The Botany of Iceland - 01.12.1942, Síða 47

THE PTERIDOPHYTA AND SPERMATOPHYTA OF ICELAND
45
occur higher plants, sometimes because of the strong current, and
sometimes evidently owing to the low temperature of the water. When,
on the more level stretches the rivers and brooks are more slow-flowing,
there may be a fairly copious vegetation of Cryptogams (Algæ, Mosses
and Equisetum), and also some few Phanerogams such as:
Eriophorum Scheuchzeri Callitriche spec.
Ranunculus hyperboreus Cerastium (Cerastoides)
b. The Vegetation of Lakes and Pools.
In shallow water, in the lakes and tams, there usually occur several
species of higher plants, such as:
Potamogeton gramineus
„ jiliformis
„ perfoliatus
„ natans
Sparganium affine
„ hyperboreum
„ minimum
Carex Lyngbyei
„ inflata
„ salina var.
Scirpus palustris
Limosella aquatica
Equisetum fluviatile
Callitriche hamulata
„ verna
Eriophorum angustifolium
Polygonum amphibium
Glyceria fluitans
Ranunculus trichophyllus var.
Alopecurus aequalis
Ranunculus hyperboreus
„ reptans
Subularia aquatica
Comarum palustre
Hippuris vulgaris
Myriophyllum alterniflorum
„ spicatum
Menyanthes trifoliata
Litorella uniflora
lsoetes echinosþora
The species-list of a particular lake is naturally to a great extent
dependent on the nature of the bottom (gravel, clay, mud, etc.), the
quality of the water, the depth, etc.
In pools, ponds and other smaller waters the vegetation may often
consist of but few species, occurring in such great abundance as to fill
up the basin. As a rule the number of species in the larger lakes is
small, and this is especially the case in the lakes situated at a higher
level; some of these lakes may even be almost destitute of phanerogamic
vegetation.
3. The Vegetation around Springs and
Solfataras.
a. The Vegetation around Cold Springs (dý vege-
tation). Cp. Helgi Jónsson, 1895 b, p. 73, Id. 1900, p. 25; Thorodd-
sen, 1914, p. 321; Molholm Hansen, 1930, p. 88; Steindórsson, 1936,
p. 450.