15 S2 Proceedings of the Royal Irish Academy. 



Bostryehia-Catenella Vegetation. 

 The usual growth of Bostryeliia scorpioides and OateneUa Opuntia as 



epiphytes on flowering plants occurs in our area, though not in such profusion 

 as in some localities. 



The former is very plentiful, and is especially found as a dense growth 

 under the leaf-rosettes of Static: maritime. At Mulranny the older plants 

 seldom lack this Bostryehia-pad. On woody plants, such as Atriplex and 

 Limonium (specially when growing at the sides of streams and channels), it 

 hangs loosely from the lower branches. Catenella is, on the whole, scarce on 

 the marsh, but locally it is abundant. 



It is worth noting that both these plants occur near high- water mark on 

 the banks of the Newport Biver, and in parts of the upper reaches of Clew 

 Bay. They grow here on bare rocks and boulders, showing that brackish- 

 water and long exposure to the air are important factors. A certain amount 

 of shade is usually provided by Belvetia. 



Vegetation of Vertical Banks peat or loam). 



The vertical peat-banks which occur on the Annagh Island and Mulranny 

 salt-marshes possess a characteristic flora showing well-marked zonation. The 

 same vegetation is even better developed on the peat-banks bordering on the 

 shores of Achill Sound. On the salt-marsh, the banks are seldom more than 

 3 feet in height, and are much broken up ; but at Achill they are higher, and 

 often extend for some distance along the shore. The same type of vegetation, 

 showing the same sequence, is also found on the loam-banks of the Bunowen, 

 but with certain characteristic differences, due to the presence of fresh water 

 see p. So). The fresh-water channels of the salt-marsh are also distinct, their 

 banks being muddy and possessing a different flora. 



In a general way the vegetation of the peat-banks is disposed in four 

 bands, which invariably occur in this sequence from above downwards : — 



1. Phoeococcus adnatus. 



2. Bivularia nitida. 



?. Vaucheria coronata and Calothrix fasciculata. 



•A. Ehizoclonium ripaiium (with scattered plants of F. spiralis, var. nana). 



The three lowest bands are usually each about 1 foot deep; but the 

 Phoeococcus band is narrow, and is not infrequently absent. Practically all 

 the tidal banks are clothed with this vegetation; but at times (especially 

 where moisture is retained ?) a growth of F. vesiculosusvar. mv.scoid.es intrudes 

 from the grass above. The essential conditions appear to be regular flooding 

 with salt-water, coupled with complete shelter. 



