701 



brown algae generally disappear at a depth of about 15 — 20 fa- 

 thoms, leaving an almost pure vegetation of Florklece , with the 

 exception of some green, and bluish-green algae, living in testa, 

 and, however, often turning reddish here. On the beach, especially 

 in its lower part, as well as in the upper part of the sublittoral 

 region, where light is still intense, a vigorous vegetation of brown 

 algae is found. To these must be added several algae, especially 

 some green and bluish-green at the upper part of the beach, and 

 at the lower part several red algae. 



That this distribution is principally, perhaps solely due to 

 light, its quantity as well as its quality, may easily be proved by 

 an investigation of the algae -vegetation of one of the numerous 

 caves on the coasts of the Faeroes. When rowing into such a 

 cave, it will be observed, that the species of algae, common at 

 the entrance, gradually disappear and are replaced by a great many 

 different sublittoral Floridece, directly under the surface of the 

 Waaler ^. This will be more thoroughly explained later on, when 

 the cave vegetation is dealt with. This fact has also been men- 

 tioned by several investigators, e. g. Berth old and Falkenberg 

 (18, p. 220). But whilst Berthold only seeks the cause of the 

 distribution of algae in the intensity of light, Gaidukow^ main- 

 tains that it is entirely due to its quality. Founding his opinion 

 on Engelmann's well know^n investigations as w^ell as on his own, 

 Gaidukow^ has recently in an interesting and instructive paper 

 (35) clearly shown, that the distribution of the algae is not so much 

 due to the intensity as to the colour of the light. The fact is, 

 that the green and bluish-green algae grow uppermost, as the red 



^ 111 this connection it should however not be forgotten, that it seems as 

 if some sublittoral species on the shores of the Faeroes are only to be found at a 

 certain depth, never directlj^ under the surface of the sea, not even in dark places, 

 e. g. several species of Lithothamnion, Callophyllis laciniata, Rhodophyllis dichotoma, 

 Antithamnion Plumula, Desmarestia aciileata and D. viridis, etc. As to Greenland, 

 some species are likewise mentioned by Rosenvinge (71, p. 228) as never occurring 

 near the surface of the sea. He thinks that this is due to the fact, that temperature 

 and salinity both become less variable as the depth increases. Several of these algse 

 may however be found littorally in other districts. Kjellman for instance states, 

 that Desmarestia aciileata and D. viridis can occur in the littoral region, on the 

 west coast of Norway, and Antithamnion boreale is sometimes met with littorally 

 in the Norwegian Polar sea. Le Jolis (58) writes that Callophyllis lacinata is to 

 be found at the lowest part of the beach. As these algae do not appear on the 

 shores of the Faeroes at such a high level, even in the caves, it is most probably 

 due to the fact that they cannot bear the strong surf here. 



45* 



