Clare Island Survey — Marine Algae. 15 27 



deserves mention in the present report. The second species, L. confinis, is 

 scarcely littoral, being confined to rocks just, above high-water line, but its 

 growth may be suitably described together with that of L. pygmaea. The 

 zones formed by these two species at times approach one another, but they 

 never overlap. Both occur on sheltered as well as on exposed coasts, though 

 for L, pygmaea rocks or boulders are essential. With the exception of Joubin 

 ('09), algologists have not dealt with this vegetation, though Nylander, as long 

 ago as 1861, drew attention to the belts of Lichina on the sea-shore. 



(a). L. pygmaea, the larger and more conspicuous species, forms circular 

 patches which vary from a few inches to a foot in diameter. It usually 

 commences immediately below Pelvetia, and extends downwards through the 

 F. spiralis belt to F. vesiculosiis, or to within a few feet of low-water. In 

 certain localities it extends well up into the Pelvetia band; but it never occurs 

 above it. The maximum development usually takes place in the upper part 

 of the zone, where the plant often forms a very conspicuous black band on 

 the vertical faces of rocks or boulders capped with F. spiralis. It undoubtedly 

 favours sloping or vertical surfaces; but it also occurs on those that are 

 horizontal. Though frequent on smooth boulders, it prefers rough or eroded 

 rocks, and is abundant on barnacles. Unlike L. confinis, the present species 

 can only stand a certain amount of drying. In the lower part of the associa- 

 tion it occurs fully open to the sun; but in the uppermost levels it is usually 

 found in chinks and pockets which retain moisture, or on rocks with a shady 

 aspect. In calm weather, during neap-tides, the Pelvetia zone may be left 

 entirely dry for several consecutive days ; and any growth of L. pygmaea that 

 reaches this level is occasionally subjected to like conditions. 



On the exposed and semi-exposed shores of Clare Island and the mainland 

 L. pygmaea is abundant, but where the exposure is excessive it does not 

 appear to flourish. On the large blocks and boulders to the north of Portlea 

 it is one of the few macroscopic plants which form a definite association; and 

 in such localities, where Puci are absent, the lichens form a useful means of 

 determining tidal levels. A very luxuriant vegetation of Verrucaria spp. 

 covers the boulders of this beach almost from top to bottom (p. 20). 



During the summer (July-Sept.), a fine growth of Rivularia bullata is 

 frequently found epiphytically on L. pygmaea. In 1911 it was unusually 

 abundant, being noted in August in all the exposed parts of the mainland 

 and Clare Island. B. hullata is not confined to the Lichina patches, but 

 also occurs on bare rock. It sets in about half-tide level, and continues to 

 low-water mark. 



1. . The second species, L. confinis, has fronds barely 3 mm. long, and the 

 individual patches are 2-4 cm. in diameter ; being black in colour it is very 



D2 



