110 H. JONSSON 



This belt behaves similarly in the Faeroes (Borgesen, 12, p. 

 744). Both Boye (10) and Hansteen (25) mention a Pelvetia-forma- 

 tion from western Norway without mentioning Fucus spiralis. In 

 Finmark Fucus spiralis has the same manner of growth as in Ice- 

 land (F os lie, 18, p. 66). 



The Fucus-belt. 



The four associations which belong to this belt are the most 

 extensive in the littoral zone and three of them are found everywhere 

 on rocky coasts. The breadth of the belt naturally is dependent on the 

 degree of the declivity of the coast in addition to the nature of the 

 substratum. This belt occurs everywhere along the coast, but it is not 

 luxuriant to the same degree everywhere. Its vegetation is so dense 

 that the bottom is entirely covered, or almost so, by the Fucus 

 plants which during low-tide partly lie prostrate upon the rocks 

 and partly hang on them; seen from a distance it appears as a 

 brown-coloured belt of varying width along the coast. These asso- 

 ciations are usually found on a rocky substratum, but they may 

 also occur on a fairly firm gravelly bottom; the latter is especially 

 the case at the head of the fjords. In such places their vegetation 

 is poor and the species grow scattered, attached especially to small 

 stones which are somewhat firmly embedded in the gravelly bottom. 

 Fucus plants are also found scattered on wood-work, for instance, 

 on wooden piles. On the whole the species of Facus require a 

 stable substratum. The dominant species are the following: 



Fucus vesiculosus. Fucus inflatus. 



Ascophyllum nodosum. Fucus serratus. 



The first three species are common and grow very luxuriantly 

 along the coast; Fucus serratus, on the other hand, was found only 

 in a few places in S. and SW. Iceland; in Hafnarfjordur it grew 

 very socially, while in the Vestmannaeyjar it had a more scattered 

 growth. 



The individuals of these species form pure associations which 

 usually occur in regular succession: Fucus vesiculosus growing upper- 

 most, Ascophyllum in the middle and Fucus inflatus (and Fucus 

 serratus) lowest of all. This succession is distinctly observable in 

 places where the bottom is flat and gently sloping. But where the 

 bottom is uneven a talus of debris the divisions between the 

 belts are less regular, but can, as a rule, be discerned. It does not, 

 however, follow that the associations always occur quite regularly; 



