. — 



150 H. JONSSON 



Laminariacece. It occurs most commonly at depths of from 6 — 20 

 metres, but has also been found as deep as 30 metres. 



Many of these species grow very socially and often cover the 

 stipes completely, or nearly so. At Reykjavik, it is very usual in 

 the spring to find Laminaria hyperborea in shallow water (4 — 10 

 metres) with the stipes entirely overgrown by Rhodochorton Rothii, 

 Antithamnion floccosum and Polysiphonia urceolata, each on its own 

 particular stipe, or else intermingled. Petrocelis and Rhododermis 

 occur also in great abundance, almost covering entire stipes. In the 

 Vestmannaeyjar and at Eyrarbakki it was also a fairly common 

 occurrence to find stipes of Laminaria hyperborea completely over- 

 grown by Dermatolithon macrocarpum. In the northern part of the 

 country Lithophyllum Crouani also sometimes covers the stipe of 

 L. hyperborea over its entire length. Many of the remaining species 

 may also occur abundantly, but most frequently the vegetation upon 

 the stipes is mixed, and crustaceous species grow side by side with 

 branching and membranaceous species. 



The epiphytic vegetation seems to be most luxuriant and richest 

 in species at lesser depths, where the semi-littoral associations 

 meet the associations which extend deeper down, and where, in 

 addition to the Rhodophycea? which always predominate, both brown 

 and green species occur. At a greater depth the species are few, 

 and are almost exclusively Rhodophyceo?. Generally, the rule seems 

 to hold good that while the species with a more downward range 

 occur on the haptera or on the lower part of the stipe, the more 

 light-loving species occur on the upper part of the stipe; the green 

 algae, however, are by no means always uppermost. Thus in the 

 upper portion of the Laminaria-be\t Euthora, Rhodophyllis, Odon- 

 thalia and others frequently occur among the haptera, but in the 

 lower portion of the belt they may be found on the stipe almost 

 everywhere, especially Euthora. This agrees with Bert hold's ob- 

 servation of the succession of epiphytes on Cystosira in the Medi- 

 terranean, and with Borgesen's observation of the order of the 

 epiphytes on Laminaria hyperborea in the Faeroes. 



The vegetation on the stipe of L. hyperborea is extremely 

 luxuriant in S. and SW. Iceland and is considerable both in NW. 

 and N. Iceland, but is poor in E. Iceland. 



Epiphytes frequently occur also on the fronds of the Lami- 

 nariaceai , especially in the upper portion of the Laminaria-helt. 

 Here the brown algae predominate, while only a few red and green 



