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also on a substratum lacking shells, being evidentlymanifestations of "der okologische Vikarismuszwischen Meeressalz und Kalkgestein" (Du RIETZ1932 b, p. 100; cf. p. 82). On deeper soil Sedo­Tortelletum comes into contact with Tortulo­Phleetum and Helictotrichetum pratensis, on wetsoil with Cariceto-Ctenidietum (see below).Vegetation of coastal Bohusliin 119HELICTOTRICHETUM.-The Helictotrichetum pratensis,often grazed by sheep, has a large distributionin the northern archipelago region on thicksoils containing shell deposits. However, as grazingis now ceasing its distribution is diminishing. Thelocal type constitutes a geographical variant, lessdiversified in species composition, of the Helictotrichetum( =Arrhenatheretum, Avenetum) pratensisdescribed from different parts of Sweden(see, e.g., ALBERTSON 1946a, 0. ANDERSSON 1950a).According to ALBERTSON, "Avenetum" is only anorthern facies of the Bromion alliance ( 1946 a,p. 37). Common dominants in BohusHin are Anthyllisvulneraria, Arrhenatherum (Helictotrichon)pratense, Filipendula vulgaris and Fragaria viridis.There are several subassociations that are relatedto Tortulo-Phleetum, Cariceto-Ctenidietum (seebelow) and Nardetalia communities (see above).At weak grazing the Helictotrichetum changes ina direction towards pre-stages of the Geranietumsanguinei (see below). Similar transitional communitiesmay develop on mown ground. Throughthe neglect of grazing, they have at present a largedistribution. Contrary to Helictotrichetum pratensis,they contain, among many others, Arrhenatherumelatius, Centaurea scabiosa, Geranium sanguineumand Ranunculus polyanthemus, but lack suchspecies as Astragalus glycyphyllus, Campanulatrachelium, Origanum vulgare and Satureja vulgaris,which characterize the Geranietum.GERANIETUM.-The Geranietum sanguinei is amarginal community, which has several times beendescribed from South Scandinavia (cf. lv.ARSSON1962, p. 103). It may be placed in the allianceTrifolion medii of MuLLER (1962, p. 121). In NorthBohuslan it is found mainly differentiated intothree subassociations, viz. one with Filipendulaulmaria (on wet soil), one "typicum" subass. andone with Deschampsia flexuosa (on dry soil). TheFig. 4. A narrow valley almost filled by a shell deposit.Zonation: Tussilago farfara on clayey field; Geranietumsanguinei with bright flowers of lnula salicina; Prunetumspinosae; aspenwood growing between boulders at thefoot of the rocky hill, with Quercus robur and petmea,Acr platanoides, Fraxinus excelsior, Ulmus glabt·a, etc.Island Hamburgon, Kville, northern Bohuslan. July 22,1960. Photo H. P. Hallberg.association is mostly found on the borders ofPrunetum thickets (see below) or woods of Corylus,Fraxinus, Quercus and Ulmus (cf. lvARSSON 1962,pp. 103, 109), along fences, on slopes, etc., havingas a rule a southern exposure. It is often a Saumcommunity (Ti.TXEN 1952), i.e. a narrow ecotone.PASTURE-LAND AND WOODS.-Most of the shellbanks in the coastal area (landwards from thearchipelago) have been utilized for the grazing ofcattle and horses, but are nowadays often plantedwith Picea abies. The vegetation of the dry pasturescan be comprised preliminarily in the singleAlchemilla glaucescens - A nthyllis vulneraria association.Apart from Anthyllis, Plantago media is oftendominant, and Camptothecium lutescens in the bottomlayer. The association lacks Arrhenatherumpratense, Filipendula vulgaris, Fragaria viridis andother exclusive species of Helictotrichetum pra-Acta Phytogeogr. Suec. 50