Clare Island Survey — Marine Algae. 15 49 



Ireland, and it probably only occurs where great exposure is coupled with 

 a wet, foggy climate. " • 



The usual epiphytes characteristic of the species occur. Litosiphou 

 Ala viae, Ectocarpus fasciculatus, and Myrionernaceae are frequent on Alaria — 

 Chaniraiisia Alariae rare. The laminae of L. digitata commonly bear 

 a copious growth of Ectocarpi, Ceramia, Callitharaaion tetragonum, and 

 other small plants, while the stipes are usually clean. The rugged stems of 

 L. Cloustoni, on the other hand, are densely clothed with Florideae, which 

 show a tendency to definite sequence from above downwards as pointed 

 out by Berthold ('82) and Borgesen ('05). As a rule this sequence is as 

 follows : — 



Ehodymenia palmata. 



Polysiphonia urceolata. 



Delesseria sinuosa. 



Delesseria alata. 



Heterosiphonia coccinea. 



But in addition to the differences due to seasonal variations many irregulari- 

 ties were noted. Other characteristic epiphytes are : — 



Codium tomentosum. Ptilothamnion pluma. 



Callophyllis laciniata. Ptilota plumosa. 



Ehodymenia palmetta. Plumaria elegans. 



Lomentaria articulata. Rhodochorton parasitica. 



Plocamium coccineum. Craoriella Dubyi, r. 



Nitophyllum laceratum. Cruoria pellita r. 



N. uncinatum (autumn). Petrocelis Hennedyi r. 



N. Bonnemaisoni, r. Dermatoiithon pustulatum. 



Saccorhiza is usually fairly clean, as is also L. saccharina in exposed 

 localities. 



Comparison with other Countries. — As far as Alaria, L. digitata, and 

 L. Cloustoni are concerned, the above vegetation agrees well with that 

 described by Borgesen for the Faeroes, though in that region it ascends 

 somewhat higher on the shore. Saccorhiza is entirely absent; but this is 

 compensated for by the presence of two additional species, A. Pylaii and 

 L. faeroensis, the latter being confined to sheltered coasts. Borgesen, in an 

 interesting paragraph on the effect of wave-action on Laminariae, points out 

 that the pliable stipes and fronds of Alaria and L. digitata are able to resist 

 the violent conditions of a steep shore, and where the breaking of the waves 

 is felt ; whilst the stout and comparatively rigid steins of L. Cloustoni are 

 suited to the strong pull of the rollers in deeper water. 



R.I.A. PROC, VOL. XXXI. G 15 



