1907. Prakger. — Phanerogams, &c., of Lambay. 91 



Plant Associations. 



The plant associations which cover the surface of Lambay 

 are in general distinct and well defined, with tolerably sharp 

 boundaries. These boundaries are in part natural (the effect 

 of variation of the ecological factors which control the 

 vegetation) and in part artificial (the result of farming 

 operations). Following on the halophile flora of the beaches 

 and sea-cliffs, the three main associations of the island exhibit 

 in general a zonal arrangement according to altitude — namely 

 (in ascending order), grass land, bracken, and heath (see 

 Plate 22) ; but this order is not without many local exceptions. 

 The remaining two associations are presided over by Sedum 

 anglicum and /uncus obtusiflorus respectively, and represent 

 opposite extremes as regards the water factor. 



Maritime A ssocia tio?is. 



Except 011 the western side, the ground rises steeply from 

 the water's edge. Even on the west, the flattish grass lands 

 are raised well above tide-level. In consequence, salt-marsh 

 is absent, and the halophile vegetation is confined mainly to a 

 very narrow strip surrounding the island. 



A sandy shore occurs at the harbour, yielding Sea Holly 

 {Eryngium mariiimum), Sea Purslane {Arena? ia peploides), Sea 

 Whin {Salsola Kali), Polygonum Raii, Agropyron junceum, 

 which have here their only station ; elsewhere the maritime 

 vegetation is largely confined to rocks and shingle, and 

 characterized by an abundance of Samphire {Crilhmum 

 maritimum) i Golden Samphire {Inula erit/imoides), and Sea Beet 

 {Beta maritima) (Plate 21). Above this zone, maritime sward, 

 of one type or other, is extensively developed, and forms a 

 characteristic feature of the vegetation of Lambay, rising to 

 no less than 200 feet above sea-level. The main areas which 

 it occupies are along the east side of the island, as shown by 

 the map (Plate 20), and the ornithologist will at once notice 

 that they correspond with the principal breeding colonies of 

 the Herring Gull. There can be 110 doubt that the presence of 

 these birds is, to a large extent, accountable for the peculiar 

 vegetation which here prevails. During the breeding season 

 the plants composing the sward are seen to be much trampled 



