726 



mark in the Færoes, and, according to Boye, at the same height 

 on the west coasl of Norway. 



This association is typically represented by Callithamnion ar- 

 biisciila and Ceramiiim acanthonotum, which are almost always found 

 together on exposed coasts and which are about equally com- 

 mon. On more sheltered coasts, Callithamnion arbnscula is often 

 wanting, as it clearly prefers an exposed coast; and Si m mons, who 

 declares himself (78, p. 250 and 273), that he has not had much op- 

 portunity of investigating exposed coasts, and who has therefore 

 not met with Callithamnion arbnscula, consequently calls this asso- 

 ciation the Ceram/H/n-formation. 



These algæ form small, dense , reddish-brown tiifts, 2 to 

 4 indies long, and are attached either to the Balanus or to the rock 

 itseif, now forming a scattered growth, now a dense covering. On 

 account of their ample ramification and their dense, compact growth, 

 they look almost spongeous, and at high tide they really absorb 

 water which is retained by their capillary action during low tide. 

 After having been laid bare for several hours, they are still so full of 

 water that it can be wrung from them as from a sponge. Kjellman 

 has already (46, p. 479) briefly mentioned this faet. Berthold 

 speaks in a similar way about Callithamnion granulatum, which 

 has been found a few times on the coasts of the Færoes, together 

 with C. arbnscula and much resembling the latter in its habits. He 

 wTites in the following way about it (5, p. 406): »Bemerkenswerth 

 sind in dieser Hinsicht die dichten Thallome von Callithamnion gra- 

 nulatum mit sparrig gespreizten Åsten, welche sich wie ein Schwamm 

 mit gr6sserenWassermengenYollsaugen,wodurcheinAustrocknenauch 

 nur der peripherischen zarten Spitzen vollståndig verhindert wird.« 



In less exposed piaces, this association hardly reaches above 

 the highest tide mark, but in much exposed piaces it may extend 

 far above it. At Viderejde on a rock lying off the landing place, I 

 found a well-developed Co//z7/7am/?zo/j-association reaching to several 

 feet above the extreme tide mark (see plate XV). Here it grew on 

 steep, sloping rocks; besides the two characteristic algæ, a few Por- 

 phyra umbilicalis and several Himanthalia lorea grew here, the latter 

 however being fructiferous only at the lower part of the association. 

 There were, moreover, Acrosiphonia albescens and Polysiphonia urceo- 

 lata, both fitted for retaining water by their dense, felt-like growth, 

 together with Ceramium rubrum, Dumontia filiformis, Scytosiphon 

 lomentarius, Phyllitis zosterifolia, a few small Alaria esculenta and. 



