The Botany of Iceland - 01.12.1912, Side 171

MARINE ALGAL VEGETATION
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B. The Sea-grass Vegetation.
The Zostera-association.
This association differs so much from the other marine com-
munities in Iceland — the marine algal communities — that it
must be regarded as not being in anj^ way connected with them.
The present community occurs especially on a substratum of muddv
clay, which the algæ avoid. The “roots” of the algæ — the liaptera —
are organs of attachment only, their sole function being, in most
cases, to attach the plant to the substratum — the stony substra-
tum —, while Zostera has true roots which obtain nourishment from
the substratum. For this reason Zostera requires a good nutrient
substratum which is generally soft. It is rare, indeed it must be
reckoned exceptional, for Zostera to be found growing on a hard
clay-substratum. I understand such cases to indicate that formerly
the substratum had been softer and then became more compact
owing to the deposition of clay and sand, and that the Zostera is
consequently about to disappear from such a spot. In places where
there is no danger of either sand or clav being deposited from
brooks or rivers the substratum will, nevertheless, scarcely remain
unchanged, as the mud and ooze which are thrown down every-
where in the ocean, when once they have been brought to a place,
readily accumulate and remain, in the shelter of the dense vegetation.
The Zos/ern-vegetation occurs widely distributed, especially in
SW. Iceland where, in many places, botli inside the smaller arms
of the fjords and in the large fjords such as Breiðifjörður, a sub-
stratum of muddy clay occurs between the coast and the skerries
which lie nearest. At Breiðifjörður, during low-tide, the pale-green
Zosfera-belt may be observed stretching for miles along the coast.
At Faxaflói also tlie Zos/era-vegetation has an extensive distribution.
Zostera is found, most certainly, on other parts of the coast of Ice-
land, but nowhere have I seen such extensive “meadows” of it as
in SW. Iceland.
The vegetation is generally pure and there is hardly an asso-
ciation of species in tlie sea off these coasts which is less mixed
than tlie Zostera-association. In other places Zostera is a fa-
vourite substratum for epiphytes, but however much I searched I
did not íind anything worth mentioning on the Zostera plants here;
in this respect the Zostera-meadow of Iceland agrees witli that of
the Færöes. At times, species belonging to the semi-littoral comtnu-