The Botany of Iceland - 01.12.1930, Síða 124
114
H. M0LHOLM HANSEN
atilis. Of more or less importance are Polygonum viviparum, Cala-
magrostis neglecta, Equisetum arvense and E. variegatum, Cardamine
pratensis, Thalictrum alpinum, Luznla spicata, Festuca ovina, F. rubra,
and Saxifraga Hirculus.
The Carex rariflora Myri. Cf. íig. 22 and table 24 A, 5 9.
On still damper ground the knolls disappear and witli them a
number of species, so that the species now onlv number 11.2, while
the density of species is 4.7. The geophytes, comprising especially
Cyperaceæ, form the bulk of the vegetation. The G percentage is
70.5, the HH percentage 4.2, the Ch and H percentages 14.1 and 11.1
respectively. The species group speclrum. shows tlie peculiarity of
a rise in the A percentage from 56 to 66 caused by a great rise in
the A 2 and A 1 percentages; the A 3 percentage, on the other hand,
is still reduced. The dominant species are Carex rariflora and Erio-
phorum potgstachyum, also, in spots, Carex chordorrhiza and C. ro-
strata. Other frequently occurring plants are Polygonum viviparum.
Salix gtanca, and Cardamine pratensís.
The Eriophorum polystachyum Flói. Cf. Table 24 A, 10—13.
On the flói, the dampest soil clothed with plants, knolls are
likewise absent, the ground is swampy as in the lowland flói, and
not firm enough to walk on. The succession of changes in number
of species, density of species, biological spectrum and species group
spectrum in the mýri formations here reaches its climax, as was
also the case in the lowland ílói.
The sole dominant here is Eriophorum polystachyum, here and
there a few inýri plants occur such as Carex rariflora, C. chordor-
rhiza, C. rostrata, C. saxatilis, Pohggonum viviparum, Salix glauca,
and Catamagrostis neglecla.
The Geiri Vegetation. Cf. table 25 A, 1—6 and figs. 23—25.
On slopes with a southern, western, and northern exposure a
special vegetation, the snow patch or geiri vegetation, inay be met
with. Its peculiarities are conditioned by a deep and constant snow-
covering in the winter. The snow falls early on these areas, covers
them without intermission throughout the w'inter, and only melts
well on in the spring.
The snow patches occur in two different forms. Most frequently
the snowr lies in long narrow bands on the southern, western, and