MARINE ALGAL VEGETATION 141 



character of the community in sheltered and in exposed places, 

 which is evident from the description of the association given he- 

 low. In sheltered places the calm -water character predomi- 

 nates; to this belong the Saccorrhiza dermatodea- association, the 

 Alaria Pylaii- association, the Laminaria fceroensis- association and 

 the calm-water associations of L. saccharina and L. digitata. Of the 

 very much exposed associations, the only essential one to he re- 

 corded is the S/e/?o/?/?y//a-association (see under L. digitata). In ad- 

 dition, a difference is evident according to the depth, and the as- 

 sociations then occur either with a shallow- water character 

 or with a deep-\vater character (see below). 



In its main features, this community occurs in a similar man- 

 ner on the coasts of adjacent countries. The communities of S. and 

 SW. Iceland greatly resemble those of the Faeroes, as has been fre- 

 quently mentioned, and also those of western Norway (Boye, 10; 

 Hansteen, 25) and of Finmark (Foslie, 18). 



The Saccorrhiza dermatodea-association. I have most 

 frequently found this species just below the limit of low-tide, where 

 it is of medium size, and grows scattered. In water-filled depres- 

 sions in the lowest part of the littoral zone which, although they 

 lie above the limit of low r -tide, belong from a biological point of 

 view to the lower-lying area, the species is often very social and 

 forms pure associations. I have found it growing very socially at 

 a greater depth (22 28 metres) within Rey5arfjor5ur in E. Iceland 

 off Holmanes or thereabouts ; the specimens which occurred there 

 were of large size. When the various Ectocarpacew which may occur 

 on old individuals are excepted, the plants are usually free from 

 epiphytes. The association develops best in somewhat sheltered places. 



The Alaria Pylaii-association. Alaria Pylaii, as mentioned 

 below, often grows interspersed amongst Alaria escnlenta f. pinnata, 

 Laminaria saccharina and others, in somewhat exposed places; but 

 its real habitat is in the interior of the fjords, where the water is 

 calm. Here occur the typical, large, broad-fronded individuals: they 

 are often social in growth and then form pure or almost pure as- 

 sociations; but they are most frequently distributed in patches, and 

 then alternate with Saccorrhizeta or social growths of Laminaria 

 nigripes v. atrofulva. In such places occur also the broad-fronded 

 calm-water forms of Laminaria saccharina and L. digitata. Alaria 



