76cS 



mens mav of course be sometimes found, but not in great numbers, 

 what is, however, the case on the coasts of Greenland, according to 

 Rosenvinge (71, p. 218). The name »formation of loose-lying Algæ« 

 may in the Færoes only be used of the above mentioned loose 

 masses of algæ, which mainly consist of species of Enteromorpha, 

 Chætomorpha tortiiosa, Acrosiphonia, Monostroma, etc. 



The Vegetation on soft bottom. The Zostera- Association. 



With the exception of the Characeæ, which may be found in 

 brackish water, algæ from the northern seas will not usually thrive 

 on a bottom of sand or mud^, which is therefore destitute of 

 vegetation. Only here and there, where stones are found, may 

 algæ be met with, but as a soft, loose bottom is rather common 

 in the sounds between the islands and in the fjords, at any rate 

 in deep water, somewhat large, naked regions occur with only a 

 few loose drifting algæ. What makes the tracts still more naked 

 is, that the Zostera marina, which has its habitat in shallow 

 water (down to a depth of from 6 to 7 fathoms in our seas) in 

 this kind of ground with loose bottom, is almost totally wan- 

 ting at the Færoes. It has only been found at the bottom of 

 Vaag Fjord. In a small limited territory it makes an association 

 here at a depth of about 1 fathom, and at low tide, its leaves may 

 be seen floating on the surface of the sea. The Zostera here as 

 elsewhere shelters a number of different epiphytes, e. g. species of 

 Enteromorpha, Ectocarpns litoralis, Chantransia virgatnla and C. secnn- 

 data, Microsijphar Zosteræ, Scytosiphon lomentarins, and so forth. 



3, The Iower limit of the Algæ-vegetation. The elittoral Region. 



As mentioned before, I agree with Ro sen vinge in determining 

 the elittoral region as that part of the bottom of the sea where no 

 vegetation grows on the bottom ; I shall therefore leave this re- 

 gion out of consideration. At far greater depths than those at 

 which the fixed algæ grow, we may of course find loose-lying algæ 

 which have been carried by the current away from their habitats. 

 Such portions of algæ may perhaps live for some time by con- 

 suming their reserve stores, but when these are used up they must 



^ In the tropics however we find an algæ-vegetation which is often qnite 

 dense and fastened on a bottom of sand or mud. 



