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The Borderland 175Fig. 4. The Nittenmossen, uplandof southernmost Dalarna, is anexample of a concentricaHy domedbog above the limit for generaloccurrence. This is due to specialtopography, as the bog is almostsurrounded by lakes and streams.The bog in the foreground slopesunilaterally, as is normal for thisregion. Air photo G. Lundqvist1948. From Berg och Jord iSverige.\former type is always wooded (by pine) and thelatter either entirely wooded or wooded only in itsbroad marginal parts, whereas the wet central partis open. An upper limit for raised bogs was determinedby GRANLUND (1932) who paid attention toits near coincidence with the topographic boundarymentioned in the first part of this paper. Becausehe did not define "raised bog" as domed bog exclusively,there are minor inconsistencies in GRAN­LUND's boundary, and further research has alsorevealed odd examples of domed bog above and tothe north of this boundary. The important thing isnot the vanishing of the domed bog but the shift,close to the topographic boundary, to prevalenceof bogs that are unilaterally sloping or developedeccentrically in other ways (G. LUNDQVIST, e.g.1930, 1933, 1951a; SJORS 1948a, FRANSSON, inprep.). At higher altitude, the minerotrophic, chieflysoligenous fens become prevailing at the expenseof ombrotrophic bog. These differences are regardedas dependent on humidity perhaps more than ontemperature, and also on landforms and types ofQuaternary deposits, and their variable permeabilityto water.Some physiognomic types of peat-forming vegetationare frequent in and above the border zone'but rare below it. This is true of some caespitose oralmost lawn-like communities growing hi minerotrophic,largely soligenous (sloping) sites, usuallywith Trichophorum caespitosum prevailing and frequentlywith M olinia coerulea as another domiriant.Also mud-bottom vegetation is much more frequent,in this case both in ombrotrophic an:d minerotrophicsites. In the latter, it chiefly occurs inso-called £larks, a feature not found south of theborder except locally on the isolated upland ofGlaskogen in SW Varmland (FRANSSON 1958).Many of the other characteristic features ofnorthern mires are frequently found in the miresof the humid parts of south-western Sweden, e.g.soligenous fens, eccentrically developed bogs andlawn communities of poor fens.As to composition by species, intermediate fencommunities in the sense of SJORS (1952) occur inthe ·upper parts of the border zone, and to a greaterextent farther north; this type of vegetation is notknown to occur at all south of the borderland, andcontains many species that have a more or lessnorthern distribution. In the section on "NorthernMires" of this book, a short description is found ofthe kinds of mire vegetation that are typical of thecountry continuing north, from the borderland on.Acta Phytogeogr. Suec. 50