LICHENOLOGY OF ICELAND 197 
respectively. The numerical preponderance as regards Iceland is due 
to the foliaceous and especially the crustaceous lichens. 
The mass-occurrence (in weight) in both countries is unknown, 
as is also the frequency-number in both countries. For a first-hand 
and direct consideration the difference does not appear to be great 
in these two respects, but we ought not to remain standing at this 
point. 
e. Heaths. 
Under this name I include all such associations as are identified 
in the field by the fact that all, or at any rate almost all, the 
sample-areas contain chamæphytes, mainly dwarf-shrubs. A phanero- 
gamologist will hardly suffice with so short and summary a cha- 
racteristic, and it is his task to investigate partly which growth- 
forms the heath contains, and what percentage of each (chame- 
phytes, hemicryptophytes, etc.) and partly what frequency-degree 
each of these growth-forms has. A vegetation of which some of the 
sample-areas contain Empetrum only, others Calluna only, and others 
again a mixture of both is, according to the diagnosis used here, 
a heath as entirely as a vegetation which contains exclusively 
Calluna in all its sample-areas, because Calluna and Empetrum 
belong to the same growth-form. When I here mention as a kind 
of diagnosis, the characteristic that all or almost all the sample- 
areas must contain some or other chamephyte, this should not be 
regarded as an analysis of the phanerogamic growth-forms of the 
Iceland heath -- such will no doubt be given elsewhere in this 
work — but it is simply an easily recognizable feature whereby 
one can perhaps in the future recognize such Icelandic vegetations, 
of which the lichen-vegetation has been investigated by me and will 
be described more fully later on in this paper; in a similarly sum- 
mary manner phanerogamologists describe lichen-vegetations, moss- 
‘vegetations, etc. in associations which interest them for the sake of 
the phanerogams. It is in addition a diagnosis of quite similar 
character as the diagnosis that a wood is an association in which 
every sample-area contains a tree or parts of a tree — a diagnosis 
which does not involve anything whatever as to the entire biologi- 
cal aspect of the wood, when all its species are enumerated according 
to their growth-form. 
I must add, that in the investigation of the heath-associations, 
I took, in the majority of the localities, sample-areas of 2 square 
