920 



mounlain planls generally have no limit of cxlension downwards 

 sliort of the sea-level, and that the subalpine region extends to 

 the coast. 



IV. THE PLANT-FORMATIONS. 



An altempl has been made in the preceding pages to describe 

 external factors which influcnce vegetation, to consider the biologicai 

 circumslances of most importance in enabling the piants to thrive 

 under these external conditions, and to survey the verlical distri- 

 bution of the species. Keeping these in view we now propose to 

 describe the plant-associations with regard to their development 

 and their dependance on each other. 



It may be stated as a general rule, that the more insular a 

 climate, and the more irregular the configuration of the surface, 

 then the more difficult it is to form in one's mind a definite 

 picture of the plant-associations, which under these conditions merge 

 gradually into each other, and are liable to frequent change. This 

 holds true in a marked degree for the Færoes. The great humidity 

 of the atmosphere, the frequent and abundant rainfall, and the re- 

 sulting moistness of the soil nearly everywhere, togelher ensure 

 almost constant and sufficient supplies of that most important fac- 

 tor, water. 



Consequently most of the plant-associations are closely related, 

 and the distinctions between them depend on small differences 

 in the quantity and the quality of water. It will easily be 

 understood, that distinctions so slightly defined are difficult to 

 maintain. 



The difficulty is further emphasised by the incessant changes, 

 up and down, which characterize the Færoese landscape, and which 

 within a single square meter may present to the planls widely 

 varying conditions as regards access of water, protection against 

 wind, light and shade, etc. The arrangement of the plant-associa- 

 tions which is attempted in the following pages is therefore some- 

 what more abstract than is the case in most other countries, and 

 it will be necessary again and again to indicate the gradual transi- 

 tion from one association to another. 



The following are the main groups used as a basis for our 

 classification (for complete scheme see »Contents«): 



