Clare Island Survey — Marine Algae. 15 37 



It is interesting to note that, though C.arbusculq was the essential species 

 in Clare Island, specimens of the southern G. gramdqtum. were scattered here 

 and there amongst it. The latter agreed in form with the Dorset specimens, 

 being short, very densely branched, and of a peculiar pale colour — a feature 

 which gives the clue to its presence (see p. 142). 



Hansteen, Boye, and Kylin have each dealt with a vegetation on the 

 west coast of Norway that is probably very similar to that here described, 

 though it is Callithamnion that has mostly attracted attention. Kleen also 

 records both algae from Nordland. In the Faeroes, Simons refers to a 

 " C. acanthonotum formation," not observing the presence of C. arbuscida, 

 whilst Borgesen, exploring the coast more thoroughly, found the latter 

 abundantly in exposed places, and adopted the older term. Both species 

 are found in Iceland, though Jonsson does not allude to them as forming an 

 association. 



Some remarks by Harvey with reference to this vegetation may be quoted 

 here. He observes with regard to C. arbuscida that " it delights in the most 

 exposed rocks and the roughest. water, and very commonly grows on the 

 shells olMytilusriyosus" (Phyc. Brit., pi. 274); and concerning 0. spongiosum, 

 he writes, " It is curious that it appears to occupy the place of C. arbuscida on 

 shores where the latter is not found, these plants never growing together, 

 though both affect similar situations on different shores " (1. c, pi. 125). As 

 shown above, Harvey's statement as to position and habitat of the species 

 holds good for many countries, though the Clare Island work proves that 

 the two species may occasionally occur together. 



Nemalion Association. 



The present vegetation, described by Kjellmann in 1875, was one of the 

 first algal associations to be recognized. It differs from many others in being 

 a purely summer growth, and might therefore be more suitably regarded 

 as a plant-society. The Nemalion belt occurs in the lower half of the 

 littoral region — that part of the shore which is crowded with a succession 

 of algae, and in which many transient societies are recognisable. Nemalion 

 prefers bare rocks, and usually develops in spots devoid of other vegeta- 

 tion. It would probably find a place as a subdivision of BorgeseD's 

 " Corallina formation " ; but in the present state of our knowledge it 

 appears advisable to follow previous writers rather than introduce doubtful 

 alterations. 



The Nemalion growth is first noticeable early in June, reaches its maximum 

 in August or September, and disappears in October. The association in Clare 



