Clare Island Survey — Marine Algae. 15 25 



Himanthalia), and forms a broad band extending down to the Laminaria 

 level. It appears to enjoy moderate wave-action, but requires flat rocks, 

 and disappears at once where the rocks are steep or the exposure too 

 great. This form of fucaceous growth occurs typically on the slopes near 

 Kinnacorra, near the Castle, and at several spots on the south shore, 



With greater shelter further differences are evident. Pelvetia and 

 F. serratus remain as before, but F. spiralis broadens out into var. platycarpus 

 and F. vesiculosus develops more vesicles, the length of both species increasing 

 and assuming the heavy bulky growth characteristic of sheltered coasts. The 

 horizontal distribution also of all the species tends to increase, owing to the 

 shore being usually flatter. Such growth occurs in several bays on the island, 

 and is common in more open parts of Clew Bay. Ascophyllwm nodosum requires 

 considerable shelter ; and in Clare Island it is present in one spot only, namely 

 Ooghbeg on the south shore. The shore here is rather flat, and the force of 

 the waves is broken by the presence of blocks and boulders. At Portlea (parts 

 of which might appear to be equally sheltered) Ascophyllum is absent, but the 

 presence of a vigorous Himanthalia vegetation indicates greater exposure 

 than might be supposed. For further notes on this species see p. 55. 



Epiphytes. — The typical epiphytes of the exposed Fucus association are as 

 follows, and in the most exposed spots these are practically all that occur : — 



Ulothrix pseudoflacca (in spring). Elachista fucicola. 



Enteroniorplia compressa. Porphyra umbilicalis. 



Ectocarpus luteolus. 



Where the conditions are less boisterous (e.g. at Kinnacorra) a number of 

 other species occur in addition, for example — 



Ectocarpus tomentosus. Polysiphonia fastigiata (on F. spiralis). 



E. fasciculatus. Ceramium rubrum. 



Porphyra leucosticta (in spring). C. Boergesenii. 

 Bhodymenia palmata. 



Subvegetation.— This, though always better developed in the lower than in 

 the upper levels, is largely dependent on the denseness of the Fucus growth, 

 i.e. on the amount of room and light available. When conditions are favour- 

 able, the first four of the following communities are usually represented, and 

 the last three are occasionally present in addition : — 



Hildenbrandtia- Verrucaria Association. Lichina pygrnaea Association. 



Porphyra umbilicalis ,, Bhodymenia palmata ,, 



Laurencia pinnatifida „ Lithothamnium Lenormandi Society. 



Corallina spp. Society 



B, I. A. peoc, vol. xxxi. D 15 



