The Botany of Iceland - 01.12.1930, Blaðsíða 116
106
H. M0LHOLM HANSEN
the more conspicuous species includes: Empetrum nigrum, Salix
herbacea, S. glauca, Betula nana, Vaccinium uliginosum, Dryas odo-
petala, Silene acaulis, and Armeria vulgaris. The species Cassiope
hypnoides and Loiseleuria procumbens occur more frequently than in
melar even though they are not as dominant as in the knolly mo.
Of hemicryptophytes and geophytes the following occur: Poly-
gonum viviparum, Juncus trifidus, Luzula spicata, Festuca ovina,
Viscaria alpina, Galium Normanni, Thalictrum alpinum, Elyna Bel-
lardi, Carex rigida, Festuca rubra, and Poa alpina. Of pteridophytes
Selaginella selaginoides, Equisetum arvense, and E. variegatnm are
met with.
Along the upper margin of the large snow patches there occurs
a narrow belt in which Betula nana is the physiognomic dominant.
This formation will be dealt with later, under the geiri vegetation.
The Knolly Mo. Cf. fig. 19 and table 23 A, 1—5.
This type of vegetation commonly occurs on flat sheltered slopes,
on the lower slopes of elevations and ridges with melar above, in
small hollows in the Betula nana mo, and on the borders of the
snow patches. The surface is always knolly, but the knolls are
neither very large nor very high. Judging by tlie position the snow-
covering is deeper than in the two preceding types, the melar and
the level mo, though less deep than in the snow patches. As re-
gards moisture, the knolly mo occupies an intermediate position
betwreen tlie level mo and the jaðar vegetation.
The change in number of species and in density is continued
from melar through the level mo to the knolly mo and here we
have the values 35 and 15 respectively for the number of species
and the density. Biologically the change is likevise continued: the
Ch percentage has decreased, while the G and H percentages have
increased. The E and A percentages have remained constant, while
there is still a decrease in the A 3 percentage. There is a rise in
thc E 3 percentage.
While in the Betula nana mo Ch were dominant and H were
the subordinate element, the reverse is the case in the knolly mo.
Here H are the dominant. The respective averages for Ch and H
in the two types of vegatation are 47 : 38 and 37 :47.
The predominant chamaephytes are Empetrum nigrum, Vacci-
nium, and Salix herbacea. In more scattered growth there occur
Salix glauca, Silene acanlis, Armeria vnlgaris, Dryas octopetala, Thy-