Pethybridge & PiiAEGEK — Vegetation South of Dublin. 145 



Pferis is also occasionally found in abundance in the moorland 

 amidst the heather, and so are large patches of Juncus effusm, J. acuti- 

 florus, and their associates; while in one place, along the scarp overlook- 

 ing the two Loughs Bray, a Vacmiiiim association is well developed. 

 Finally, in this zone we have one or two large areas, as near Prince 

 William's Seat and on the summit of Kippure, where the living vege- 

 tation is conspicuous by its absence, and where, owing probably to slow 

 climatic changes, the peat is being denuded away, leaving the bare 

 crumbling granite exposed. (Plate XI., fig. 2.) 



The wooded areas in our district are comparatively few and small ; 

 but what there are, are distributed in all the zones mentioned above, 

 except the littoral zone. 



The Littoral Zone. 



As pointed out before, the maritime vegetation as developed along 

 the coast in our area is not an extensive one; the richness in mari- 

 time plants which characterizes this zone in the County Dublin, as a 

 whole, being better developed along the northern part of the coast- 

 line of the county. The zone, however, may be considered as being 

 occupied by tiie three associations which follow, the first of which alone 

 covers an area sufficiently extensive to be recorded on the map. 



The Sand-Dune Association. (L.)^ 



This is only developed to a small extent in our area, namely, at 

 the South Bull, south of the Pigeonhouse Fort, at the entrance to 

 the Piver Lifiey. The limited amount of sand-dune here is of the 

 loose type of dune, with an open vegetation, and there is a complete 

 absence of any grassy or mossy sward. Triticum junceum is easily 

 recognized as being the most abundant plant, seeming especially to 

 thrive on the lower ridges of the sand-hills, and apparently not 

 suffering in the slightest from an occasional inundation of salt-water. 

 Psamma arenaria is more conspicuous on the higher parts of the 



^ The letter given after the name of each association corresponds with that 

 used on the map published herewith. 



