744 



this takes place generallj^ nearer the niontlis of the fjords, where 

 the sea-water inundates its hahitat at high tide. 



As mentioned ah*eady Pelvetia grows uppermost. On a sheUered 

 coast and at or a Httle above tlie highest water mark, it constitutes 

 an association which may spread far horizontally, but which is 

 vertically most often only one foot broad (see plate XXII). When 

 moist, it is of a light yellowish, olive -brown hue, but in calm 

 weatlier it is often liable to be dried; Pelvetia may be found quite 

 dry and stiff, and is then of a blackish hue. In tideless bays, it is 

 of course very liable to be drained, and circumstances are on the 

 whole less favourable to it here than in places which are subject 

 to a regular tide. This is quite clear from its slighter development; 

 specimens from the Kalbaktjord for instance, especially those growing 

 highest, were often but one inch long and consisted almost entirely 

 of receptacles, a form which has been called f. minima by Simmons. 

 Yet this dwarfish growth here in the fjords, may perhaps be partly 

 due to the great amount of fresh water which flows constantly 

 from the rivers, and which makes the surface-water with which Pel- 

 vetia comes in contact, very fresh. On coasts subject to the tide, 

 a mucli more vigorous and better developed Pe//;e/z«-association is 

 found. Other algae are but rarely found in the Pe/z;dza-association 

 as Simmons (p. 251) has pointed out, probably because only a few 

 algae are able to grow so far above the level of the sea in sheltered 

 places. Ulothrix flacca and Ectocarpus litoralis are however some- 

 times found epiphytically on Pelvetia, on the rock we find a sub- 

 vegetation of Verrucaria and Hildenbrandia rosea, and in cracks in 

 the rock, Rhodochorton Rothii and Ectocarpus litoralis. 



Below this association, a Fiiciis vesiciilosiis-Ascophylliim nodosiim- 

 association grows on a sheltered coast. It is very common and on 

 slightly sloping rocks it is widely distributed horizontally ; a specially 

 luxuriant growth of these algae seems to be found on coasts with 

 boulders and fragments of rocks of different sizes. On these stones, 

 Piiciis vesicidosus generally grows uppermost, in large dense clumps 

 and facing landward; below, Ascophylliim hangs down the sides 

 of the stones (see plate XXIV). Yet Ascophylliim may also be found 

 growing above Fiiciis vesicidosus. This I have seen in the Vestman- 

 havnbugt, for instance. Strom felt likewise writes (80, p. 10), that 

 Ascophylliim grows uppermost, and Fucus vesiculosiis farther down^, 

 whilst Rosenvinge reports thai Fucus vesiculosiis grows uppermost 



^ According to Jonssoii's observations (41, p. 192 — 193), it is usually the reverse. 



