The Botany of Iceland - 01.12.1928, Side 24

348
JOHS. BOYE PETEKSEN
On Heimaey (Vestmannaeyjar) (404), on some woodwork near
the shore, I found a layer of green algæ which proved to be made
up of Pseudendoclonium submarinum.
In the woods, of which I have visited those at Egilstaðir (22,23),
Hallormstaðir (6Ga), Háls (155, 156, 157, 158, 159), and Norðtunga
(335), the bark on the trunks and branches of the birches as a rule
proved quite naked and without visible algal vegetation, occasionally
with a few lichens. In the samples which I collected in places
where I found something that might resemble algæ, none were as
a rule found; sometimes I found an imperfectly developed lichen
thallus or some few algal cells impossible to determine.
In Denmark all woodwork as well as the bark of trees is as
a rule covered with a dense layer either of algæ or lichens, and I
have previously described in more detail (1915, p. 304 f.) where the
one and the other sort of these growths are to be found. However,
even i Denmark naked woodwork and naked tree trunks are found
in certain places, particularly in very exposed localities.
This will perhaps explain the scanty development of this algal
community in Iceland. As regards the prevailing winds in that
country we find the following statement in Den islandske Lods
(The Icelandic Pilot) for 1927, 5th ed. p. 27:
»As a rule the wind in Iceland blows with a moderate to strong
breeze and many storms occur, thus at Stykkisholmr storms average
50 days annually, and are most frequent in the winter when a storm
will occur on an average every fifth day, while in summer storms
occur abt. every tenth day .... Storms in Iceland present special
dangers because they often spring up with great suddenness. Thus
it is no uncommon occurrence that a storm reaches its full force
in less than an hour, but on the other liand the wind may drop
again with equal suddenness. The quick changes in the force of
the wind are not only due to the fact that the centres of the cy-
clones pass very close by Iceland, but many of the storms that
appear suddenly are local fjord winds which may in places be very
violent. As a rule they are then gusty and foehn-like in character,
that is to say, they are accompanied by a coinparatively liigh tem-
perature and only carry a slight degree of moisture . . . Altogether,
in the case of the storms, too, local conditions make their influence
felt along the coasts of lceland«.
It must furthermore be borne in mind that, since there are
practically no trees in the island, the wind will be able to sweep