710 



I likewise agree with Rosen vinge in stating, that it ouglit to be 

 drawn somewhat above the lowest ebb-mark. On the coasts of 

 the Færoes, the ////7ja/?//ja//a- association of tliis region distinctly 

 marks the limit. At very low tide a rather large portion, up to 

 one or two feet of the i4 /ar/a-vegetation growing under Himanthalia, 

 may sometimes be dried, but this undoubtedly belongs to the sub- 

 littoral region; Rosenvinge moreover reporls, that portions of the 

 Lomz/?a/'za-vegetation, which naturally belong to the Laminaria-^orma- 

 tion growing below that, are likewise uncovered at low tide in Green- 

 land. The lower limit of the littoral region must therefore be fixed 

 at about the ebb mark at neap-tide. 



On tidal coasts it is therefore not very difficult to make a 

 natural division of the algæ- vegetation into a littoral and a sub- 

 littoral region, but on non-tidal coasts the determination of these 

 regions is much more difficult. Attempts have been made to define 

 the limits in other ways; for Tonsbergtjord Gran, for the western 

 part of the Baltic Sea Reinke, for Bohuslån ^ Kjell man have 

 made use of certain characteristic species growing within well- 

 defined limits in the localities in question. In his valuable work on 

 »Ostersjon's Hafsalger«, Svedelius (79) is however certainly right 

 in objecting that this division is anything but satisfactory, as one 

 and the same species may grow at very difTerent depths in dilTerent 

 parts of the sea. 



It is for instance a well-known faet, pointed out by Kjell- 

 man, that many algæ which are littoral on the west coast of Nor- 

 way are sublittoral on those of Bohuslån, where the fresher surface 

 current does not reach them. Svedelius therefore is certainly right, 

 when he warns us against drawing a parallel between the regions 

 belonging to heterogeneous flora domains, as the factors which in 

 one place justify a very distinct division into regions and make a 

 limit for the occurrence of a species, may be totally wanting in 

 another. 



As I have already explained in the introduction, there is in the 

 Færoes a small tract of the sea between Ostero and Stromo where 

 the tides are almost imperceptible. Here the question is where to fix 

 the limit between the two regions. 



If the limit be fixed at the beginning of the Laminariæ as 

 Kjellman has done on the coasts of Bohuslån, it would be very 

 easy to point out a very distinct line between the two regions 

 within the area mentioned, as the Laminaria /æyoenszs- association 



