MOSSES IN EUROPE, AND THEIR ASPECTS IN NATURE. 33 



mondii, Ditrichum glaucescens, Polytrichum sexangulare, Amphoridium 

 Lapponicum, Encalypta commutata and rhabdocarpa, Andrecea cras- 

 sinervia, petrophila, alpestris and obovata, Hypnum sarmentosum, 

 callichroum, Bambergeri, sulcatum, &c., Myurella j'dacea and 

 apiculata. 



5. — The Supra-Alpine Eegion, reaching above the limit of 

 Pinus Pumilio and Betula nana to the line of perpetual snow. 



Here we have vast sterile rocks, some beaten and lashed by every 

 tempest, others constantly irrigated by streams from the melting 

 glaciers, with patches of short grass and deposits of black earth, 

 often mixed with detritus from the rocks above. In the middle 

 zone this region lies between 6,800 and 8,300 ft., in the northern 

 from 4,800 it descends gradually to below 2,800. Although the 

 line of perpetual snow does not touch our Scotch mountains, we 

 have snow fields more or less extensive lasting through the sum- 

 mer, as on Ben Nevis and the Cairngorm range, and we have some 

 of the characteristic mosses of this region, as Conostomum, Bryum 

 demissum, acuminatum, Ludwigii, and polymorphum, Pottia latifolia, 

 Dicranum fulvellum, Grimmia Doniana, contorta, elongata and mon- 

 tana, Polytrichum sexangulare, Andreosa nivalis, alpestris and 

 obovata, Hyp. glaciate, uncinatum, sarmentosum, arcticum, &c. 



I may now say a few words on the various habitats affected by 

 mosses, some of which, no doubt, have come under your notice, if 

 only as the little Tortula muralis, which raises its fruit stalks in 

 serried ranks between the bricks of our garden walls, or the Bryum 

 argenteum and Ceratodon purpureus that overrun neglected paths. 

 These, however, are sufficient to teach you many points in the 

 structure of the class to which they belong, and they will show you, 

 also, that mosses are pre-eminently social plants, that they never 

 occur as solitary individuals, but live in densely aggregated 

 colonies, which unite with others of various kinds, and thus form 

 that verdant carpet which, as Prof. Schimper well observes, " ani- 

 mates with brightness the highest mountains, inaccessible to more 

 perfect plants, enlivens woods impervious to the sun's rays, and 

 protects the earth against the drying and congelation equally fatal 

 to vegetable and animal life." A very little observation will tell 

 us that certain habitats have their constant occupants, and thus an 

 old wall becomes a very botanic garden to the Bryologist, Such 

 we may term mural species, and foremost among them place the 

 never failing Tortula muralis, and its pretty constant companion, 



