VI. THE ABUNDANCE OF LICHENS IN ICELAND. 



In my \vork "Forberedende Undersegelser til en almindelig Liken- 

 0kologi" (1818) 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 bv which to determine this numerically. 



\j / 



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 the}' give no information as regards the distribution 

 of the species in a vertical direction above sea-level in the "Region." 



Hut 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 Undersogelser til en almindelig Liken-0kologi" 

 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 



