716 



The Porphijra- Association . 



This association is foiind under the Chlorophycece-iormaVwn, but 

 still on exposed coasts far above tlie level of the sea, 40—50 feet, 

 perhaps even more. It is widely spread along the coasts of the 

 Færoes, on which it extends as a helt often many feet broad. 



In much exposed piaces it extends to far above the level of 

 the sea ; at Bosdalafos on the west coast of Vaago to at least 40 

 feet. On the north western side of Videro, I visited a rock (see 

 plate XIII) about 30 feet high which was quite covered by Porphijra 

 umbilicalis. On the islet of Myggenæs, where the southern side of 

 the rocky coast slopes gently upwards, Porphyra certainly extends 

 up to at least 50 feet above the level of the sea. These observations 

 were moreover all made in summer time; in winter, when the surf 

 reaches much farther up the coast, it is most probable, that Por- 

 phyra also grows at a greater height. 



With the exception of the Hildenbrandia-formnt'ion, which here 

 often forms a subvegetation, and of some species belonging to the 

 C/i/orojo/iyceæ-formation, Porphyra umbilicalis is almost predominant 

 in this association. Porphyra umbilicalis covers the rocks, sometimes 

 densely, sometimes more sparsely. It grows in small tufts, 2 to 3 indies 

 high, whose convolutions gives them the appearance of crumpled 

 paper (see Wi Ile 85, p. 38). The colour of this vegetation is a dark 

 reddish-brown ; sometimes, however, more purpie, sometimes more 

 tawny. On account of its crumpled nature Porphyra umbilicalis 

 can retain sea-water for some length of time among the many 

 folds of its thailus. If the exterior of the plant looks dry, there 

 is, however, often some moisture left between the interior parts 

 of the thailus and those parts which turn downwards. Neverthe- 

 less it can stand to become so dry, that it will creak when trodden 

 upon. It is not only liable to be dried up, but also to being 

 soaked in fresh water, i. e. by rain, for a long time. It is 

 probably protected from the surf by the elasticity and toughness 

 of its thailus, and by the lubricity of its surface. In more sheltered 

 piaces Porphyra umbilicalis becomes higher, often to one foot or more, 

 and its large, curling membranes then cover the rocks or hang down 

 vertical rock-sides like long tufts swaying in the wind (see plate XVII). 

 In sheltered piaces of this kind it likewise grows far down into the 

 littoral region. 



As before mentioned, this association generally only consists of 



