Glare. Island Survey — Marine Algae. 15 75 



The above vegetation characterizes much of the inner part of Clew Bay. 

 At times it forms an undergrowth to the pebble-attached association ; but as 

 a rule it appears to exist as a separate community, except for a certain 

 admixture of BJwdochorton floridmlwn and Sphacelaria cirrhosa. In winter 

 Gordylecladda ereeta is also plentiful. The February visit was most useful in 

 obtaining fruiting material, but even then many of the Brown encrusting 

 plants proved sterile. A January visit would perhaps have been more 

 productive. Outside the islands the species mentioned mostly disappear, the 

 rocks and stones being clothed with plants which belong rather to the exposed 

 Lithothamnium association (e.g., L. laevigatum and L. compactum). 



It is difficult to compare the Clew Bay growth with that of other localities, 

 especially with regard to the relative abundance of the different algae, but it 

 appears to be richer in species than any of the Lithoderma associations 

 hitherto described (Kjellmann, '78, Borgesen, '05, Kylin, '07). In England 

 much dredging has been done by various workers, and Plymouth Sound, 

 which is as sheltered as Clew Bay, has been well explored. The records, 

 however, are poor, and there is no means of satisfactorily comparing the 

 vegetation. It is interesting to note that Harvey dredged Peyssonnelia 

 abundantly in Birturbuy Bay, whereas in Clew Bay Gruoriella Dubyi is by 

 far the most frequent species. 



Channel Vegetation. 



On each visit a record was kept of the species collected in the shallow 

 channels at Aehill Sound. Though far from exhaustive, the lists serve to 

 indicate the most conspicuous algae during the different seasons of the year, 

 and since no record of the seasonal development of this type of vegetation 

 exists, they appear to be worth}' of publication. Kuckuck ('97) briefly 

 describes the seasonal variation in Heligoland ; but his paper deals with an 

 open shore. It will be noted that the flora of the channels resembles that 

 of the pebble-attached association of quiet bays— a fact which is not surprising, 

 since the general surroundings are similar, and in both cases the plants are 

 attached to stones on sand. In the channels, however, there is rapid current, 

 whereas in the bays the water is slack. The accompanying table comprises 

 lists of the four seasons of the year : — 



K2 



