LICHENOLOGY OF ICELAND 207 
had just disappeared from the greater part of the heath, but it was 
still lying in many small patches in the depressions. It was evident 
that both climate and soil here were distinctly wetter and colder 
than in those places where the heath-types discussed above, usually 
develop. 
The substratum was very knoliy moraine soil, with knolls 
reaching up to the knees, and with deep, narrow moss-grown de- 
pressions between the knolls. Lichens were abundantly present; 
they occurred chiefly on the sides and on the horizontal surface of 
the knolls. The latter phenomenon [ have only met with on this 
type of heath, and it is no doubt to be explained as a result of 
the fact that, owing to the difficult conditions of vegetation, well- 
developed phanerogams do not occur on the top-surfaces of the 
knolls, as they occurred on the heaths situated on lower levels on 
the mountains. 
The following phanerogams occurred on the knolls: — Dwarf- 
willow (F °/o 90), Cyperaceæ (F °/o 90), Polygonum viviparum (F °/o 90), 
Empetrum (F °/o 40), Silene acaulis (F °/o 70), Cassiope hypnoides (F °/o 
40), Salix lanata (F °/o 20), and lastly there occurred, also on the 
knolls, 100 F °/o of lichens (i. e. 90 F °/o of crustaceous lichens, 60 
F °/o of foliaceous lichens and 60 F °/o of fruticose lichens). 
In the depressions between the knolls there grew dwarf-willows 
(F °/o 100), Polygonum viviparum (F °/o 100), a small amount of Em- 
petrum and grasses (F °/o 40), a small amount of Cyperacee, large 
quantities of mosses (F °/o 100), but no lichens. 
The reason of this absence of lichens must undoubtedly be 
sought in the fact that the depressions keep very wet during the 
short period of summer in which the heath is free from snow: 
this creates unfavourable conditions for the lichens. 
The following lichens were found upon the knolls: — 
Stereocaulon paschale (fruticose lichen; sterile), 
Cladonia turgida ( 
— coccifera ( 
= pyxidata ( 
— fimbriata ( 
— rangiferina ( — HAE NS | 
( 
( 
( 
( 
( 
( 
an MON 
= NEN 
) 
Cetraria islandica foliaceous lichen; sterile). 
— hiascens — TA) 
Dermatocarpon hepaticum — ; fertile). 
Peltigera aphtosa — ; sterile). 
— rufescens - NE) 
== lepidophora 
Gy ON D); 
