182 THE FLOWERLESS PLANTS. 



tion. They make their appearance on naked rocks, and 

 clothe them with a sort of fringe, holding fast on the rock 

 for security, and deriving their chief sustenance from the 

 atmosphere and particles of dust wafted on the winds 

 and lodged at their roots. They have properly, however, 

 no roots, neither have they leaves or stem ; yet they are 

 almost infinitely varied in their forms, hues, and ramifi- 

 cations. They grow in all places wdiich are exposed to 

 air and moisture, on the surface of rocks, old walls, fences, 

 posts, and on branches of trees. Some of the species are 

 foliaceous, resembling leaves without branches or any dis- 

 tinct or regular outline, and they are foimd mostly on 

 rocks. Others are erect and ramified like trees and shrubs, 

 but without anything that represents foliage. Such is 

 that common gray lichen that covers our barren liills, 

 which is a perfect hygTometer, crumbling under the feet 

 in dry weather, and yielding to the step like velvet, 

 whenever the air contains moisture. In similar places, 

 and growing along with it, is found one of the hepatic 

 mosses that produces those little tubercles — the fructifi- 

 cation of the plant — resembling dots of sealing-wax, 

 eagerly sought by artists who manufacture designs in 

 moss. But the most beautiful lichens are those which 

 are pendent from trees, consisting of branching threads, 

 of an ash-green color, and bearing little circular shields 

 at their extremities. These lichens give character to 

 moist W'Oods and low cedar-swamps, where they hang 

 like funereal drapery from the boughs and deepen the 

 gloom of their solitudes. 



Lichens, tliough inhabiting all parts of the eartli, are 

 particularly luxuriant in cold climates, thriving in extreme 

 polar latitudes, where not another plant can live. Nature 

 seems to have designed them as an instrument for prepar- 

 ing every barren spot with the means of sustaining the 

 more valuable plants. Xot only do they cause a gradual 



