The Botany of Iceland - 01.12.1914, Side 155

PHYSICAL GEOGRAPHY
339
on the roofs and in some places AchiIIea ínillefoliurrr, in various
districts Rhodiola rosea has been planted on the walls, and in the
northermost districts Cochlearia officinalis often occurs in abundance
upon the houses, and in some places Saxifraga rivularis. At their
base the house-walls are green with Prasiola crispa-, various mosses
also grow upon the houses, especially Brgum argenteum1.
Heather moors are extensively developed in Iceland both in the
lowlands and valleys, on mountain-sides and on hills to a height of
about 400 metres; they are not recorded from higher levels. On moun-
tain-sides and on hill-slopes the heather moor is almost flat, on level
land it is usually knolly; it is best developed upon old lava-streams
and it often forms the ground vegetation of birch coppices. The
dominant species are Empetrnm nigrum, Vaccinium uliginosum, V.
mgrtillus, Arctostaphglus uva ursi and Calluna vulgaris; the last
species is fairlv common in many districts, but never oecurs so abun-
dantly as the others. Moreover, among the heather there is usually
an abundanee of Drgas octopetala, Juniperus communis, Betula nana,
Rubus saxatilis and Salix herbacea. In heathy tracts at higher levels
and also above these in scattered patches, are found Loiseleuria pro-
cumbens, Cassiope hgpnoides and Sibbaldia procumbens. On the penin-
sulas on either side of Eyjafjördur patches of Phgllodoce coerculea —
which is not recorded from more southerly habitats — are now and
then found. There is a great variation in the distribution of the
dilferent character-plants in tlie heather moor; sometimes they all
occur mixed with each other; sometimes each occurs separately in
large or small patclies, so that the different areas may be designated
Vaccinium heaths, Empetrum heaths, Calluna heaths, Arctostaphglus
heaths, etc. Between the heather, as ground vegetation, other plants
occur in abundance, especially immigrants from the knolly grass-
land — from which the knolly heather-land often appears to have
been derived — for instance, Juncus trifidus, Elgna Bellardi, Luzula
mnltiflora, L. spicata, Nardus stricia, Agrostis canina, A. alba and se-
veral other Gramineæ, also Salix lanata, S. glauca, S. phglicifolia,
Silene acaulis, Thgmus serpgllum, Bartschia alpina, Alchimilla alpina,
Thalictrum, Galium, Hieracium, and many others. In addition, there
is very often a moss-carpet of Grimmia hgpnoides beneath the heather.
Willow coppices. Although the various species of willows
are widely distributed they rarely form coppices proper, and willow
1 As regards the moss-vegetation on old house-walls see Helgi Jónsson’s
above-inentioned paper on the vegetation of South Iceland, 1905, p. 54.