LICHENOLOGY OF ICELAND 223 
water level as far upwards as the spray of the waves reaches. I have 
seen it developed very distinctly for instance on the sides of Seydis- 
fjérdur, Reydarfjérdur, Eyjafjérdur and in several other places. Its 
natural history is in all respects a repetition of what we know from 
Denmark, Finland, etc. Therefore, there is no special reason to 
dwell upon it more fully here. 
Foliaceous-lichen-associations are found here and there, 
fairly well-developed, especially in the low land, where they fre- 
quently consist of Parmelia saxatilis, P. lanata, P. stygia or of species 
of Gyrophora (G. cylindrica, arctica, erosa). Sometimes the one, 
sometimes the other species predominates, whereby several forma- 
tions may be distinguished (“‘Parmelia-formation,” “Gyrophora-forma- 
tion,’ etc.). As far as my observations go these communities are 
most luxuriantly developed in places where it is light and damp. 
For instance, they are found well-developed by the waterfalls at 
the head of Seydisfjérdur and by Dettifoss (North Iceland). 
The density of the plants is as a rule high and consequently 
the competition is keen, but regarding this point no detailed in- 
vestigations have been made. The crustaceous lichens are however 
mercilessly exterminated when Parmelia saxatilis puts in its ap- 
pearance; in many places this process of extermination may be 
observed in various stages. 
It is more rare for the Gyrophora spp. to dominate so de- 
cidedly; I did not see them as pure growths, as they may be found 
in Arctic countries. 
The Fruticose-lichen-association. Helgi Jénsson re- 
cords that Ramalina cuspidata often occurs abundantly on the rocks 
of South-west Iceland. He does not, however, state more explicitely 
whether it actually forms carpets. I myself never saw it occur in 
such abundance as to make it justifiable to speak of Ramalina- 
carpets, like those found on the shores of Bornholm. Nor did I 
come across such a feature on the coastal rocks of Iceland. 
Usnea melaxantha may sometimes be found in tolerable abun- 
dance near the snow-line on mountain heights, but I did not see 
this species either actually form carpets. 
Therefore it appears that Iceland has no continuous carpets of 
pendulous fruticose lichens which are attached to the rock- 
substratum itself like those we have in Denmark. 
Erect fruticose lichens (Alectoria, Stereocaulon, Cladonia, Cetraria 
aculeata, etc.) are frequently found covering the rock-substratum at 
