The Botany of Iceland - 01.12.1912, Page 159

MARINE ALGAL VEGETATION
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mediate forms, so are the various associations connected. If the
deep-water character of the association is taken as a starting point,
we notice that it changes gradually with decreasing depths on ex-
posed coasts, and tliat somewhere near the limit of low-tide it
assumes an entirely different characler, which is displayed in tlie
leathery, long-stemmed form with a narrow and slightlj'-divided
frond (f. stenophi]lla). On an exposed coast this variety might be
termed the shallow-water type or perhaps, rather, tlie surf-type, in
conforniity with the surf-form of Fucus inflatus. The surf-character
was very beautifully and typically developed in the Vestmannaeyjar;
here f. stenophytla grew very socially, forming a continuous belt,
the upper boundary of which occurred almost at the limit of low-
tide. When during low-tide the waves receded it was very inter-
esting to see how easily the leathery, narrow, slightlv-divided laminæ
moved with the waves, and everywhere, as far as the waves receded,
tlie rocky substratum between the StenophyZ/a-individuals was quite
reddish in colour from the encrusting Phymatolithon polymorphum.
The Laminaria plants were very firmly attaclied to the rock — a
fact evidently well known to the fishermen, as tliey fastened the
boat to a Laminaria while we went ashore. Tlie stipe is leathery
and pliable, and the plants cling closely to the substratum when
the waves recede.
I liave found /'. stenophylla in other places, although not in
such abundance, and not quite so typical. Here the same rule
applies as with regard to Fucus inflatus and Laminaria saccharina,
that the tendency to vary seems to depend on the greater or lesser
movement of the water; on coasts which are somewhat exposed, a
Laminaria digitata-association is rather frequently found at about
the limit of low-tide, with a character midway hetween the surf-
character and the deep-water character.
If we again take the deep-water character of the association as
a starting point, and move inwards towards the protected coasts,
we see that the character changes again, but in another direction.
The slipe becomes shorter and the frond much broader and slit
into fewer and broader lobes. Within the fjords, in W. and E. Ice-
land especially, the character is entirely different from the deep-
water character. Here occur forms with very broad fronds which
are either undivided or divided into two, or a few, very broad
lobes (f. cucullata). Generally the depth is about 4—20 metres, even
deeper occasionally. I have found associations with this character
The Botany of Iceland. I. 10