01. AF GAI.L0E 



ability: this, \vhich is simply a special lichen ological employment 

 of a geographical principle commonly employed in almost all other 

 possible circumstances. 



If we want to compare the abundance of species of a certain 

 limited area, for instance, that of Iceland with that of other areas 

 within the same climate-belt or in others we must naturally first 

 and foremost employ just this last method, that is, we must take 

 for comparison areas equal in size to Iceland. 



It is in the nature of the matter, that such investigations in- 

 volve considerable difficulties and, in fact, they have not yet been 

 made at all. But before they may happen to be made, we must 

 help ourselves with less valuable and easier methods, which can 

 give us hints with regard to the questions which we wish to have 

 solved, and which will presently be more fully discussed. 



If we wish to compare the abundance of species of the 

 various plant-associations with one another, several methods 

 can naturally be employed, but already here the absolute figure for 

 the species is very elucidatory. Thus, for instance, it is very in- 

 teresting to ascertain the difference between the number of species 

 in a grass-Held and in a heath in Iceland (see above). But here also 

 it is naturally still more valuable to determine the number of species 

 of a certain unit of area in one association, and compare it with 

 an equally large area of another association, for instance the number 

 of species, let us say in one square mile of heath, compared with 

 one square mile of forest, etc. 



But in the main, these statistical investigations are as yet tasks 

 for the future, much still remains to be done in this respect, 

 but what we already know for certain as regards Iceland will be 

 recorded here. 



Iceland has, according to the list given here, about 285 species; 

 a few more may probably be added to this number by latter in- 

 vestigations, but judging from what is known only few. 



Now does this figure represent many or few species in propor- 

 tion to the area of the island? 



Let us first compare it with some countries from the Arctic 

 regions: Greenland has 287 and Spitzbergen 207 species. In pro- 

 portion to its area, Spitzbergen the smallest of the three coun- 

 tries - - has consequently the greatest number of species ; then comes 

 Iceland and - - as the one poorest in species - - that immense Green- 

 land, which has, within its domain, an almost equally great absolute 



