THE PAGE OF NATURE. 89 



been appointed, as the pioneers or precursors of all other 

 land vegetation. What could be better adapted to with- 

 stand the fury of the storms that beat upon their exposed 

 places of growth than the crustaceous, powdery, or leaf- 

 like expansions which they often assume, hard and inse- 

 parable almost as a portion of the rock itself] Then their 

 capacity of extracting their nourishment principally from 

 the surrounding atmosphere ; the curious property which 

 they possess of continuing for years without undergoing 

 any perceptible change ; their strong persistent vitality by 

 which they are, able when scorched by the summer sun- 

 shine, deprived of all their juices, and reduced to shape- 

 less, hueless masses, which crumble into powder under 

 the slightest touch of the hand or the foot to revive 

 again when exposed to the genial influences of the rain, 

 assume their fairest forms and hues, and develop their 

 organs of fructification for the dispersion of their kind ; 

 and lastly, the facility with which they can replace por- 

 tions of their substance that have been torn away by 

 storms, broken by the tread of man, or eaten by animals ; 

 all these qualities illustrate the wonderful adaptation, in 

 their structure and habits, to the unfavourable circum- 

 stances in which they are often placed. Furnished by 

 such powers as these, wherever they fasten their tiny 

 fangs the process of disintegration commences ; and 

 though carried on slowly and imperceptibly, though ages 

 may elapse before any apparent effects have been produced, 

 except the increase of individuals and the more shaggy 

 and picturesque appearance of the rocks, yet the object 

 of that steady, ceaseless labour will one day be accom- 

 plished ; and it is humiliating to the pride of man to 



