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222 SVEN RUNEconiferous forests, and of the mires and other wetlands, a limited number have a wide distribution,and the principal part of the flora consists of speciesevenly dispersed over the whole of wooded Lappland.This gives a uniform character to the woodland,but the uniformity is far from complete. Acloser study shows considerable regional differenceswithin the Lappish woodland, between its southernand northern parts and especially between its easternand western parts. When going from the coastthrough the woodland up to the mountains oneobserves much greater changes as to vegetation andflora than if one travels a distance twice as longbut in the south-north direction. Altitude meansmore in Lappland than latitude. The successivedepression of the spring, summer . and autumntemperatures in a westerly direction is reflected inthe distribution of certain thermophilous species· within the woodland.The southern elementMany species that have their principal distributionin Sweden south of the natural boundary ofNorth Sweden (see the articles on "Forest regions"and "The Borderland") grow far up in thecoastal regions along the Gulf of Bothnia, presumablybecause they are favoured by warm summersand relatively long autumns. As a rule they ceaserapidly up country, but many of them reach fromtheir Bothnian stations up to the eastern part ofthe Lappish woodland. Thus Viburnum opulus,Myrica gale and Salix repens, for example, growin a few stations mainly in the south-east part ofLappland. Others have a wider distribution, andare found in fairly numerous but scattered localitieschiefly within the eastern part of the woodland:Pteridium aquilinumCalamagrostis epigeiosS cirpus lacustrisHammarbya paludosaCicuta virosaPeucedanum palustrePolygonum amphibiumIn the woodland Rhamnus frangula occurs in seatteredstations along brooks and in rich fens. Itreaches the Caledonian border in the south ofLappland while its northernmost stations are foundin the central woodland of Lule Lappmark.The following hydrophytes are restricted to thesouth of Lappland:Lobelia dortmannaSagittaria sagittifoliaSparganium glomeratumSparganium FriesiiPotamogeton filiformis, Juncus balticus and Elymusarenarius, which are common on the shoresof the Gulf of Bothnia have also a few inland stations,and (though not southern) belong to the rarespecies of the Lappish woodland flora.With a continuous distribution centered on theshores of the lakes and rivers in the valleys thefollowing species reach deep into the central woodland,some of them with occasional localities ateven higher elevations:Alisma plantago-aquaticaPhalaris arundinaceaEleocharis palustrisConvallaria maialisLysimachia thyrsi floraM yosotis caespitosa ssp.lax aS cutellaria galericulataLysimachia and Scutellaria have wider areas thanthe others and .are also found between the mainvalleys. Along the river Lilla Lule alv the speciesmentioned above have their weste.rn limits nearlycoincident. As far as known this is valid for thegreater part of the woodland with certain exceptions.For the middle Pite river, notes are given byWISTRAND & JrM LuNDQVIST (1964). Myosotis caespitosassp. laxa is known in Pite Lappmark onlyin a few stations, some of which are situated nearthe Caledonian border. Sagina nodosa, Prunellavulgaris and Garex Oederi (in a wide sense) arealmost completely bound to the banks of the bigwatercourses, where these species are common. Insome parts they ascend as far as the subalpine belt.These watercourses have their sources in themountains and have a large amplitude in waterlevel, with a prolonged high water in early summer.The species mentioned above are particularlyfavoured by the special conditions prevailing in abroad inundation zone. In Lule Lappmark noneof these species has been observed along those lakesand rivers which drain only wooded areas and havea smaller amplitude in water level.Phytogeographically interesting stations of adifferent, but also thermophilous flora are foundin the numerous south-facing precipices and talusslopes (screes) in the western part of the woodland.Near the Caledonian border such localities, whenentered on a map, form a row like the pearls of a.Acta Phytogeogr. Suec. 50