4 2<>r OLAF GALL0E 



similar to that in Reykjaheidi. The dominnnt phanerogamic vegeta- 

 tion upon the knolls consisted of Empelruni, grass and 

 together with small quantities of dwarf-birch, Arctost(i}>ln/los 

 nrsi, Betuln nana, Vaccininm nli</inosuni and Dri/as. On the sides 

 of the knolls were found lichens with a frequency degree 80, vix. 



Cladonia pityrea iruticose lichen: sterile- . 



coccifera ). 



rangiferina ( ; 



ivlligera rufescens (foliaceous lichen; 

 Cetraria islandica 

 Pertusaria oculata (crustaccous lichen; fertile. 

 Psoroma hypnorum ). 



Lecidea assimilata 



Bacidia flavovirescens ( ; sterile). 



Lecanora tartarea ( ; ). 



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 u lichens occur- 

 ring upon the horizontal surface. The species were: 



Alectoria ochroleuca (fruticose lichen; sterile). 



Cladonia pityrea ; ). 



Peltigera venosa (foliaceous lichen; sterile). 



Pannaria brunnea icrustaccous lichen ; fertile). 



Psoroma hypnorum ( ). 



Lecidea helvola ( ; ). 



Lecanora tartarea ( ; ). 



Baeomyces hyssoides ( ; 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 80100 F %) 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 Kyjufjordur on Vadlaheidi, on July 3rd, 1913. The snow 



