This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
The lowest limit of the arctic-alpine vegetation in Scotland is the 2000-ft. contour, but in Ireland and elsewhere it is not so high. It is above the tree limit in this country. Ling and Whortleberry, or moorland vegetation, disappears, and a sort of grassland, with dwarf vegetation, takes its place at higher levels, made up of Alchemilla, Grasses (often viviparous), Carex, Juncus, Luzula, Draba, Cerastium, Potentilla, Saxifraga, Sedum.
The types of plants are Scottish, or Highland at higher altitudes, the latter chiefly in Scotland. On Highland hills, e.g. on Ben Muic Dhui (4300 ft.) the following occur: Silene acaulis, Saxifraga stellaris, Salix her-bacea (typically arctic), Luzula spicata, L. ar-cuata, Carex rigida, Festuca ovina (viviparous form). Elsewhere these plants occur on alpine rocks in arctic and sub-arctic latitudes.
The altitudes attained by some of these arctic-alpine plants is illustrated by the following list of plants on high mountain-tops, many of which are rare or restricted to certain localities, viz.: Draba rupestris (3000-3980 ft.), Saxifraga cernua (3800 ft.), S. rivularis (3500-3900 ft.), Arenaria rubella (2700-3800 ft.), Sagina nivalis (3100-3900 ft.), Astragalus alpinus, Oxytropis campestris, Erigeron alpinum (2500-3500ft.), Gnaphalium norvegicum, Menzesia coerulea (2350-2460 ft.), Gentiana nivalis (2400-3450 ft.), Myosotis pyrenaica (2400-3450 ft.), Veronica fruticans (1200-3600 ft.), Salix arbuscula, S. lanata (dwarf willows), Juncus biglumis, Carex alpina, C. rupestris, C. atrofusca (2600 ft.) A number of lowland types also occur at high altitudes (see ante). In this group of arctic plants we see the influence of altitude and insolation in a marked degree.