The Botany of Iceland - 01.12.1912, Síða 157

MARINE ALGAL VEGETATION
143
(f. pinnata). This alga is one of the largest found on tlie coasts of
Iceland, and may at times attain a length of 6—8 metres. The form
of the frond resembles to some extent the shallow-water form of
Laminaria saccharina, the thick mid-rib of Alaria corresponding with
the thickened median area of Laminaria. The fronds of both species
are thus well adapted to withstand the motion of the waves; in
fact both species are rather frequently found intermingled in a broad
belt along the coasts. On manv of the sunken skerries which are
such a danger in navigation, Alaria esculenta is the principal species,
indeed frequently growing alone. In Hvammsfjörður in SW. Iceland,
in places where a strong current exists (Röstin) there was found a
dense vegetation of broad-fronded Alaria esculenta /'. pinnata with
very long laminæ.
It is general knowledge that the lamina is torn in pieces by
the waves, and cases are frequent also in which the thin part of
the lamina is divided into many pieces by transverse slits, often
nothing remaining save the mid-rib itself, especially in the upper
part of the lamina. A luxuriant Alarietum was found below the
limit of low-tide at tlie extreme point between Seyðisfjörður and
Loðmundarfjörður; it consisted mainly of Alaria esculenta f.pinnata
with Ataria Pylaii and Lam. saccharina intermingled. It was at once
noticeable that the uppermost Alariœ were entirely frondless; the
stipes were completely overgrown with Ectocarpaceœ. It must be
admitted that tlie situation was exposed, and therefore it may well
be that the laminæ were destrojæd by tlie beat of the waves; but
there is just as much reason to believe that this was occasioned
by the drift-ice, which had made its appearance on the coasts some
time before my arrival. In this Iocality the Fucus-belt had also
been scraped off the rocks in several places which, in my opinion,
was caused by the drift-ice.
The Laminaria saccharina-association. This associa-
tion is verjr luxuriant, and occurs almost pure over stretches ex-
tending for miles along the coasts. It does not always grow on a
firm, rocky substratum: rather frequently it occurs on a pebbly
substratum, in which case the plants are attached either to a
single pebble or to several, as if lying at anclior. With dredgings,
therefore, it rather frequently happens also that the plants
with their “anchors” are dragged up from the sea-bottom. This
association is met with from a depth of about 2 metres, or from