713 



coasts of the Færoes. Ceiiain bluish -green algæ and perhaps 

 Hildenhrandia excepled, this is the algæ -vegetation which extends 

 the farthest upwards on bare rocks, on which, with the exception 

 of lichens, an inland vegetation mav only be found at a consider- 

 able height, in very exposed piaces, never less than several feet 

 above the level of the sea. On exposed coast this formation there- 

 fore may be found many feet above the level of the sea; on the 

 west coast of Vaago, at Bosdalafos, the outlet of Sorvaagsvandet, 

 at the time of year when the sea is calmest, that is, in June and 

 July, above the cataract, consequently about 80 feet above the 

 level of the sea, in moist cracks in the rocks shaded from the 

 sun, I have gathered forms of Enteromorpha intestinalis and Rhizo- 

 cloniiim ripariuin, which are characteristic of the formation under 

 discussion. 



As a matter of course the algæ belonging to this formation 

 must be able to do without water, and to be washed by fresh 

 water. Some, but not quite all these species, may also be found 

 under certain forms growing in more or less brackish water. They 

 generally grow so far above the level of the sea, that they are 

 only reached by the surf and the spray, and if the sea be calm 

 for some length of time, which may sometimes happen, especially 

 in summer in the very changeable climate even of the Færoes, 

 they are totally prevented from being moistened by salt water. On 

 the contrary they are at times soaked by fogs and rain to such a 

 degree, that they are most probably completely deprived of salt. 

 Some few of the algæ belonging to this formation moreover grow^ 

 in localities where fresh water oozes from the rocks. On the other 

 band several of these algæ may in dry weather and sunshine appear 

 to dr}' up, some of them, e. g. Prasiola crispa subsp. marina, Prasiola 

 stipitata and Enteromorpha intestinalis even so as to be easily pul- 

 verised. As to Rhizocloninm riparium, 1 have not found it dry; it 

 generally occurs on wet rocks and thus always keeps rather moist. 



The algæ belonging to this formation must moreover be 

 able to stand the full day and sunlight, as they grow on rocks 

 facing south as well as north. On the other band they are less 

 in danger of being injured by the surf, as they most often grow 

 so far up that only the spray can reach them. When they grow 

 farther down, it may be supposed that the low, dense, often very 

 gregarious growth of, for instance, Prasiola stipitata and P. fiirfiiracea 

 and Enteromorpha, serves as a means of protection from the dashing 



