The Botany of Iceland - 01.12.1914, Page 135

PHYSICAL GEOGRAPHY
319
On the strand sand, especially in South Iceland, there is a fairly
characteristic vegetation of Halianthus peploides, Cakile maritima,
Atriplex patnla, Stenhammaria maritima and Potentilla anserina;
often, each of these species occurs separately and in abundance, but
sometimes they are found intermixed in various ways. Cakile ma-
ritima usually occurs uearest to the sea, and Potentilla anserina at
the highest levels, occupying large areas, and occurring so abun-
dantly that the ground is quite interwoven by its creeping shoots.
On the slrand sand are also seen in small numbers Cochlearia offici-
nalis, Matricaria inodora, Silene maritima, Polygonum aviculare, Stel-
laria crassifolia, S.media, Capsella bursa pastoris, Glyccria distans,
Festuca rubra, Elymus arenarius, Carex incurva, etc. On the vast
sandy stretches along the south coast blown-sand formations are
frequent nearest to the sea; here Halianthus peploides and Elymus
arenarius occur in tutts; above this belt of sand dunes, tracts are
found occupied by a vegetation richer in species and consisting of
Potentilla anserina, Festuca rnbra var. arenaria, Thymus serpyllum,
Galium verum, Achillea millefolium, Juncus balticus, and several
others. But below the glacier-bearing mountains (Jökulls) the strand
sand quickly merges into glacier sand, which íbrms sandy wastes
extremelj' poor in plant-life.
At several places along the coast of Iceland salt-marshes are
found, overflowed by salt water, for example in Borgarfjördur, Myrar,
Hornafjördur and Lón. In Myrar the dominant species are Glyceria
maritima, Agrostis alba, Plantago maritima, Stellaria crassifolia, more-
over Heleocharis uniglumis, Triglochin maritima, Juncus bufonius,
several species of Carex, etc. H. Jónsson found that in some
places two-thirds of the area was occupied by Glyceria maritima and
one-third by Agrostis alba, each species occurred separatelv in patches;
some thick-leaved Plantago maritima occurred, however, in the Gly-
ceria patches1.
The Vegetation of the Fresh Water. Plant-life occurs very
S|)aringly in running water, and where strong currents are felt it
is usually ahsent. Nor do plants appear to thrive in glacier-rivers;
this is probably due to the low temperature of the water and the
current. In slowly tlowing river-arms on level land, in rivulets and
brooks there is often a considerable quantity of green algæ (Zygnema
and Spirogyra), both at the bottom and upon the surface; in South
Iceland Enteromorpha intestinalis is common in streams. The fol-
1 Bunadarrit, XX, 1906, pp. 150, 151.