Clare Island Survey — Marine Algae 15 39 



on a sloping shore is between the Laamwia piniudijidu beltand the Laminaria 

 association. 



In the form of a narrow band, the Himanthalia vegetation is seen on the 

 south shore of Clare Island in spots where the rocks are steep, and there is 

 full exposure to the waves ; as a wider zone, it shows well on rocks which form 

 large sloping slabs, as at Kinnacorra. At Portlea a more extensive growth is 

 met with. The shore here is flat, but there is a moderate amount of rough 

 water and surf. A dense undergrowth of Zaurencia pinnatifida and other 

 algae covers the lower part of the littoral region, and on this the Himanthalia 

 lies as a thin covering. The belt, however, is not so deep as it appears ; for, 

 although during spring-tides it is left dry for three or four hours, during 

 neap-tides the time of exposure and the amount uncovered are small. The 

 undergrowth conserves moisture, and enables the alga to ascend to a higher 

 level than otherwise. Portlea also affords an example of another type of 

 growth, viz., that on blocks and boulders. In this ease Himanthalia is 

 attached to the upper parts of the boulders ; but the strap-like fructifications 

 hang down over the sides (see PI. II). Here again the alga may ascend 

 above its normal limit owing to the shade between the boulders. 



Borgesen remarks that, according to Boye, Himanthalia avoids localities 

 directly exposed to the surf, which is in contrast to its habit in the Faeroes. 

 In the British Isles it is certainly a surf-loving species ; and in Clare Island 

 it occurs along the south shore, and also on such exposed points as Alnahaskilla. 

 At Ooghbeg, the one spot on Clare Island where Ascophyllum exists, 

 Himanthalia is found where the waves break at low-water ; but as a rule, if 

 there is sufficient shelter for Ascophyllum, Himanthalia is absent. As noted 

 by Borgesen, the present alga cannot stand desiccation ; and though odd 

 plants are seen some half-way up the shore, they do not thrive unless 

 protected from the sun. As a pool-plant it is one of the commonest species, 

 and is then usually infested by Ectocarpis fascicidatus, Ceramium Bocrgesenii, 

 and Herponema vehdina. In the open, Elacliista scutulata is the usual 

 epiphyte. 



Corallina and Lithothamnium Associations. 



A belt of Corallina spp. is found just above low-water mark in many parts 

 of Clare Island. It is characteristic of very exposed rocks, where it appears 

 to take the place of the Laurencia pinnatifida band of less open spots. An 

 extensive growth of encrusting algae is usually met with as an under- 

 growth, and the two types of vegetation appear to be intimately connected, 

 and may for the present be treated together. 



