MARINE ALGAL VEGETATION 143 



(f.pinnata). This alga is one of the largest found on the coasts of 

 Iceland, and may at times attain a length of 6 8 metres. The form 

 of the frond resembles to some extent the shallow-water form of 

 Laminaria saccharina, the thick mid-rib of Alaria corresponding with 

 the thickened median area of Laminaria. The fronds of both species 

 are thus well adapted to withstand the motion of the waves; in 

 fact both species are rather frequently found intermingled in a broad 

 belt along the coasts. On many of the sunken skerries which are 

 such a danger in navigation, Alaria esculenta is the principal species, 

 indeed frequently growing alone. In Hvammsfjor5ur in SW. Iceland, 

 in places where a strong current exists (Rostin) there was found a 

 dense vegetation of broad-fronded Alaria esculenta f. pinnata with 

 very long laminae. 



It is general knowledge that the lamina is torn in pieces by 

 the waves, and cases are frequent also in which the thin part of 

 the lamina is divided into many pieces by transverse slits, often 

 nothing remaining save the mid-rib itself, especially in the upper 

 part of the lamina. A luxuriant Alarietum was found below the 

 limit of low r -tide at the extreme point between Sey5isfjor5ur and 

 Lo5mundarfjor5ur; it consisted mainly of Alaria esculenta f. pinnata 

 with Alaria Pylaii and Lam. saccharina intermingled. It was at once 

 noticeable that the uppermost Alaria* were entirely frondless; the 

 stipes were completely overgrown with Ectocarpacece. It must be 

 admitted that the situation was exposed, and therefore it may well 

 be that the laminae were destroyed by the beat of the waves; but 



*/ / 



there is just as much reason to believe that this was occasioned 

 by the drift-ice, which had made its appearance on the coasts some 

 time before my arrival. In this locality the Fucus-bell had also 

 been scraped off the rocks in several places which, in my opinion, 

 was caused by the drift-ice. 



The Laminaria saccharin a-association. This associa- 

 tion is very luxuriant, and occurs almost pure over stretches ex- 

 tending for miles along the coasts. It does not always grow on a 

 firm , rocky substratum : rather frequently it occurs on a pebbly 

 substratum , in which case the plants are attached either to a 

 single pebble or to several, as if lying at anchor. With dredgings, 

 therefore, it rather frequently happens also that the plants 

 with their "anchors" are dragged up from the sea -bottom. This 

 association is met with from a depth of about 2 metres, or from 



