The Botany of Iceland - 01.12.1914, Blaðsíða 146

THORODDSEN
330
situation is suited to plant-life with southern exposure, an adequate
supply of water, shelter from sharp winds, and intense sunlight
during spring a “herb-slope” (Urteli1) or “herb-flat” (Urtemark) is
formed which on the one hand passes gradually into a rocky-flat
formation, and on the other into a birch coppice; it chiefly contains
the plants of these two formations, but the growth is dense and
luxuriant, so that the ground often appears to be entirely covered
by the closely-placed plants. Dicotyledonous flowering plants are
the most important, grasses are absent or of subordinate importance.
The soil consists of clay or gravel mixed with humus, upon which
mosses sometimes occur. Such herb-slopes are found in patches
on mountain-sides, on basalt-terraces or on the inclines below rocks,
in large ravines and in sheltered, sunny hollows; they often form
beautiful carpets, in which the various species usually occur inter-
mixed with each other. As a rule, the dominant species are Gera-
nium siluaticum, Spirœa ulmaria, Archangelica officinalis, Angelica
siluestris, Geum riuale, Bartschia alpina, Alchimilla uutgaris, Brunetla
uulgaris, Rnbus saxatilis, Vicia cracca, Myosotis aruensis, Leontodon
autumnatis, several species of Hieracium, Rnmex acetosa, Ranunculus
acer, Poa, Agrostis and Aira; intermixed with these occur several
other species, but less frequently. In some parts of the island other
characteristic species are frequently noted in “herb-slopes,” for in-
stance in East Iceland, Campanula rotundifolia and Saxifraga aizoi-
des, and in some places in South Iceland Valeriana officinatis and
Lgchnis flos cuculi.
Sand-covered tracts (sandar). As already mentioned, sandy
tracts occupy vast areas — several thousand kilometres surface —
in Iceland, both in the lowlands and on the plateau. The physical
conditions of these “sandar” differ somewhat, therefore their vege-
tation, although usually homogeneous and poor in species, may now
and then vary somewhat in details. The vast sandy wastes below
the glacier-bearing mountains (Jökulls) of South Iceland are mainly
l'ormed of glacio-fluvial gravel and sand, but also partly of volcanic
ashes and scoriæ, while there are wide stretches upon which both
the íine and the coarse gravel is mixed with clay. Sometimes exten-
sive stretches are occupied by alternating clayey flats and pebble-
covered river-beds; there are also tracts strewn with ice-striated
boulders, and extensive areas, especially on the plateau, covered
1 Urteli (herb-slope) and Græsli (grass-slope; see p. 335) denote plant-covered
slopes where dicotyledonous flowering plants and grasses are dominant respectively.