710 



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

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

 the Faeroes, the Himanthalia -ixssoc'miion of this region distinctly 

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

 one or two feet of the A/ana-vegetation growing under Himanthalia, 

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

 littoral region; Rosenvinge moreover reports, that portions of the 

 Lamznarza-vegetation, which naturally belong to the Laminaria-ioima- 

 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 verv difficult to make a 

 natural division of the algae -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 Tonsbergfjord Gran, for the western 

 part of the Baltic Sea Reinke, for Bohuslan Kj ell man have 

 made use of certain characteristic species growing within well- 

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

 »0stersj6n'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 dilTerent depths in different 

 parts of the sea. 



It is for instance a well-known fact, pointed out by Kj ell- 

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

 way are sublittoral on those of Bohuslan, 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 

 Faeroes 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 Laminarice as 

 Kj ell man has done on the coasts of Bohuslan, it would be very 

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

 within the area mentioned, as the Laminaria /Vieroe/iszs- association 



