The Botany of Iceland - 01.12.1945, Blaðsíða 62

STEINDÚR STEINDÓRSSON
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is relatively high. The geophytes are declining as compared with the
mýri. Grasses are of real importance in this formation. According
to the main character species the jaðar can be divided into a Juncus
balticus jaðar and a Calamagrostis jaðar. The most important associa-
tions are:
1. Juncus balticus—Deschampsia alpina-Ass. (Tab. VII. A-B, 1).
Here J. balticus and Desch. alpina dominate physiognomically, but
in addition Armeria vulg.aris, Agrostis alba, and Sagina procumbens
are very frequent. None of these species occurs in noticeable numbers
in the other jaðar associations. The association was met with here and
there in Arnardalur, whence the only analysis made is derived; it was
not noticed in other places. Here and in analysis VII, 7 the H percentage
attains its maximum in the jaðar.
2. Juncus balticus—Salix glauca-Ass. (Tab. VII. A-B, 2-5).
In addition to the two character species, Equisetum arvense domina-
tes in this association, but Calamagrostis neglecta, Equisetum variega-
tum, E. palustre, Pleurogyne rotata, Parnassia palustris, Carex rigida,
and Polygonum viviparum are also numerous in some few analyses
though none of them can be regarded as constant species. The associa-
tion is distributed on Brúaröræfi. Analyses 2 and 4 were taken in Arnar-
dalur, analysis 3 is from Þorlákslindir. In addition this association
forms a fairly broad, rather continuous belt in the lower part of Fagri-
dalur, between the mýri formation and the Salix heath. Fig. 4 shows
the position of the formations in the valley. Analysis 5 is from Síðu-
Fig. 4. Profile from the north side of Fagridalur.