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76 OLOF RUNETABLE 1. Upper limits (in m) of the commonest high-alpine vascular plants of Sweden.Lycksele Nordland Lule and Torne Lpm. Torne Lpm.Province ... Jamtland Lappmark (Norway) Pite Lpms. Lule Lpm. (Ke bnekaise) (Tornetrask)N. Syter- (Sulitelma) Tarfala- Nisson-Mountain ... He lags top pen Oxtind Jeknaffo Sarek tjakko tjarroAltitude of summit ... 1796 1792 1912 1700 2000 1830 1804Ranunculus glacialis 1780 1660 1900 1695 1900 1830 1760Poa laxa ssp. flexuosa 1790 1620 1900 1695Luzula arcuata s. lat. 1730 1650 1660 1690 1705 1740 1730Deschampsia alpina 1690 1530 1790 1680 1530 (ll 50) 1680Cardamine bellidifolia 1665 1500 1770 1640 1530 1590 1670Lycopodium selago 1750 1480 1550 1610 1650 1740 1680Salix herbacea 1740 1600 1660 1590 1705 1710 1480Cassiope hypnoides 1705 1500 1450 1435 1580 1500 1420Festuca vivipara 1730 1515 1450 1535 1530 1430Silene aca1tlis 1700 1550 1400 1525 1530 1240 1380Saxifraga oppositifolia 1700 1250 1535 1790 (ll40) 1680Carex Bigelowii 1695 1470 1550 1625Saxifraga foliolosa 1275 1475 1525 1510 1680Saxifraga cernua 1680 1250 1645 1395 ll80 1680T1·isetum spicatum 1680 1320 1280 1545 1530 1230V accinium vitis-idaea 1550 1320 1300 1400 1510 1370 1330As southern La pp land is poorly represented, the Norwegian high-alpine area of Mts. Oxtindene close to the border isincluded. The measurements from Mt. Oxtind and Mt. N. Sytertoppen were obtained by the present author. The othersare compiled froin KrLANDER (1955}, SELANDER (1950b), ALMEN & ALMEN (1959), and Du RrETZ (1925f). Some ·odd observationson other 'summits, e.g. of Ranunculus glacialis at still higher altitudes, ·have not been included.·Some other plants reaching high altitudes (above 1600 .m) are represented only on some •of the summit, being restrictedto particular types of habitats. Such plants are Phippsia algiaa, Saxifraga rivularis, S. caespitosa, Sibbaldia procumbens,Ranunculus pygmaeus, Oerastium arcticum.As seen in the table Ranunculus glacialis is by far the most common and widespread plant of the uppermost levels witha vascular flora. However in the high-alpine areas south of the Arctic Circle Poa laxa ssp. flexuosa is close to Ranunculusglacialis in importance. Poa laxa ssp. flexuosa has a southern distribution in Scandinavia, the mountains of Sulitelma beingits northernmost localities.Iabout 100 m higher. Beyond this altitude extendsthe high-alpine belt. At this level the climate issevere, the mean summer temperatures beinggenerally a few (possibly about five) degrees abovefreezing, and the freeze-thaw cycles occur in thesoil even during the summer. This causes an intensecongeliturbation in the soil, above all appearing asan up-freezing of boulders that accumulate in greatnumbers on the surface. In places where continuousboulder fields or late-thawing or perennial snow donot prevent higher plants from growing, singletufts of chiefly the following plants are found (seealso Table 1):Ranunculus glacialisCassiope hypnoidesSalix herbacea.d.cta Phytogeogr. Suec. 50Salix herbacea xpolarisLuzul arcuata (sens. lat.)\Poa laxa ssp. flexuosdP. alpinaP. arcticaDeschampsia alpinFestuca ovinTrisetum spicatumLycopodium selagoCardamine bellidifoliaSilene acaulisSaxifraga foliolosaS., other spp.Above all, the high-alpine vegetation is dominatedby lichens and mosses. Exposed boulders freefrom long remaining snow are covered by crustaceouslichens such as H aematomma veniosum andspecies of Rhizocarpon, Lecanora and Lecidea.Boulders later free from snow are overgrown bysmall, black tufts of mosses of the genus Andreaea.Apart from the few vascular plants, the solifluctionsoil has a thin coat of small mosses, hepaticsand lichens. Frequently seen are, e.g., Polytrichum