VI. THE ABUNDANCE OF LICHENS IN ICELAND: 
| my work "Forberedende Undersøgelser til en almindelig Liken- 
Økologi” (1813) I have made a preliminary attempt towards 
characterizing the various zones of the globe, as regards their 
abundance of lichens. I shall now mention in short the problems 
pertaining to this department, which require to be solved more 
particularly as regards Iceland. 
The abundance of lichens in a country may be characterized 
in various ways, but those that, as a rule, will interest us most, 
are (1) the abundance of species and (2) the abundance of individuals 
(mass-occurrence) in a country. 
Let us firstly regard the abundance of species of the various 
climate-belts and the method by which to determine this numerically. 
This task is very comprehensive and cannot in reality be worked 
out with the aid of the floristical works, which we have at our 
disposal at present, and this for various reasons. The principal of 
these are the following two: — (1) The floras comprise, as a rule, 
politically — not with regard to climatology — limited areas, and 
(2) as a rule they give no information as regards the distribution 
of the species in a vertical direction above sea-level in the “Region.” 
But let us suppose these wants supplied at some future time 
by laborious and protracted investigations in the field. We shall 
then by that time be able to give the abundance of species 
of the various climate-belts in absolute figures — so 
many in the whole of the Arctic, respectively temperate, sub-tropical 
and tropical belts. 
I have reason to assume — as I have more fully shown in my 
“Forberedende Undersøgelser til en almindelig Liken-Okologi’ — 
that the abundance of the various climate-belts given in such ab- 
solute figures will show that the Arctic-belt is poorest in the northern 
