15 2 Proceedings of the Royal Irish Academy. 



variety of ground in the neighbourhood provided ample scope for the modern 

 study of plant-communities. The position of the island — off the coast of 

 Co. Mayo, and in the Gulf Stream drift — ensured the presence of that 

 southern element which gives the Irish flora its peculiar interest. 



The following report shows that the hopes raised have been amply 

 fulfilled. The flora proved quite as rich as was expected ; and practically all 

 the species for which the west of Ireland is noted occur within the survey- 

 area. Valuable systematic results have been obtained ; and the variety of 

 algal associations present rendered the study of the marine vegetation one 

 of the most comprehensive that has yet been carried out. Important 

 phytogeographic data also, necessitating the modifying of previous views, 

 were secured. 



INTRODUCTION. 

 1. — Definition of the Area. 



Owing to the comprehensive nature of a natural history survey, the 

 limits of the area investigated varied in different eases, since in some it was 

 advisable to include a much larger area than in others. With regard to the 

 marine algae, it was thought best to limit the investigation to Clare Island 

 and the neighbourhood of Clew Bay. By concentrating attention on a small 

 district a more accurate knowledge of the true nature of the vegetation can 

 be obtained, and the variety of ground presented in the area mentioned 

 proved quite as much as was possible to work with a moderate degree of 

 thoroughness. 



The Survey-area for the algae, therefore, consisted of Clare Island, the 

 shores and waters of Clew Bay, and an extension to the north to include 

 Bellacragher Bay and Achill Sound. 



At the same time it appeared advisable not to overlook the interesting 

 records from Eoundstone, a locality only twenty-five miles south of Clew Bay. 

 This district was carefully worked some seventy years ago by W. McCalla, 

 and he collected several species which were not found in the Clare Island 

 district. A brief visit was paid to Eoundstone ; and all records from that 

 locality are included in the report. 



2.— Previous Work in the Area. 



According to the scheme of geographical areas devised by Adams (see 

 Adams, '11, in Bibliography) the province of Connaught is divided into three 

 sub-divisions. Co. Mayo (which includes the survey-area proper) forms sub- 

 division C 2, and, according to an annotated copy of Adams' Synopsis (Adams, 



