36 the maei>'e alg^ of gueeysey 



Upper Littokal. 

 Verni^caria Zone. 



Verrucaria maiira grows over the dr}^ jagged rocks, giving them 

 a mottled appearance and forming a well-marked band a short 

 distance above the Helvetia zone. This extends romid the island 

 independent of aspect, but is interrupted here and there by the 

 encroachment of sea-wall or dykes, or the absence of suitable rocks. 

 V. mucosa occurs in infrequent patches, often dry and ex}X>sed to 

 sunshine for a considerable period of time ; it extends from the limit 

 of V. maura down to about half tide, where it forms dark green, 

 almost black greasy stains among Ascophyllum nodosum. Both of 

 these Yen'ucarias have been fully dealt with by Knowles and Cotton. 



Pelvefia, which occupies the upper reaches of the littoral, is most 

 sensitive to exposure, and its line is very varied in width. It is 

 scantily developed in the exposed districts, growing onl}^ on rocks 

 covered at high tide, and disappears altogether w^ith extreme exposure. 

 Where the projection of a reef screens a portion of the shore, the 

 Pelvetia band immediately widens, to the extent of several yards, 

 according to the sloj^e of the shore. In summer the orange-coloured 

 receptacles lend a distinct note to the surroundings. Along the north 

 arm of Kocquaine Bay, Lihou Causewa}^ and L'Eree Bay, where the 

 conditions are semi-exposed, there are great patches about 15 feet in 

 depth. Again, with moderate shelter, and where the shore is very 

 flat, the zone w^idens out enormousl}^, as at Port Grat, and Grrand 

 Havre, a land-locked bay ; but at no point is there much Pelvetia 

 above high-water mark. In several localities of moderate shelter 

 there is only a scanty growth on account of the steepness of the rocks ; 

 where a wall and roadway skirt the shore, the Pelvetia band 

 disappears for long distances. 



Mivularia and Calotlirix Zone. 



About high-water mark, but just below the V. maura belt, a line 

 of Rivularia and of Calotlirix occurs to a depth of 2 or 3 feet 

 in dots and patches, and corresponds to the Pivularia and Calotlirix 

 association described by other workers. It consists of Calotlirix 

 Crustacea, C. scopulorum, C. confervicola, C. hydnoides, Lijngliya 

 (Sstuarii, L. majuscula, Schizosiplton JVarrenice, Isactis plaiia. 



The zone is more apparent in exposed and semi-exposed regions ; it 

 decreases with moderate slielter, and with the exception of a wide 

 scattering of Pivularia hullata almost vanishes from sheltered 

 positions. 



Pluteromorplia Zone. 



The Enteromorpha Zone is very broad and consists for the most 

 part of -E". intestinalis. It extends from the Piviilaria and Calo- 

 tlirix line down through the other belts to low- water mark, often as an 

 ■undergrowth. In exposed regions the development is poor, forming 

 only a scanty growth on low rocks, or in pools. With shelter it 

 becomes more noticeable and is mixed with Cladopliora rupestris, 

 Chcetomorplia spp., etc. Great luxuriance is attained with increased 

 shelter. 



