740 



The algae which cover the walls farther in the cave are either 

 such littoral algae as would be* found in the open air on the beach 

 in cracks and clefls or otherwise sheltered from strong light, or 

 sublittoral algae which here approach the surface of the water as 

 the light grows fainter. Some of the latter may even be found 

 at such a height, that they are dry at low tide. Among these there 

 are several Floridew which are usually only found at a great depth 

 in the open sea. When rowing into such a cave, a condensed but 

 exact picture is obtained of the algae -vegetation that growls on a 

 vertical rock in the open air, moving from the top downwards. 

 Immediatel}^ at the entrance there are of course littoral algae, but 

 they soon disappear, as before mentioned, and so does the Alaria- 

 association. The Laminaria hyperborea is found a little fartlier in, 

 but it also soon disappears, and only Floridece are left. 



By closer observation of the algae-vegetation, we find that, as 

 mentioned above only a few specifically littoral algae grow here. The 

 alga which is most widely distributed and found at the greatest 

 height is Rhodochorton Rothii. Far stretching vegetations of it like 

 a dense, low, brow^iish-red felt cover the walls and ceilings of the 

 caves (cf. the /?/70f/oc/7or/o7j-association, page 718). Even in the mighty 

 caves on Troldhoved it is certainly this alga which gives the more 

 than 50 feet high rocky vaults their redish hue. At the entrance of 

 the caves and close to the level of the sea it grows on the rock 

 in small, firm lumps of the size of a pea. 



From about the highest water mark downward, a dense, almost 

 blackish covering of Plumaria elegans is often found in the caves. In 

 the Faeroes I have only met with this alga in these places. Toge- 

 ther with Plumaria, a dense covering of Delesseria alata, Ceramium 

 nibriim, Polysiphonia urceolata, and others, are also found. They 

 form a dark red, tangled vegetation which is often joined by 

 Cladophora nipestris closer to the entrance of the cave. In a 

 cave on the northern side of Kvalbofjord on Sydero, a low, red 

 covering of a small Phyllophora (8, p. 359) w^as found, some way into 

 the cave. A little above the lowest w^ater mark, the elegant little 

 Callithamnion scopuloriim is abundant, and Callithamnion arbuscula 

 ma}^ also sometimes be found in the caves. It partly changes its 

 appearance here, becoming less ramified and of a lighter reddish 

 colour. Whilst the Corallina is most often the subvegetation at the 

 entrance of the caves, it is replaced by the Phymatolithon poly- 

 morphiim farther into tlie cave. At the entrance of the caves, for 



