238 OLAF GALL®E 
country, have also many more lichens than has Denmark, viz. 1100 
—1400 species. 
On the whole it holds good, as a general rule, as has been 
stated and more fully proved in my "Forberedende Undersøgelser,” 
that the Arctic countries and Iceland are poorer in species, even 
considerably poorer, than are the temperate or the subtropical 
countries. The cause of this fact may be disputed, but the fact itself 
cannot be denied. 
And yet it has been denied! For instance when discussing 
verbally with men of science in my own department, I have heard 
the assertion advanced, that exactly the Arctic regions, in contra- 
diction to what I maintained, were comparatively rich in species! 
In this respect they have referred to the results arrived at by Ny- 
lander in his “Synopsis methodica lichenum.” Nylander there 
shows that the Arctic regions are comparatively rich in species! 
But it should be noted that he arrives at this conclusion by com- 
paring the number of phanerogams (!) with the number of lichen- 
species. 
I have previously (Forberedende Undersggelser, 1913) mentioned 
‚the figures given by Nylander and his comments on them. They 
are I presume correct — both the figures and the comments — only 
they do not at all affect the circumstance which I am endeavouring 
to elucidate, viz., the abundance of species in relation to area; 
and therefore they cannot at all be used as a corrective of my 
results. And yet, in verbal discussions, I have more than once come 
across this entirely erroneous view. 
I have shown that the Arctic regions — as also Iceland 
— is poor in lichen-species in proportion to their area, 
far poorer than the temperate regions. 
But there are many details in this connection which require 
to be more fully discussed, and for that reason we will regard the 
separate biological groups of lichens more closely: Bark, Epiphyllous, 
Earth and Rock-lichens, in order, if possible, to arrive at some ex- 
planation with regard to the cause of the phenomenon. 
Bark-lichens. We must a priori expect the bark-lichens to 
be greatest in number in places where there is the greatest abun- 
dance of substratum for them, i.e. many species of trees, and in 
great number of individuals. Iceland is badly off in this respect, 
having on the whole, only one species of tree, which bears lichens 
somewhat abundantly, viz. the birch. 
