The Botany of Iceland - 01.12.1928, Side 27

THE AERIAL ALGÆ OF ICELAND
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in their whole character, and as a matter of fact the algal vegeta-
tion appearing here is very similar to that of the ground, especially
by the occurrence of Diatoms.
II. THE ALGAL VEGETATION OF THE GROUND.
While the »proto-pleurococcoid« association (cp. Brand 1924)
on prominent objects is slighlly developed in Iceland, it is quite
otherwise with the algal vegetation of the ground ilself. As previously
mentioned, the wind must be supposed to have a very marked effect
on prominent objects, whereas it will not as a rule be able to exert
its full force on the soil itself because this is protecled by all sorts
of inequalities in the ground and by its covering of plants which-,
thougli low, is as a rule continuous. The soil will furtherinore be
kept in a constant state of moisture owing to the frequent rainfall.
Hence a rich ílora of algæ, both Cyanophyceæ, Chlorophyceæ, and
Diatoms, will be able to develop here. The physical conditions, too,
will evidently favour an algal vegetation. The country is mountainous
with water trickling from the earth in many places; throughout the
summer the snow on the highest peaks is continually melting and
forming water that keeps the mountain slopes wet in many places.
These conditions create numerous good growing-places which cannot
find their equal in a flat country like Denmark. Furthermore, the
neighbourhood of the hot springs presents special life-conditions.
Hence a characteristic flora af aerial algæ is found there.
Investigations by Esmarch (1911 and 1914), Moore and
Karrer (1919), and Moore and Carter(1926) have shown that in
addition to the algæ on the surface others are fouud in the deeper
layers of the earth. At the present moment the investigations have
heen carried down to a depth of abt. 3 m. At Rothamsted Experi-
mental Station it vvas found that the number of subterranean indi-
viduals and species is almost as great at a depth of 4 inches as at
tlie earth’s surface, while at increasing depths the number of indi-
viduals as well as species diminishes (Jolin Russell 1923, p. 109).
The investigations on this ssubterranean Algal Flora« are as yet in
their flrst slage, and I cannot in this wórk give any information
about this community in Iceland, my collections heing made as
early as 1914. Consequently the following pages will refer exclu-
sively to the »Surface Community* (Fritsch 1922, p. 225).