206 OLAF GALLGE 
similar to that in Reykjaheidi. The dominant phanerogamic vegeta- 
tion upon the knolls consisted of Empetrum, grass and Calluna, 
together with small quantities of dwarf-birch, Arctostaphylos uva 
ursi, Betula nana, Vaccinium uliginosum and Dryas. On the sides 
of the knolls were found lichens with a frequency degree 80, viz. 
Cladonia pityrea (fruticose lichen; sterile). 
— coccifera ( — 5 — ). 
— rangiferina ( — TT) 
Peltigera rufescens (foliaceous lichen; — ). 
Cetraria islandica ( — 5: — ) 
Pertusaria oculata  (crustaccous lichen; fertile). 
Psoroma hypnorum ( = With 
Lecidea assimilata ( — eve 
Bacidia flavovirescens ( ; sterile). 
Lecanora tartarea ( — NES UE) 
The depressions between the knolls were covered with grasses, 
mosses, Calluna, etc., but lichens were absent. 
In a locality a few miles from the heath just mentioned a very 
knolly heath occurred on a lava substratum, with the same phanero- 
gams as that just mentioned, and the lichens also almost exclusively 
covering the sides of the knolls; only about 15 F °/o lichens occur- 
ring upon the horizontal surface. The species were: — 
Alectoria ochroleuca (fruticose lichen; sterile). 
Cladonia pityrea ( — CN 
Peltigera venosa (foliaceous lichen; sterile). 
Pannaria brunnea (Crustaceous lichen; fertile). 
Psoroma hypnorum ( — EIN 
Lecidea helvola ( — REE: 
Lecanora tartarea ( — Ba) 
Bæomyces byssoides ( — ; sterile). 
Consequently, it is common to the Knolly heaths we have 
been considering here, to have a very uneven substratum with an 
essentially different vegetation upon the knolls and in the depres- 
sions between them. Lichens occur in a highly varying frequency- 
degree (40—80—100 F °/o) and almost exclusively on the sides of 
the knolls. 
Type III. Wet Mountain-heaths. 
Still another type of heath is found in Iceland on mountain 
heights, in places where the snow-covering lasts a long time. I in- 
vestigated more closely some such heaths, for instance on the moun- 
tains east of Eyjafjöröur on Vadlaheidi, on July 3rd, 1913. The snow 
