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264 OLA V GJ lEREVOLLFig. 4. Athyrium alpestre on a well-watered slope, withmeadowlike vegetation (transitional between Cryptogrammo-Athyrion alpestris and Ranunculo-Anthoxanthion).Low-alpine region of Mt. Laktatjakko, TorneLappmark. Aug. 5, 1950. Photo Gunnel Sji:irs.Communities poor in calciphiles but rich in hygrophiles(meadow series)RANUNCULO-ANTHOXANTHION.-The late snowfreemeadow communities corresponding to Deschampsio-Anthoxanthionare characterized by anumber of hygrophilous species, e.g. Alchemillaglomerulans, Ranunculus acris, Rumex acetosa,Sibbaldia procumbens, Taraxacum croceum, andViola biflora. The most important grass is Anthoxanthumodoratum (alliance Ranunculo-Anthoxanthion).The alliance requires a good supply of moisturefrom moving water, normally supplied as thawwater from above-lying snow-fields. It is muchmore heterogeneous than Deschampsio-Anthoxanthion.Because of its abundance Ranunculus acrisis very conspicuous. This community is the unpretentiousflower garden of the mountain builtup by acid rocks.Compared to Deschampsio -Anthoxanthion, thisvegetation shows a great difference also in thebottom layer, which is characterized by hygrophilousmosses ( Brachytheciurn, Philonotis, W ebera)and hepatics (Barbilophozia, Lophozia).STELLARI-0XYRION.-When the snow melts solate that the herbs characteristic of Ranunculo­Anthoxanthion and the majority of grasses are nolonger able to compete, they are replaced in thefirst instance by Oxy'ria digyna, Saxifraga stellaris,Oarex Lachenalii etc., and locally by 0. rufina,Deschampsia alpina and other hygrophiles (allianceStellari-Oxyrion). As to time of exposure, thisalliance is equivalent to Herbaceon.These two alliances are frequently met with. Inareas with abundant occurrence of Salix herbaceacommunities, Stellari- Oxyrion alternates withthem in irrigated places. The vascular plantsusually grow scattered, none of them reaching anyhigh degree of cover. Due to erosion the groundis stony. The bottom layer is accordingly interruptedand poorly developed. An exception isformed by the communities predominated by Oarexrufina, occurring in the most oceanic parts of thenorthern mountains. This low sedge is always foundon level ground with stagnant water and with awell-developed moss carpet ( Oalliergon, Drepanocladus,A nthelia).PoLYTRICHION NORVEGICI.Where the snowmelts so late that no phanerogams are able toexist, extensive areas may be covered by mossesand liverworts (alliance Polytrichion norvegici).In favourable years the growth period may befairly long (over a month or so), but normally itis short, and in extreme years the vegetation mayeven fail to appear from the snow, thus leaving thebryophytes to exist for two or even more yearswithout a period of exposure to daylight. Becauseof the late exposure a rich supply of water willnormally be present. Thus the division into aseason-hygrophilous heath series and a hygrophilousmeadow series can scarcely be applied tothese very late exposed snow-beds devoid ofphanerogams.The predominant species are Polytrichum norvegicum,Webera commutata, Dicranum Starkei, Oonostomumtetragonum, Drepanocladus purpurascens,A nthelia juratzkana, Gymnomitriurn varians, Andreaeaspp., and Solorina crocea.The alliance is of fairly frequent occurrence,Acta Phytogeogr. Suec. 50