TUE ilAllINE ALGJJ OP GUERNSEY 39 



describes this species as " semi-marine, and iisuallj occurring along 

 the inner fringe of high tide mark between the orange lichens 

 and Verrucaria maura, and slightly overlapping these belts .... but 

 it is occasionally coextensive with that of V. maiira.'''' It is found 

 in the latter position along the shores of Guernsey in semi-exposed 

 conditions. 



L. pygmaa is conspicuous along the exposed districts of the 

 Guernsej^ coasts. It grows in patches over the upper parts of rocks, 

 more especially on stretches of boulder beaches where there are no 

 algJB except in pools ; this is contrary to the observations of Cotton, 

 who points out the bad effect of extreme exposure on this species. 

 According to Miss Knowles " L. i^yguKsa prefers rough surfaces and 

 steep rocks which face the breeze and around which the sea breaks. 

 Its range extends from the lowest limits of V. maura as far as low 

 neap tide, and the growth is best developed in the uj^per part of its 

 range among the Pelvetias and immediately below them." In the 

 district round Pleinmont the maximum development was at about 

 half-tide level. The growth of this lichen dwindles as shelter in- 

 creases, though it can still be traced all along the coast. Wherever 

 it occurs it affords a convenient site for the germination of sporelings 

 of F. spiralis, F. vesiculosus, and several other species. 



Zoriatioii of Boulders. 



It was interesting to observe how constantly tufts of Ascoj^hi/Ilioji 

 nodosum hung down from the lower parts of boulders in semi-exposed 

 localities. Above them grew a few scattered plants of F. spiralis 

 among the patches of Lichina pi/gmcea ; further up appeared more 

 Lichina, but the tops were bare. On the side of the rocks facing 

 the sea there was less growth than on the landward side. 



Bhodijmenia Zone. 



There is little or no Bhodi/menia palmata in the south of the 

 island ; on the other coasts it frequently forms wdde and extensive 

 zones from below half-tide level down to the sub-littoral. Its luxuri- 

 ance is for the most part unaffected by differences in climate, though 

 changes of form accord wnth certain changes in climatic conditions. 

 In the exposed district round Pleinmont, the plants of the littoral 

 region are sparse, and nestle in chinks of the rock or hang from 

 beneath over-arching boulders. They measure about 4 inches in 

 length ; the colour is dark red, and the stalks are stout and leathery 

 with strong attachment disks. The prevalent form is w^edge-shaped, 

 with numerous stalked ovate proliferations along the edges. The 

 plants of the sub-littoral are deeper in colour, thicker in texture, and 

 considerably longer, increasing even to 2 feet in length. The form in 

 this area varies from wedge to strap-shaped, with similar growths or 

 proliferations superposed in stages upon each other, and apparently of 

 greater significance than the leaflets of the var. marginifera. The 

 undergrowtlis are Chglocladia oralis, Laureiicia pinnafijida, and 

 Ilildenhrandtia sp. 



