The Botany of Iceland - 01.12.1912, Page 103

MARINE ALGAL VEGETATION
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close to this limit; 6 species (1 red, 3 brown, 2 green) have their
area of distribution in the ujiper and lower littoral zones, and to
a depth of 10 metres, these species are mentioned under the Upper
Littoral Zone, and there, 5 of them are reckoned as littoral. 35
species (10 red, 15 brown, 10 green) grow in the lower littoral
zone, and to a depth of about 10 metres. They appear to be about
as common in the lower littoral zone as in the belt between the
limit of low-tide and the depth mentioned. 18 species (12 red, 3
brown, 3 green) grow in the lower littoral zone, and to a depth
of more than 10 metres; these belong to the species which have a
lower downward range, 15 of them have their uppermost limit in
the lower littoral zone, and 3 of them in the upper littoral zone.
The species characteristic of the lower littoral zone are especially
the 19 species which are found there only, and the 35 species
which extend to a depth of about 10 metres, for some of these (e. g.
Rhodymenia and Halosaccion), by occurring in masses, often cha-
racterize large portions of the lower littoral zone.
2. The Belt down to a deptli of about 10 nietres. In
the table 103 species are recorded from this belt. Of these, two
occur also in the upper littoral zone, and have been previously
mentioned (Rhodochorton Rothii and Hildenbrandia), 6 occur also
in the upper and lower Iittoral zones and are mentioned above,
35 occur also in the lower littoral zone (see under this heading);
while 9 species are found only at this depth, but of these some
tnav be presumed to extend further downwards and some may
possibly occur in the lower littoral zone. 19 species extend down-
wards, witli their uppermost limit in the upper and lower littoral
zones, as, for example, Conchocetis rosea which occurs in the upper
littoral zone and is absent from the lower littoral zone, besides the
18 species mentioned under the Lower Littoral Zone. 32 species
with a downward range have their uppermost limit at a depth of
about 10 metres.
Besides the 9 species which are found only in this belt, it is
especially the 35 species which this belt has in common with the
lower littoral zone which characterize the belt, as some of them —
those mentioned under the Lower Littoral Zone — by occurring
in masses often characterize large portions of the bottom.
By comparison it can easily be seen that the lower littoral
zone is nnich more closely related to this belt than to the upper
littoral zone, which, amongst other things, is evident from the great