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 alge 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 alge 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 
lichens. 
Rock- 
staining by 
lichens. 
