THE PAGE OF NATURE. 77 



altitude, and the geological character of the rocks upon 

 which they are produced ; and thus several species and 

 even genera are necessarily rare and confined to particu- 

 lar localities. It may, however, be said of them in 

 general that they are cosmopolitan, universally distri- 

 buted over the surface of the globe, and capable of ex- 

 isting in almost every situation, from the calcined plains 

 of burning Africa to the snow-mantled pinnacles of icy 

 Spitzbergen. Placed almost at the lowest scale of 

 organization, they often require nothing more for their 

 conservation, than the moisture of the atmosphere pre- 

 cipitated on naked masses of rock ; and their simple 

 form and structure enable them to resist an amount alike 

 of heat and cold, sufficient to destroy all vitality in more 

 perfectly organized plants. In the Arctic regions 

 those outer boundaries of the earth, where eternal winter 

 presides these humble plants constitute by far the 

 largest proportion of the flora, and by their prodigious 

 development, and their wide social distribution, give as 

 marked and peculiar a character to the scenery, as the 

 palms and tree-ferns impart to the landscapes of the 

 tropics. In the southern hemisphere also, lichens almost 

 extend to the pole. They mark the extreme limit at 

 which land vegetation has been found, one shrubby 

 species, with large, deep, chestnut-coloured fructification, 

 called Umeafasciata, having been observed by Lieutenant 

 Kendal on Deception Island, the Ultima Thule of the 

 Antarctic regions. " There was nothing," he says, in his 

 interesting account of his visit to that island, " in the 

 shape of vegetation except a small kind of lichen, whose 

 efforts seemed almost ineffectual to maintain its exist- 



