MARINE ALGAL VEGETATION 67 



neither, is any distinct boundary found between the boreal and 

 subarctic floral districts, and the north and north-west of the country 

 must, strictly speaking, be considered a large boundaiy-area, a view 

 which accords well, also, with the hydrographic conditions. Here, 

 the boreal, subarctic and arctic species intermingle. 



At the south-eastern point of Iceland there is , on the other 

 hand, a rather distinct hydrographic boundary along the stretch 

 from Vestrahorn to Eystrahorn (or L6nshei5i). The greater part 

 of this coast is sandy, and difficult of access for the investigation 

 of the algal vegetation. From my own observations I can only say 

 that Berufjor8ur, the most southerly point in E. Iceland which I 

 have examined with regard to its algal vegetation, has a cold-water 

 flora, and that the Vestmannaeyjar, the most easterly locality on the 

 south coast which I have examined for the same purpose, have a 

 warm-water flora. The boundary must lie between them, and I 

 conclude, especially from the hydrographic conditions and the dis- 

 tribution of the Plankton-associations, that it is situated just on the 

 stretch of coast already mentioned. Ove Paulsen (55 and 56) has 

 given valuable information respecting this boundary, and it is 

 evident from his investigations that the boundary varies to a slight 

 extent, the facts being that in May-June it has been found in the 

 vicinity of Eystrahorn (see 55, map I), but in July-August at Vestra- 

 horn (see 55, map II). If algae grow on this stretch of coast, one 

 may conclude that there exists a mixed flora resembling that of 

 N. and NW. Iceland. Whether boreal species can be carried to E. 

 Iceland in this manner is at present not easy to say with certainty, 

 yet it seems to me that the occurrence of Dumontia filiformis and 

 Delesseria sanguinea, both of which are absent in N. and NW. Ice- 

 land, can be most easily explained in this way. 



