720 



almost continuous, light yellow belt of dried up threads of Bangia, 

 on rocks and stones above the average high water mark. 



According to what Mr. E. Norum kindly informs me, Bangia 

 is found in the neighbourhood of Haugesund on exposed coasts, 

 to a height of 6 feet above the Balamis- region, often covering 

 sloping rocks abundantly. Mr. Norum supposes, that its total 

 absence in some years from long stretches of coast, may be the 

 reason why Hansteen, as mentioned above, has not observed this 

 species on the west coast of Norway. At Christianssund I saw Bangia 

 myself; it grew on an exposed coast up to a few feet above the 

 highest water mark, and was easily distinguishable because of its 

 Hght yellow colour. 



Similar light yellow growths of Bangia may fairly often be found 

 in Denmark and on »Kullen« at the entrance to the Sound. In 

 the Færoes Bangia however always keeps its dark, reddish-brown 

 colour. 



According to Gran, Bangia is the alga growing at the greatest 

 height above the sea-level in Christiania Fjord; it is not so in the 

 Færoes, where several algæ are found at a much greater height. 



However much the two algæ treated in this section may differ, 

 they agree very well biologically and form a very characteristic 

 association, whether growing in the same locality, or, what is also 

 frequent, each in its place forming a Bangia-, and an Urospora- 

 facies. Intermingled with Urospora a great many Ulothrix flacca 

 and other species of Ulothrix are found. 



According to H. Jonsson, Urospora is in autumn and winter 

 partly replaced by species of Ulothrix and Codiolum, which may 

 each of them form extensive associations. 



On the coasts of Greenland, Rosenvinge (71, p. 201) has ob- 

 served a very similar association, composed of Monostroma groen- 

 lundicum, Ulothrix flacca, Urospora mirabilis and Bangia fusco- 

 purpurea. Thus it is also here formed by thread-like, branchless 

 algæ, as pointed out by Ro s en vinge. He calls it the Monostroma 

 g roenlandicum- formation. 



The Fucaceæ-Formation on exposed coasts. 



This formation is found spread, but very commonly on all 



the exposed coasts of the Færoes, even in the most exposed 



piaces, as for instance Store and Lille Dimon, Mj'ggenæsholm, 



the west coast of Sudero, Viderejde, Sumbo Holm, etc. It prefers 



