188 LICHENS. 



are formed. Lichens are either crustaceous or frondose. 

 Their fruit is of two kinds, the more perfect form being 

 deposited in concave or convex shields, and lines ; the 

 less perfect in powdery warts. These sturdy plants seem 

 strangely independent of the substance on which they 

 grow. Some flourish on the hardest rocks, others prosper 

 on healthy trees : they will bear all vicissitudes of 

 weather ; for though they seem to dry up and die in the 

 hot sunshine, yet the first rainy day enables them to 

 expand again, and resume the business of their life. 

 They have a wonderful power of retaining moisture, and 

 also of collecting it ; for if there is any damp in its 

 neighbourhood, the lichen seems to attract it to itself. In 

 dying they deposit a subtle acid, which wears away the 

 rock on which they grew, and thus forms earth fit to 

 nourish minute plants of higher organization. It was this 

 capacity in the lichen to which the poet alludes, when 

 describing the gradual rise and vegetation of a coral 

 island — 



" But soon the lichen fixeth there, and dying, diggeth its own grave, 

 And softening suds and splitting frosts crumble the reluctant 

 surface." 



But the progress of such vegetation must be at a rate 

 inconceivably slow ; for, although the lichens attain 

 maturity quickly, they are very long before beginning to 

 decay. Mr. Berkeley states that he has noticed some for 

 twenty-five years remaining in an unaltered state. 



The first use of the lichen had long been familiar to 

 me : but I was astonished to find many other uses for 

 one or other of the tribe. As dyes, as food for animal 



