. Scytosiphon Lomentaria,
Castagnea virescens and Coilodesme bultigera are also most nearly
related to this association. Some of the species occur in such abun-
dance that they may be said to form an association; this applies
more particularly to Chorda Filum. A pronounced Chorda Filum-
association occurs in many places at a depth of almost 3—4 metres
(measured during low-water of spring-tide). The individuals are ex-
tremely long, about 6 metres and, to a great extent, float on the
surface at low-tide. The substratum is, as a rule, clayish with
pebbles here and there. This association is often almost pure, hut
scattered individuals of Laminaria saccharina are not rare, although
they play no essential róle in the vegetation. Chorda Filum also
grows above low-water mark in the lower littoral zone, but there
it does not really form associations, although it may grow luxuri-
antly in many places.
Chorda tomentosa is also social and grows more luxuriantly
below low-water mark than above it. It often occurs in abundance
as a component of the sublittoral vegetation.
Chordaria and Dictyosiphon foeniculaceus are species which grow
socially, and rather frequently a Chordarietum or a Dictyosiphonetum
is found, usually with a limited distribution both below low-water
mark and above it, especially in water-filled depressions in the
littoral zone. The remaining species which have been mentioned
are also of rather social growth in many places, both below and
above low-water ntark, especially in pools. Coilodesme, for example,
was ratlier frequent in tide-pools in E. Iceland, and sometimes at
a verv high level, but then the individuals were frequently inflated;
in SW. Iceland the species grew at and below low-water mark in
company with Chorda Filum and Saccorrhiza.
With the exception of the above-mentioned Chorda Filum-ásso-
ciation, this vegetation occurs usually in patches, distributed be-
tween other associations. Thus it is closely connected with the
Enteromorpha c/af/irafa-association at the boundary between the
upper and lower littoral zones, and with the Rhodymenia-association
and the Monostroma fuscum-association at a depth of about 4 metres,
as has been previously mentioned.
In the Færöes a similar vegetation occurs as a part of the
Stictyosiphon-associaúon (Börgesen, 12, pp. 762—763).
9*