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The southern mires 151Fig. 2. Wooded bog vegetationwith Pinus silvestr:s, Ledum palust?·e(flowering), Vaccinium ttliginosumand Eriophorum vaginatum.Sphagnum parvijolium dominantin the bottom layer. Asmall mire in Central Smi'tland,south of Vaxjo. June 5, 1961.Photo N. Malmer.large mire areas. In the west it is absent or confinedto the most well-drained parts, usually to stronglysloping marginal parts of concentrically domedbogs. Pinus silvestris is the only tree of importance,except in southern and middle Skane and the coastalareas of southern Halland where it is replaced byBetula pubescens. Above all Eriophorum vaginatumbut also Calluna vulgaris, Empetrum nigrum andRubus chamaemorus are always important. Lowshrubs such as Vaccinium uliginosum, Ledum palustre(only in the eastern parts) and Betula nana(only locally in the uplands) often form a physiognomicallyvery characteristic element. Sphagnumparvifolium together vvith S. magellanicum, S. nemoreum,Aulacomnium palustre, forest mosses (Dicranumspp., Hylocomium splendens and PleuroziumSchreberi), liverworts and several Oladonia spp.characterize the bottom layer. - Similar types ofwooded fen vegetation (in which exclusive fenplants as Oarex echinata, 0. pauciflora and Eriophorumangustifolium occur in addition) are commonin depressions in forested areas and along theborder between mires and the mineral soil.The typical woodless bog vegetation co:p.sists of auniformly repeated mosaic of hollow and hummockcommunities. In the wettest parts of the hollowsSphagnum cuspidatum is the most important species,often together with or replaced by Zygogoniumericetorum and other algae (cf. Du RmTz 1949a,1950a, b and c, 1954b; FETZMANN 1961; FLENS­BURG's paper in this book). In south-western Swedenit is often associated with Drosera intermediaand Rhynchospora alba. In the large wet hollowsand hollow-pools on the bogs in Svealand andnorthern Gotaland Oarex limosa and Scheuchzeriapalustris occur. Typical hollow-pools are not foundin southern Gotaland. The pH of the open surfacewater is about 3.7-4.0 in summer. It is somewhathigher in winter, but it does not vary betweendifferent parts of South Sweden (MALMER l962a, b).The upper, less wet parts of the hollows differfrom the adjacent hummocks in the absence ofCall una (except small shoots). Eriophortm vaginatumand, chiefly in the west, Trichophorum caespitosumssp. austriacum dominate the more sparsefield layer. Always present are Andromeda polifolia,V accinium oxycoccos and Drosera rotundifolia whichare shared with the hummock vegetation. Similaroccurrence, but only within a geographically restrictedarea, have Erica tetralix (only in the westernActa Phytogeogr. Suec. 50