The Botany of Iceland - 01.12.1912, Side 124

110
H. JÓNSSON
This belt behaves sirnilarlj' in the Færöes (Börgesen, 12, p.
744). Both Boye (10) and Hansteen (25) mention a Pelvetia-torma-
tion from western Norway without mentioning Fucus spiralis. In
Finmark Fucus spiratis has the same manner of growth as in Ice-
land (Foslie, 18, p. 66).
The Fucus-belt.
The four associations which belong to this belt are the most
extensive in the littoral zone and three of them are found everywhere
on rocky coasts. The breadth of the belt naturally is dependent on the
degree of the declivity of the coast in addition to the nature of the
substratum. This belt occurs everywhere along the coast, but it is not
luxuriant to the same degree everywhere. Its vegetation is so dense
that tlie bottom is entirely covered, or almost so, by the Fucus
plants which during low-tide partly lie prostrate upon the rocks
and partly hang on them; seen from a distance it appears as a
brown-coloured belt of varying width along the coast. Tliese asso-
ciations are usually found on a rocky substratum, but they may
also occur on a fairly firm gravelly bottom; the latter is especially
the case at the head of the fjords. In such places their vegetation
is poor and the species grow scattered, attached especially to small
stones which are somewhat firmly embedded in the gravelly bottom.
Fucus plants are also found scattered on wood-work, for instance,
on wooden piles. On the wliole the species of Fucus require a
stable substratum. The dominant species are tlie following: —
Fucus vesiculosus. Fucus inflatus.
Ascophyllum nodosum. F’ucus serratus.
The first three species are common and grow very luxuriantly
along the coast; Fucus serratus, on the other hand, was found only
in a few places in S. and SW. Iceland; in Hafnarfjörður it grew
very socially, while in the Vestmannaeyjar it had a more scattered
growth.
The individuals of these species form pure associations which
usually occur in regular succession: Fucus vesiculosus growing upper-
most, Ascophyllum in the middle and Fucus inflatus (and Fucus
serratus) lowest of all. This succession is distinctly observable in
places where the bottom is ílat and gently sloping. But where the
bottom is uneven — a talus of debris — the divisions between the
belts are less regular, but can, as a rule, be discerned. It does not,
however, follow that the associations always occur quite regularly;