Knowli':s — The Maritime and Marine Lichens of Hototh. 107 



are botli widespread along the Howth shores, Z. pygmaea preferring rough 

 surfaces and sleep rocks which face tlie breeze and around whicli the sea 

 breaks. Its range extends from the lowest limits of Verrucaria inaura as far 

 as low neap-tide and the growth is best developed in the upper part of its 

 range among the Pelvetias and immediately below them. It is most common on 

 the rough quartzites and grits, but it also occurs on the slates and sometimes 

 on the pure quartz bands. Lichina confinis grows usually above V. maura in 

 sheltered places ; on flat shores its range is, however, frequently coextensive 

 with that of V. maura. 



Where Lichina confinis is found growing high on the cliffs beyond its 

 natural habitat, in situations where it only receives occasional showers of 

 spray and is mainly dependent on rain for moisture, the fronds are seldom 

 fertile. The greatest height above sea-level at which it was noticed on the 

 Howth coasts was that quoted from Drumleck Point, viz., 50 feet. On the 

 west coast of Ireland, however, L. confinis often rises to very much greater 

 heights. I have gathered it on the tops of the cliils of High Island, off 

 the coast of Galway, 200 feet above sea-level. 



The zonal distribution of the Lichinas on the sea-shore has long been 

 known to botanists. Sir William Hooker and Nylander were among the 

 first to draw attention to it. Nylander, in his account of the Lichens of 

 Pornic (20), describes Lichina confinis, Verrucaria maura, and L. pygmaea as 

 forming three distinct zones, L. confinis along the upper part and L. pygmaea 

 along the lower part of tlie beach, with V. maura in an intermediate position ; 

 and he says that all three species are wholly submerged by the incoming tide. 

 Weddell describes a similar arrangement on the coast of I'lle d'Yeu, but 

 points out that during low tides L. confinis is often not submerged at all. 

 On the Howth coasts this is also the case. A. D. Cotton's account of the 

 Lichina communities in the Clare Island Survey area shows that the same 

 zonal distribution exists on the west coast of Ireland. The Lichina vegeta- 

 tion of the Howth coasts is very similar. The growth on the low sheltered 

 shores of Broad Strand resembles very closely that described by Mr. Cotton 

 for the coasts of Clew Bay and Achill Sound. 



(4) The Verrucaria maura Belt. 



This belt normally occupies the part of the shore between high neap- and 

 high spring-tide marks. It lies chiefly above Peketia caiianiculatus, but 

 where this seaweed is ahaent Lichina pygmaea frequently determines the lower 

 boundary. On flat shores V. maura sometimes seems to occur throughout the 

 whole range of Pelvetia ; but, when this is so, examination always shows that 

 V. maura is found only on the rather higher parts of the rocks, where it is 



