The Botany of Iceland - 01.12.1912, Side 39

II. LIFE-CONDITIONS OF THE MARINE ALGAL
VEGETATION.
1. THE NATURE OF THE COAST.
he coast of Iceland consists partly of rock and partly of sand.
A The rocky coasts are rich in algal vegetation, while the sandy
coast is most frequently a “desert.” Here and there vegetation may
be found, however, on the sandy coast, where this is not exposed
to violent movement during any length of time. The vegetation then
consists of short-lived species.
The Rocky Coast. This abounds in indentations of various
size: inlets, fjords and bays. The size of the fjords varies greatly;
for example, the largest, Faxaflói, is ten geographical miles long
and twelve geographical miles broad, and Breiðifjörður is eighteen
geographical miles long and ten geographical miles broad. The
smaller fjords, on the other hand, are short and narrow indenta-
tions. Thus, owing to the indentations on the coast, the exposure
is apt to vary greatly. The extreme points and the outer portions
of the fjords have, as a rule, an exposed position, while in the
interior of the fjord the water is generally calm.
The rocks on the coast consist of basalt; in some places, how-
ever, tuff-coasts exist, and especially on the south coast. The fjord-
coasts of Iceland, which comprise South-west, North-west, North
and East Iceland, are mainly composed of basalt. The basalt varies
considerably but, as far as I have seen, it has no significance as
regards the distribution of the species, and no difference is seen,
for example, in the vegetation on the dolerite and the ordinary
basalt coasts. What is of prime importance to the vegetation is
not the rock itself but the nature of its surface. The surface is, as
a rule, very uneven, being eroded by water, weather and wind, and
furrowed by numerous fissures. Its nature is, therefore, such that
the algæ can easily attach themselves to it.