LICHENOLOGY OF ICELAND 201 
distance owing to their light greyish-green tone of colour. Their 
character-plants were Dryas (F °/o 100), Glumifloræ (F °/o 100) and 
Empetrum (F °/o 90), besides less important quantities of dwarf- 
birches (F °/o 10) and Silene acaulis (F °/o 10). As indicated by the 
names, the plant-covering is rather low; the soil was stable (not 
drifting) and no abundantly leaf-shedding plants were predominant 
in it. 
Such areas were peculiar by the vegetation being — also phy- 
siognomically — highly dominated by lichens, especially crustaceous 
lichens, for lichens, taken as a whole, were found in all the samples 
(F °/o 100). Fruticose lichens (F °/o 100), do not play any dominant 
part physiognomically, in spite of their high frequency-percentage 
(F °/o 100), that is to say, they are not very conspicuous as masses. 
This is in a way also true of the foliaceous lichens (F °/o 33), whilst 
crustaceous lichens (F °/o 100) are dominant to an unusual extent. 
This is a very peculiar feature, as it must be remembered that 
crustaceous lichens, taken as a whole, have very great difficulty in 
holding their own amongst other competiting plants, for they are 
very easily choked by being even very slightly covered over by 
larger neighbours. Taken as a whole, the association just described 
may be regarded as a characteristic Arctic association, poor in 
phanerogams and rich in lichens. 
The following species occurred: — 
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GEMM ALIAMACULEATA:. 2.4... Self Cavaco ee +. 100 + 
Berkoria Ochrolenca.. ss Sora + 100 — 
ihanmolial vermicularis. 2...2..2...... + + 
Beben Standical..!..0 0. Je: ae see + 20 + 
SDIOUMARSACCALA reiche eee + 10 + 
Bepkostumslacerum.2. has enennen En > 
Belftseraglepidophora. ». .2.......2..2... + — 
Or tartarea‘. sne Los + 100 + 
Bacidia’ flavovirescens...)..:2. 22. oss os +- 
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