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 chamsephytes, 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 (chamse- 

 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 grow T th-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 chamsephyte, 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 



