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148 EDV ARD VON KRUSENSTJERNASENSTJERNA 1945, p. 74), which is a more demandingequivalent to Plagiothecion and a photophobousequivalent to Grimmion commutatae, occurs eitheron steep cliffs in forest outskirts or on bouldersin shady, usually deciduous woods and parks.A mblystegium serpensBrachythecium populeumHypnum cupressijormeLeskeella nervosaOrthotrichum anomalumGrimmia H artmaniiHypnum cupressijormeM nium cuspidatumParaleucobryum longifoliumPlagiochila asplenioidesTortula ruralisOn small boulders in grovesand parks (v. KRu­SENSTJERNA 1945, p. 76)On boulders of mediumsize, where the low carpetsof Leskeella, if present,soon become overgrown.M. cuspidatumis the most characteristicspeciesPlacynthium nigrumProtoblastenia rupestrisBlastenia leucoraeaCetraria islandicaOladonia furcataa. symphycarpiaFulgensia bracteataLecanora lentigeraLecidea decipiensToninia spp.Olevea hyalinaDitrichum flexicauleEucladium aeruginosumRhacomitrium canescensSchistidium apoca'rpumTortella inclinataT. rigens. T. tortuosaOther types of lichens(ALBERTSON op. c., p. 46)Mosses, often formingdark cushionsA nomodon attenuatusA ntitrichia curtipendulaBarbilophozia barbatalsothecium myurumThese four species havebeen grouped because oftheir tendency to overgrowsmaller mosses andbecome dominant (Barbilophozialess. so)In the Tortellion of the Stockholm archipelagoa more or less important role is also played byCtenidium molluscU'nt, Barbula convoluta, Orthotrichumcupulatum and (sometimes) Tortella fragilis,whereas T. inclinata is absent.A few more unions were described (v. KRUSEN­STJERNA op.c.) but attention should also be paid toSJOGREN (1964), who has carried out careful investigationsinto related communities named GrimmienHartmanii in deciduous forests mainly onbland.Communities on Archaean or Palaeozoic limestone. THE TORTELLA FEDERATION (TORTELLION).­This federation contains basiphilous (possibly calciphilous)and photophilous societies and unions, inSweden mainly investigated by ALBERTSON (1941 a,1942a, 1946a, 1950), in certain respects also byDu RIETZ (1916, 1925 b, NANNFELDT & Du RIETZ1945) and BENGT PETTERSSON (1950, 1958). The federationis most typically developed on Gotland andbland and in the calcareous parts of Vastergotland(ALBERTSON 1946a), but considerable areas in theStockholm archipelago, too, have these communitieson calcareous rock.Lecanora calcareaL. contortaV errucaria nigrescensImportant crustaceouslichens (ALBERTSONl946a, p. 34)THE ENCALYPTA STREPTOCARPA FEDERATION(ENCALYPTION).-Here belong communites formedby more or less photophobous and calcicolous orcalcicline species such as Encalypta streptocarpa,N eckera crispa, H omalothecium sericeum, Barbulafallax, Eucladium recurvirostre. Tortella tortuosaoften occurs in this community too, but no otherspecies of this genus .Barbula cylindricaOampylium chrysophyllumDistichium montanumSeligeria pusillaTimmia austriacaOther species found togetherwith EncalyptastreptocarpaThis federation has been little studied in Sweden.ALBERTSON (l946a, p. 35) combined it with Aspleniumruta-muraria to an alliance ("Asplenion-Encalyption").A related but largely different epilithic federation,Schistidio-Anomodontion, growing in deciduouswoods on either calcareous boulders or siliciousboulders influenced by calcareous dust, was describedmainly from bland by SJOGREN (1964).Acta Phytogeog1·. Suec. 50