MOORLAND AND ALPINE PLANTS 397 



condition seems to be a soil poor in lime and other mineral 

 salts ; it thus differs from a marsh, which is richer in 

 mineral salts. The Bog-moss grows rapidly; its closely- 

 packed shoots, and the narrow channels in its leaves, form 

 a series of capillaries which enable the plant to draw water 

 up to a considerable height, and hold it firmly. As the 

 upper branches continue their growth, the lower, older parts 

 die, and, decaying very slowly, form beds of peat often of 

 great thickness. If a piece of such peat is examined the 

 remains of the Bog-moss are clearly seen. On bogs thus 

 developed are found the Sundews (Fig. 232), Butterwort 

 (Fig. 234, 1), Cotton-grasses, White Beak- rush (Rhyncho- 

 spora alba), Purple Moor- grass (Molinia), Bog Asphodel 

 (Narthecium ossifragum) , Marsh Andromeda (A. Polifolia) ; 

 and on the drier parts many shrubby heath-plants, e. g. 

 Cross and Fine-leaved Heaths, Ling, Crowberry (Fig. 253), 

 Bilberry, Cowberry, Cranberry (Fig. 254), Cloudberry 

 (Rubus Chamaemorus), also the Sweet Gale or Bog Myrtle 

 (Myrica Gale) and Creeping Willow (Salix repens). 



Alpine Plants 



Plants growing on the tops of mountains have many diffi- 

 culties to contend with. The air is rarefied ; the winds, 

 often very drying, are at other times moisture-laden ; cold 

 driving mists alternate with bright sunshine ; hot days are 

 followed by cold nights ; snow lasts long, especially in the 

 hollows, and the soil is thin and well drained. 



In spite of these varied and fluctuating conditions, many 

 plants grow here, but they develop dwarfed, tufted, and 

 other xerophytic growth-forms, well adapted to such a 

 habitat. Many of the species occur only at great altitudes 

 and in the Arctic regions. A few are found on the sea- 

 coast, but they are absent from the intervening lowlands, 

 e. g. Scurvy-grass (Cochlearia spp.), Sea Campion (Silene 

 maritima), Sea Plantain (Plantago maritima), and Sea Pink 

 (Statice maritima). The leaves are often up-rolled as in 



