38 FOOTNOTES FROM 



beneath. In such hermit seclusions the botanist may 

 expect to reap the richest harvest of species. Mosses 

 occasionally select very singular places of growth ; and 

 notwithstanding the minuteness and profusion of their 

 seeds, the facility with which they can be disseminated, 

 and their insensibility to ordinary physical conditions, 

 are, specifically considered, sometimes very much re- 

 stricted in their geographical range. Several kinds are 

 found in this country only on the summits" of the highest 

 Highland mountains, covering the barren soil with a 

 thin film of verdure, or creeping over the weather-beaten 

 rocks in tenacious dark-coloured clusters or tufts. These 

 species are identical with those found on the plains of 

 the Arctic regions and the hills of Lapland and Green- 

 land, where they occur not merely in isolated tufts, as 

 we find them in this country, but carpeting the ground 

 for many yards, and imparting a verdant hue to the 

 mountains and valleys. This circumstance would in- 

 dicate that their original centre of distribution exists in 

 these dreary regions, and that from thence they have 

 been disseminated over the British and European moun- 

 tains. The Alpine species are exceedingly restricted, sel- 

 dom being found lower than 3000 feet, and often ascend- 

 ing to a height of 4000 feet on the British hills, and 

 8000 feet on the Alps of Switzerland and the Pyrenees ; 

 the isothermal line of these altitudes corresponding with 

 the plains of Lapland and the level of the sea-shore 

 in the Arctic regions. Along with the small moss-like 

 Alpine flowers with which they grow, they must have 

 been wafted down to the Highland mountains, either as 

 germs or as full-sized plants, growing undisturbed in 



