OLAF GALL0E 



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 Undersogelser," 

 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." Ny lander 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 Unders0gelser, 1913) mentioned 

 the figures given by Ny lander 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 oil' in this respect, 

 having on the whole, only one species of tree, which bears lichens 

 somewhat abundantly, viz. the birch. 



