711 



begins at a depth of about 3 to 4 feet; the -S//c/{/os//>/jo/i-association 

 growing above that would theii be reckoned littoral. 



I have not, however, done this. A comparison between this 

 algal vegetation and that of a sheltered tidal locality e. g. Vest- 

 manhavn, proves that under the Fncaceæ-iormat'ion just below the 

 lowest water mark, a perfectly similar vegetation, the Stidyosiphon- 

 association, is found, whicli is here sublittoral. 



In this area of the sea the littoral region is therefore but slightly 

 developed, only consisting of some scattered Pelvetia, Porphyra um- 

 bilicalis, Fnciis vesicnlosns and a few others, besides some crusts of 

 bluish-green algæ, Hildenbrandia and Rhodochorlon. 



The algæ-vegetation found on exposed coasts differs as a rule 

 considerably from that found on sheltered coasts; as in the former 

 a great many species occur that are not always found in the latter 

 piaces, and as the species common to both piaces are often re- 

 presented by varying forms in each place I have divided the algæ- 

 vegetation into that of exposed and that of sheltered coasts. The 

 Norwegian investigators Hansteen and Boye have dealt in the 

 same way with the algal vegetation of the west coast of Norway. 

 We will first consider the vegetation of exposed coasts. 



a. Exposed Coasts. 



The Hildenbrandia-Formation, 



or the formation of the crustlike algæ as well as of lichens is widely 

 spread along the exposed coasts of the Færoes. It covers the rocks 

 with a dense mal of various colours to a considerably height, i. e. up to 

 more than two feet above the level of the sea and down to the Coral- 

 /z/?a-formation. The uppermost part of it mostly consists of lichens, 

 which, according to the Rev. Deichmann Branth, belong to dif- 

 ferent species of Verrucaria, but crusts of bluish-green algæ soon 

 appear, especially Calothrix scopiilorum, Riviilaria atra etc. and the 

 crimson Hildenbrandia rosea; the last mentioned algæ I have found 

 on the west coast of Vaago, about eight feet above the level of the 

 sea. At a shorter distance from the sea, Hildenbrandia becomes more 

 and more predominant, still crusts of lichens and bluish-green algæ 

 are intermingled with it, and another crust-alga, Ralfsia vernicosa, 

 can now be found; this however prefers littoral pools where the 

 water is constantly renewed by the surf. The walls of such basins 



