LICHENOLOGY OF ICELAND 



201 



distance owing to their light greyish-green tone of colour. Their 

 character-plants were Drijas (F /o 100), Glnmiflorce (F /o 100) and 

 Empetnim (F /o 90), besides less important quantities of dwarf- 

 birches (F /o 10) and Silene acanlis (F /o 10). As indicated by the 

 names, the plant-covering is rather low; the soil was stable (not 

 drifting) and no abundantly leaf-shedding plants were predominant 

 in it. 



Such areas were peculiar by the vegetation being also phy- 

 siognomically highly dominated by lichens, especially crustaceous 

 lichens, for lichens, taken as a whole, were found in all the samples 

 (F /o 100). Fruticose lichens (F % 100), do not play any dominant 

 part physiognomically, in spite of their high frequency-percentage 

 (F /o 100), that is to say, they are not very conspicuous as masses. 

 This is in a way also true of the foliaceous lichens (F % 33), whilst 

 crustaceous lichens (F /o 100) are dominant to an unusual extent. 

 This is a very peculiar feature, as it must be remembered that 

 crustaceous lichens, taken as a whole, have very great difficulty in 

 holding their own amongst other competiting plants, for they are 

 very easily choked by being even very slightly covered over by 

 larger neighbours. Taken as a whole, the association just described 

 may be regarded as a characteristic Arctic association, poor in 

 phanerogams and rich in lichens. 



The following species occurred: 



