THE .^^AT{T^'E alg.e of arETf^-.sEi' 43 



witliin reach of the tide, Gladopliora spp. and Chafomorpha spp. 

 make their appearance. 



Half-tide pools are sometimes shallow, with sand and pehbles. 

 They contain such species as Asperococcvs Jiatulosus, J^olifsiplionia 

 ni(/rescens, Cladoplwra rnpcsfris, and Rhodomda auhjusca. Where 

 the l)ottom is rocky, l^adina pavonia, ILcdopitlnjs incur vtts, Poli/si- 

 phojiin elonc/ata, etc. grow luxuriantly; whilst Gelidium pulcliellum, 

 Grijfitlisia spp., CaUophyUis luciniata, Ldurencia spp., Lithotham- 

 uioii Lenormnndi, etc. are to ])e foiuid where there is sufficient shade. 



]5elow half tide the vegetation of rocky pools becomes varied and 

 abundant, including many sublittoral species. The edges of some 

 pools are lined with the beautiful and brittle LithophyUum lichenoides, 

 below which there is a heavy growth of Bifurcaria tuherculata or 

 Gystoseira spp. At the lower depth Nitophi/llum uucinatum or 

 GaUihUpharis Janceolata send up hooked shoots which climb among 

 the brown weeds. Other ])ools contain Bri/opsis pJumosa, Godium 

 tomcnfosum, Enferomorpha clathrafa, Gladopliora pellucida, G. dis- 

 fans, Biciijota dichotoma, Nitop)hi/llum punctatiim, N. ramosum, 

 N. Hillicp, Delesseria sanguinea, Gliylocladia ovata, etc. 



Corallines and Lithothamnions line the bottoms of most of these 

 pools with their pink and mauve incrustations : GoralUua officinalis, 

 G. squamafa, LHhopliyllum iucrustans, Litlioiliamnionpolymorplms 

 are the most conspicuous species. 



V. Composition of the Flora. 



The mixed character of the Marine Flora which flourishes on the 

 shores of Guernsey is doubtless owing to the geographical position of 

 the island, which is so situated (see p. 26) that it lies well within 

 the range of the Atlantic Flora. Guernsey is sufficiently near the 

 shores of the English Channel and the west coast of France to 

 participate also more or less in the type of vegetation fringing these 

 littorals ; this is composed very largely of a southern type of Floi-a, 

 along with certain types of Atlantic and cosmoix)litan marine 

 vegetation. 



NoETiiEEX Element. 



There is in Guernsey a well-marked element which belongs to the 

 vegetation of the North Atlantic, a Flora which extends to the 

 Norwegian Polar Sea ; many of the species, however, do not penetrate 

 farther north than Scotland or the Faeroes. Owing to the influence 

 of the Gulf Stream, which flows along the coasts of Norway and 

 round Cape North, the temperature there is much higher than in 

 other parts of the Polar Seas, so that the district characterised by 

 Kjellman as the "Norwegian Polar Sea" is not purely Arctic; the 

 Flora there is very closely allied to that of the North"^ Atlantic, and 

 is of varied composition with luxuriant littoral and tidal-pool vegeta- 

 tion. Brown alga? are dominant, though green alga3 are abundant, 

 with a fair number of i-ed species. Southwards, this Flora ceases 

 gradually along the Scotch and English coasts, the coasts of Spain 

 forming the southernmost limit of many species. 



