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102 VILHELM GILLNERing cease Alnus glutinosa soon makes its appearance, and the vegetation thus merges into an alderwoodalliance Alnion glutinosae. In northern Bohus­Hin this frequently forms the inland border of saltmarshes influenced by freshwater.Grazing and haymaking keep back Phragmitescommunis, which would otherwise be widespreadin the subassociation of Juncetum gerardi influencedby freshwater and elsewhere. On the whole itseems true to say that the vegetation of marshessubject to freshwater seepage are more affectedby the activities of man than the truly saline onesdescribed at the beginning of this section.Salt marshes on the OresundExtensive salt marshes are found in southernSweden where the coast of Skane overlooks theOresund. Their vegetation has been described indetail by DAHLBEOK (1945).The variations in the water level are about thesame in the Oresund as on the West Coast, but thetides are even more insignificant. The salinity ofthe surface water is considerably lower than on theWest Coast and has its highest values during thewinter half year. Thus in November and Februarythe salinity off Skanor was 10%0, in May and August8%0• Further north in the sound it increasesnoticeably, however. Concerning salinity the Oresundforms an interesting transition between theBaltic Sea and the Kattegat.When describing the vegetation DAHLBEOKdistinguished the communities on a morphologicalphysiognomicbasis. This somewhat complicates acomparison with my own West Coast materialclassified on floristic. grounds.In the hydrolittoral we once again find Scirpetummaritimi, corresponding to DAHLBEOK's Scirpusmaritimus, Se. Tabernaemontani and Phragmitescommunis "isocions". Heavy grazing has been fatalto it in many places, however, and it only occurson parts of the shoreline sheltered from grazing.Significantly enough there is no equivalent of Salicornietumstrictae, so characteristic of the WestCoast and North Sea coast, where the water ismuch more salty.The lower geolittoral is often the home of Puccinellietummaritimae in its typical form. However,where the influence of freshwater is felt it is presentin a special subassociation with Agrostis stolonifera,a transition to communities with Eleocharis uniglumis and Agrostis stolonifera on less saline substrates.As we have seen similar conditions prevail on theSwedish West Coast. A different subassociation ofPuccinellietum maritimae occurs on strongly salinesoil. Here it is found with Salicornia europaea,Suaeda maritima, Spergula marginata, H alimionepedunculata and Parapholis strigosa. The last-named,also called Lepturus filiformis, is easily overlooked.· In the central and upper geolittoral large areasare covered by various forms of Juncetum Gerardi.(In DAHLBEOK this association corresponds to suchisocions as those of Juncus Gerardi, Glaux maritima,Plantago maritima and Festuca rubra.) A few southern species, rarer at. the West Coast, are noted,among them Oarex extenso/ (recently discovered ina locality at the West Coast), Oarex distans andLotus tenuis.A rather prominent southerly association is Artemisietummaritimae. To it belongs the Staticelimonium ( =Limonium vulgare) isocion distinguished by DAHLBEOK (1945, pp. 76-78), which isamong the most halophytic vegetation of the saltmarsh. The typical Artemisietum maritimae (cf.the Artemisia maritima isocion in DAHLBEOK)grows in the central and upper geolittoral and, asalways, thrives on a slight addition of drift. DAHL­BEOK also points out that it forms long belts parallelto the shoreline. As grazing animals do not consumeArtemisia maritima and only exceptionallyLimonium vulgare, Artemisietum maritimae benefitsby their presence on the salt marsh.As on the West Coast a Sagino maritimae­Cochlearietum danicae occurs on open patches highup on the marsh. Plantago coronopus is common.Bupleurum tenuissimum is also conspicuous.An association favoured by drift is Potentillo­Festucetum arundinaceae, with Festuca arundinaceaas dominating species and Potentilla anserinaand Rumex crispus as other characteristic members(cf. the Festuca arundinacea isocion in DAHLBEOK).The association belongs to an alliance Agropyro­Rumicion very characteristic of brackish marsheson the Baltic but hardly found in its typical format the West Coast.Acta Phytogeog1·. Suec. 50