706 



onal level out of which they never thrive or only exceptionally. 

 We therefore find the same belt-like mode of growlh in the water- 

 pools on the beach and practically all round the coast, one algal 

 community gradually replacing another, exactly as an inland tlora 

 grows in belts round lakes and pools. 



Lastly, numbers of large and small pools and basins fdled with 

 water are found on the beach at every possible level above the sea, 

 sometimes so high up, that they are only filled with salt water by 

 the storms of winter and consequently get more or less brackish 

 and polluted in the course of summer, sometimes so low tliat they 

 are cut ofF from the sea only for a short time at low ebb; the great 

 variety of the algal vegetation in these shore-pools is naturally due 

 to these varying habitats. In fjords and sounds the bottom fre- 

 quently consists of stones or gravel forming a developing ground 

 for many algæ, but most often the bottom is soft, covered with 

 sand or mud which, apart from various free-floating algæ, is per- 

 fectty barren, as Characeæ are wanting, and Zostera, which at other 

 piaces generally covers such regions of somewhat shallow water 

 and often shelters a rich epiphytical algal vegetation, is but rarely 

 found in the Færoes; it has only been met with in the innermost 

 parts of Vaagfjord on Sydero, covering the bottom of a small lo- 

 cality where the water was from 1 to 2 fathoms deep. 



On the whole, however, the rocky coasts of the Færoes must 

 be considered especially favourable to algal vegetation; wherever 

 one approaches the coast, it is found covered by a luxuriant vege- 

 tation, and such barren rocks as on the coasts of Greenland, men- 

 tioned by Rosenvinge (71, p. 152), are nowhere found on the 

 coasts of the Færoes. 



As to the conditions at the bottom, these are not every where 

 favourable to the algæ. In the fjords, the bottom in shallow water 

 often consists of sand, and in deep water, as in the sounds, of mud. 

 Yet, large regions are covered with stones or rocks offering a fa- 

 vourable habitat for the growth of the algæ. On account of the 

 great depth sometimes met with in the immediate vicinity of the 

 land, the algal vegetation naturally disappears at such piaces close 

 to land, the depth-limit of the sublittoral region being soon reached 

 here. According to the most recent survey, the curve of 25 fathoms 

 is found at a mean distance of about 6000 feet from the coast in 

 southern islands, but only 2000 feet in the northern, especially in 

 the Sounds. Occasionallv it lies several miles from the coast. 



