EARTH COVERINGS 



289 



nature and a compact surface to withstand the 

 elements. 



This is perhaps even truer of the gray lichens 

 that cling to the loose bowlders on the moun- 

 tain-side and color the barren crags and exposed 

 rocks of the peak. They are the hardiest, and 

 it is thought, geologically, among the earliest, 

 of all plants, making a bed for the flora of the 

 world by gathering about themselves grit and 

 mould from the rock. Sun, wind, rain beat 

 full upon them, but tenaciously they hold upon 

 the stone, never moving, scarcely ever changing 

 color. Sometimes called parasitic plants, they 

 are really the protective coverings of the stone, 

 as the mosses and the grasses are the coverings 

 of the earth. The long-stemmed sea-weeds that 

 cling about the coast bowlders the algce that 

 ward off the thrust of waves and the grind of 

 surges are the ocean cousins of these moun- 

 tain lichens. We know how the alga cover and 

 color the coast rocks, but we have, perhaps, less 

 knowledge of the color-changes wrought on the 

 mountain's peak by the lichens. The staining 

 and what is called the " weather-beaten " look 

 of rocks are largely their doing. The clean- 

 faced bowlder dug from the soil and the light- 

 ning-broken surface on the mountain wall are 



Gray 

 lidien, 



Rock- 

 staining by 

 lichens. 



