15 66 Proceedings of the Royal Irish Academy. 



Of the other species entering into the association Polysiphonia fibrata, 

 Geramium strictum, C. ciliaium form conspicuous patches in spring and summer, 

 their tufts of rhizoids growing down into the sward, and attaching themselves 

 to the sand-grains. C. ciliatum is found more or less all the year round, and 

 is of a shorter and denser habit than when growing in pools. In spring the 

 association often assumes a bright green colour due to the presence of 

 Cladophora arcta. This species retains the sand well by means of hooked 

 branches and rhizoids which grow downwards from the main shoots. It occurs 

 not only within the Ehodochorton vegetation, but outside it, often forming on 

 its flanks large unmixed patches. A dwarf form of Sphucelaria cirrhosa is also 

 frequent, but, because of its small size, is apt to be overlooked. Though 

 a filamentous species, it is distinct from the others, being attached by a basal 

 disk, and not by rhizoids. In late summer, especially in the more sheltered 

 localities, Ehodochorton is much discoloured by the presence of cyanophyceous 

 epiphytes. Of these C'alothrix confervicola is the most common, being at times 

 so abundant as to create large black patches. Apkanotheca pallida is also 

 frequent. On the margins, where the association joins the Corallina- 

 Cladostephus vegetation, many other algae appear, and it is probable that the 

 borders of the two communities are in a continual state of change. 



Young plants of TJlva Lactuca are at times present in great quantity, 

 especially in spring, but this species is in no way a sand-binder, possessing 

 only a foliose thallus and a basal disk. In the same way we may dismiss 

 many other intruders, the Ehodochorton sward being, in fact, a general nursery 

 ground, the sporelings succeeding each other in regular sequence as the 

 seasons come round. 



With regard to distribution, the present community is probably very 

 widely spread in the British Isles. Rhodochorton florididum is one of the few 

 species that form extensive associations on the flat sandy shores of Sussex ; 

 and it has been found growing in the same way in Dorset and Devon. Harvey 

 states that at Kilkee (Co. Clare) " it often carpets large spaces on the rocks " ; 

 and Ealfs writes in a similar strain as to the plant at Land's End (in litt.). It 

 is also abundant on the shores of Belfast Lough. With regard to the Survey 

 area, the association is found at Portlea on Clare Island (rocks giving the 

 necessary shelter], and on a small scale in several other bays, where protection 

 is afforded by a heavy growth of Fucus. On the mainland, where for the most 

 part no special protection is required, it is very widely spread, probably coming 

 next to that of the Fucaceae in the amount of area covered. According to 

 Harvey the plant is washed ashore in quantity during autumn ; and the 

 hemispherical cushions are collected (under the name of " figs ") for use as 

 manure (Phyc. Brit.). 



