34 R. BRAITHWAITE ON THE GEOGRAPHICAL DISTRIBUTION OP 



Grimmia pulvinata, associated with which are Tortula revoluta, 

 Bryum ccespiticium, argenteum, and capillare, Hypnwm sericeum 

 polymorphum, tenellum, murale, &c. Roofs of outhouses, both of 

 thatch and wood, support Tortula ruralis, Didymodon Jlexuosus, 

 Ceratodon, Weisia cirrhata, &c. 



Passing next to the road sides and cultivated fields, we find on 

 clay soil Ephemerum, and most Phasca, Pottia truncata and minu- 

 tula, with Tortula ambigua, unguiculata, and fallax, Physcomitrium 

 pyriforme and Weisia controversa; on waste ground and gravelly 

 commons Funaria, Ceratodon, and Bryum argenteum, and where 

 these are heathy Polytrichum piliferum, Pogonatum aloides and 

 nanum and Dicranella heteromalla. 



From the mural mosses it is but a step to the saxicolous, or rock 

 inhabitants, for some species are common to both ; they vary how- 

 ever, according to the chemical constituents of the rocks, and ac- 

 cording to the altitude of the locality. Thus we have the silici- 

 colous, or those living on siliceous rocks, of which there are two 

 types, sandstone and granite, both widely distributed. 



Sandstone rocks are a favourite site for many species, the porous 

 nature of its particles permitting water to percolate freely, and 

 allowing them easily to fix their roots. Schistostega, Seligeria 

 pusilla, Tetrodontium, Amplwridium Mougeotii, Thamnium alope- 

 curum, Grimmia apocarpa, Amblystegium filicinum and commutatum, 

 are seldom absent from them. 



Granite, on the other hand, is more compact, yet often contains 

 those ledges and fissures in which so many alpine species delight 

 to establish themselves, numbering among them all the Andreasas, 

 Cynodontium polycarpum and Virens, Dicranum Scottianum, longi- 

 folium and hyperboreum, Grimmia, many sp., Hedwigia, Racomi- 

 trium, Ptychomitrium, Glyphomitrium, Orthotrichum rupestre, Sturmii 

 and Hutchinsice, Brachyodus, Campylostelium, A nodus, Mielich- 

 hoferia, Bryum alpinum, Muhlenbeckii and julaceum, Hyp. molle, 

 umbratum, demissum and StarJcii. 



Calcicolous mosses, or those of chalk and limestone, are often 

 peculiar to that formation, such e.g. as Eucladium, Seligeria several 

 sp., Weisia calcarea and 7*iq)estris, Trichostomum tophaceum and 

 fiexicaule, Grimmia anodon and orbicularis, Encalypta streptocarpa, 

 Bartramia GEderi and calcarea, Hypnum tenellum, &c. 



Another group which adds much to the enjoyment of sylvan 

 scenery, is the arboricolous, or those residing on living trees — the 



