Clare Island Survey — Marine Algae. 16 47 



Lenormandi and L. polymorphum being the most usual. The pool-flora 

 consists chiefly of the following species : — 



Phyllophora rubens. Polysiphonia urceolata. 



P. meinbranifolia. Chylocladia articulata. 



Rhodymenia palniata. Griffithsia setacea. 



Nitophyllum laceratum. Pterosiphonia parasitica. 



Delesseria sanguinea. Lithophyllum incrustans. 



Plocamium coccineum. Lithothamnium polymorphum. 



(b) A small tunnel-like cave on the south side of Portlea was carefully 

 investigated each season. Though short, it was the only really dark cave 

 examined, and its flora proved of considerable interest, three of the rarest 

 algae of the island occurring in it. Near the mouth of the cave the shaggy 

 growth lining the walls consisted of Cladoph&m rwpestiHs (dominant) and 

 Plumaria (sub-dominant), with the following species scattered freely amongst 

 them : — 



Ectocarpus Holmesii. Polysiphonia macrocarpa. 



Gelidium pusillum. Rhodochorton floridulum. 



Rhodymenia palmata. Callithamnion scopulornm. 



Polysiphonia urceolata. Spermothamnion Turneri. 



A little further in, Plumaria becomes dominant, and, with the exception of 

 Cladophora rupestris, which assumes a thin feebly branched habit, the other 

 algae gradually disappear. On the bottom and at the margins of pools, 

 Derbesia marina is found, and on the sloping sides Codium amphibium under 

 the drip of fresh water. At the further end, the walls are mostly clothed with 

 a pure growth of Plumaria, though patches of Lithothamnium Lenormandi var. 

 squamalosa exist, and Derbesia occupies the water-edges. The pool-flora is 

 remarkable ; Plumaria, Ceramium acanthonotum and Polysiphonia macrocarpa 

 are common, whilst further in there is a felt of the minute Ptiluthamnion 

 hwifugum (sp. no v.). 



(b). Sub-littoral Region. 



The sub-littoral vegetation of exposed coasts is difficult of exploration. In 

 calm weather much may be learnt from a boat at dead low water, but in a 

 general way a small boat and a hand-dredge are of little use. Two associations 

 only are described below, these being the only ones which were definitely 

 investigated . Colonies of the beautiful Cystoseira ericoides are plentiful off 

 the shore, in company with such plants as Saccorhrza and Himanthalia, but 

 unfavourable weather baffled attempts at their study. 



