32 R. BRAITHWAITE ON THE GEOGRAPHICAL DISTRIBUTION OF 



the upper limit of growth of the beech, and extends in the southern 

 zone from an altitude of 5800 to 6800ft., in the middle zone from 

 1400 to 3400, and in the arctic northern descends into the plain 

 but little above the sea level. The features of surface are dense 

 woods of oak, beech, and pine, stony banks of streams and rocks, 

 all localities congenial to a rich growth of mosses. 



The most characteristic species are — Bryum crudum, elongatum 

 and Duvalii, Cinclidium Stygium, Amphoridium Mougeotii, Tetra- 

 phidacece, Bartramiacece, many Polytricha, Dicranacea and Grim- 

 miacece, Ulota Drummondii, Ludivigii, crispa and other Ortho- 

 trichaceas, Hypnum Halleri, crista-castrense, commutation, uncinatum 

 and revolvens. 



3. — The Subalpine Region reaches from the limit of the beech 

 to the upper limit of the Pinus abies, or spruce fir; the beech, 

 when it does occur, has ceased to be a tree, and takes the form of 

 a shrub. The chief features are pine and birch woods, rocky 

 streams, bare mountain pastures, turf bogs and rocks. The rapid 

 streams bring down many mosses from the higher region, which 

 become associated with others of the region below. 



In the northern zone the most characteristic mosses are — Andreosa 

 rupestris, petrophila and falcata, Blindia acuta, Ditrichum flexicaule 

 and homomallum, Distichium capillaceum, Grimmia apocarpa and 

 patens, Splachnum sp., Mnium cinclidioides and spinosum, Timmia. 

 Bartramia ithyphylla and Halleri, Oligotrichum, Pogonatum alpinum, 

 Polytrichum gracile, Pterogonium jiliforme, with Plagiothecium 

 pulcliellum and Muhlenbeckii. 



4. — The Alpine Region extends above the upper limit of the 

 fir, and commences with the Pinus Pumilio, or dwarf pine, ending 

 where that ceases to grow. 



In the northern zone the birch tree has disappeared, but the 

 Betula nana, or dwarf birch, as an erect shrub, occupies marshy 

 ground, and Salix Myrsinites, Menziesia ccerulea, Silene acaulis, 

 Diapensia Lapponica, &c, flourish abundantly. Many fine mosses 

 now appear for the first time, and yield a rich harvest to the col- 

 lector, as any who have explored the Highland mountains must 

 have observed. 



Among our British species I may enumerate Dicranella Grevil- 

 leana and subulata, Dicranum falcatum, Blyttii, glaciale, &c, Dis- 

 tichium, Rhabdoiveisia, Grimmia many sp., Dissodon, ' Tetraplodon, 

 Bryum julaceum, Muhlenbeckii, polymorphum, &c, Tortula Drum- 



