The Botany of Iceland - 01.12.1945, Side 101

THE VEGETATION OF CENTRAL ICELAND
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ing than the shrub heath. Possibly, however, this difference between
these closely related formations in Iceland and Greenland is due to the
position of Greenland in higher latitudes and to its colder climate.
The relationship between the formations appears most distinctly from
the following list of the constants and accessories of both. I here use
constant in the same meaning as B ö c h e r, i. e. “the species occurring
in more than half of the individual investigations”. Eleven observa-
tions were made of the Icelandic formation, twenty of the Greenlandic.
Constants Jcel. Greenl. Accessories Icel. Greenl.
Salix glauca I 71 19 Elyna Bellardi 4 3
— herbacea II 12 Dryas octopetala 3 —
Festuca rubra II — Salix lanata 4 —
Polygonum viviparum 11 20 Parnassia palustris 4 —
Empetrum nigrum IO 20 Cassiope hypnoides 4 6
Equisetum arvense 10 — Bartschia alpina 3 10
Carex rigida 9 15 Pinguicula vulgaris 3 3
Thalictrum alpinum 9 — Poa alpina 4 —
Vaccinium uliginosum 8 20 Juncus trifidus 3 70
Equisetum variegatum 8 — Luzula spicata 3 4
Tofieldia palustris 8 5 Hieracium alpinum — 9
Armeria vulgaris 7 — Bryanthus coeruleus — 8
Euphrasia latifolia 7 — Silene acaulis — 8
Carex scirpoidea — 10 Cerastium alpinum — 5
Antennaria alpina — 5
Alchemilla alpina — 5
Sedum roseum — 5
Scirpus ccespitosus — 5
Diapensia lapponica — 5
Trisetum spicatum — 5
NB. The Salix which occurs in the Greenlandic formation is not the pure S. glauca,
but S. arctophila X S. glauca.
A comparison of these lists will show how closely related the two
communities are; thus all the Greenlandic constants have been found
in the Icelandic Salix—Empetrum-association except Carex scirpoidea,
but this species is not found in Iceland. There is a greater difference
in the occurrence of the accessories, but in this connection I call atten-
tion to B ö c h e r’s remark (1. c. p. 59) that “there are hardly two
patches of heath which are entirely alike, so great is the abundance of
sociations ... in a Greenland heath-slope”. Something similar applies
to the Icelandic heath formation. I might very well agree in grouping
the analyses given here under a greater number of associations than
1 The figures show in how many observations the species occur.
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