78 



POPULAR HISTORY OF LICHENS. 



pleasure in referring the student, — eloquently describes the 

 Lichens as " one means of that gradual but never-ceasing 

 disintegration or decay, which is wearing down the densest 

 and loftiest pinnacles of the earth/'' We shall select for il- 

 lustration of the part which they play in the formation of soil 

 fitted for the germination and growth of higher plants, a 

 saxicolous, crustaceous species, growing on the bare quartz 

 summits of some of our Highland mountains, — 



" Cradled in storms, and nurtured by the hand 

 That clothes with, varied forms the face of earth, 

 And fills creation's fields with joy and mirth : " 



or we may suppose its habitat to be the bare lava of a volca- 

 nic district, or the equally sterile surface of a newly upraised 

 coral island. The delicate spores of such a species have 

 been wafted thither by a breeze, or washed to its surface by 

 a shower : they germinate, and develope a thallus which be- 

 comes adherent to the rocky surface by a process of disin- 

 tegration. From the atmosphere chiefly, and from the rock 

 perhaps to a slight extent, the plant derives nourishment, 

 grows, and in course of time dies, thereby adding to the 

 thin stratum of mineral soil, w T hich it has produced, a 

 thicker layer of vegetable soil. This soil is now suited for 

 fruticuiose or foliaceous Lichens; these in their turn decay, 



