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112 H. PETER HALLBERG AND REINHOLD IV ARSSONThus Ledum palustre has only a few stations in theeasternmost parts.Subcontinental plants (STERNER 1922) are numerous,particularly forest plants and verge plants,e.g. Acer platanoides and Ranunculus polyanthemus,while eucontinental plants are lacking. The northernspecies are not so few, though fairly sparse.Selaginella selaginoides, Alchemilla alpina, Sedumrosea (LID & ZACHAU 1929), and Rhytidium rugosum(HALLBERG 1959) chiefly occur near the coast.Approximately 50 phanerogams reach their Scandinaviannorthern limit in BohusHin (cf. STERNER1945, p. 63), while many others stop just south ofBohusHin, among them the sand plants Arnoserisminima and Corynephorus canescens, and theGenista species of the heaths.CULTURAL INFLUENCE.-In the coastland ofBohusHin, scrub and wood occur in small clustersin an otherwise open landscape. This is attributedmainly to the cultivation which has long been inprocess in the coastal region (cf. M. FRIES 1958 b).In the regions near the .shore the woods wereearly cleared away to give place to meadow andpasture. Further inland the woods were worked up,and at times, according to hearsay, much of thetimber was bought by Scots and Dutch (KALM1746, pp. 117 and 153). The large shoals of herringappearing periodically along the west coast createda great need of timber for piers, boats, and buildings,as well as of fuel especially for trying out oil(DALEN 1941, LINDNER 1935). During these profitableperiods of herring fishing the brush vegetationincreased, as the pressure from agriculture andgrazing was temporarily reduced. In the intervals,fields were broken up almost everywhere, even inplaces that now look as if they had been heatherheath or other pasture-land for very long. In themiddle of the 19th century the west coast regionwas the most deficient in woody plants, but scatteredshrubs occurred here and there. However,the brush was entirely exterminated for a distanceof 2-3 km around the fishing villages.The best land, i.e. the soils suitable for foliiferousforest, was used for cultivation. The forest growingon the rocky ground of the BohusUin coastland,with its smali quantity of loose deposits, probably.Acta Phytogeog1·. Suec. 50never was particularly dense or high (cf. above).The open rock ground has, in all likelihood, alwaysbeen extensive, and this has increased greatlyowing to neglect. The fields were often manuredwith the humus from the rocky ground. Largeflocks of sheep grazed there and, in mild winters,probably stayed out all the year round. The intensegrazing produced a vegetation dominated by grassland,resembling that covering parts of Great Britainin our time. Nardus stricta may possibly havebeen dominant on wet sites, while Agrostis tenuis,Deschampsia flexuosa and Festuca ovina were themost frequent in dry places. When grazing decreasedin intensity, Call una immigrated and formedextensive heaths. In order to improve the pasturage,the. heath was burnt at regular intervals. Theorganic material deposited largely by the regularshedding of shoots of Calluna (HoLMBOE 1909) wasconsumed by the fire together with the vegetation.When the wind was strong, the ashes were blownaway, along with the fine inorganic material accumulatedby - disintegration. The natural prerequisitesof forest growth on rocky grounds havebeen severely restricted by these conditions.In BohusHin of today (HAGBEG & TERSMEDEN1954), cultivated land (incl. roads etc.) occupies32 % of the land acreage, productive woodland33 %, and unproductive land 35 % (rocky hillsapproximately 30 %). In the bare skerry regionand the deciduous wood region (see below), thefarmland constitutes about 5 to 15 %, the woodland10 to 20 %, and the unproductive land morethan 50 % (ATLAS OVER SvERIGE, maps 67-68,1953).VEGETATIONAL REGIONS.-Bohuslan can be dividedinto three regions, according to the compositionof the ligneous vegetation. From west to east,they are as follows: the bare skerry region withisolated thickets and shrubby woods (Du RrETZ1925c and e, 1933b; IVARSSON 1962, p. 7), thedeciduous wood region (comprised in the southerndeciduous forest region, see "Forest regions"), andthe coniferous forest region (comprised in thesouthern coniferous forest region). The last-mentionedregion is delimited by the western border ofthe wild spruce forest, which has been considered