935 



rays heat up the black sand and the dark surface of the rocks 

 (particularly those with a southerly exposure) and bring about a 

 more rapid evaporation of the fresh water from land-springs which 

 might wash out the salts. 



2. Subalpine formations. 



The natural plant-formations of the Færoes which bear no di- 

 rect impress of maritime inlluence, may be classified in a general 

 way according to their vertical range. The mountain plateaux and 

 the summits carry their own vegetation, the alpine formations; the 

 lower zones, from sea-level up to 200 — 400 metres altitude, harbour 

 the reniainder, which we are justified in calling subalpine forma- 

 tions, if an attempt is made to compare the vegetation of the Færoes 

 with that of Scotland^, North-England^, Ireland^, and certain parts 

 of Scandinavia and Switzerland*. 



It is almost self-evident that no hard and fast line can be drawn 

 between the alpine and the subalpine formations. This is parti- 

 cularly the case on the Færoes, where transitions from one forma- 

 tion to another recur with almost tiresome frequency, and an ac- 

 curately defined survey is almost impossible. 



In considering the subalpine plant-formations, it will be most 

 natural to arrange them according to the amount of water con- 

 tained in the soil, commencing with the lakes and ending with the 

 dry Cliffs. 



The Færoes contain numerous small lakes (tårns) and pools, 

 a few somewhat larger lakes (Sorvaagsvatn, Toftevatn, Leinumvatn, 

 Sandsvatn) and a great number of watercourses generally of no 

 great size. The vegetation in the standing and running water is 

 meagre; it may be divided into the following plant-formations: 



a. The plankton formation, 



b. The freshwater lithophyte formation, 



c. The limnæ formation of the lakes, 



d. The limnæ formation of running water. 



1 Hardy 1905 and 1906; Lewis 1905; Robert Smith 1898 and 1900; W. G. 

 Smith 1902 a, 1902 b, 1904 and 1905. 



2 Moss 1904; W. G. Smith, Moss and Rankin 1903; Lewis 1904. 



3 Pethybridge and Praeger 1905; Praeger 1903, 1904. 

 * Stebler and Schroeter 1892. 



