346 MOSSES AND LICHENS. 



and many of the lichens, to which cold is more 

 congenial than heat, and which are brittle and 

 crumbling during the hot season, are in the 

 prime of their vigour in winter ; and, perhaps, by 

 their agency the very first steps in the progress 

 of fertility are accomplished. If there is but a 

 rock, or any thing except loose and dry sand, 

 and moisture, and a temperature the least shade 

 above freezing, there is certain to be a moss or a 

 lichen of some description or other ; and however 

 untoward the circumstances are, that lichen or 

 moss will keep growing until it forms something 

 like a vegetable mould in which other plants will 

 in time take root. 



Those mossy coverings which spread and thicken 

 upon the surface in cold places and cold weather, 

 protect the naked parts of the earth from the 

 severe action of the cold ; and answer, in places 

 where the snow does not lie, nearly the same 

 purpose that the snow answers where it does. In 

 some respects, indeed, they answer more impor- 

 tant purposes. They are most abundant in humid 

 places where the snow does not continue, though 

 it occasionally falls ; and there they protect the 

 earth against the alternate action of the rains and 

 the frosts. If the earth were bare, the frost, 

 which is of much service to the vegetation of the 

 coming season, by breaking down the clods that 

 have been indurated by the drought of summer, 

 would, in the course of one variable winter, ren- 

 der the whole so soft, that the rains would wash 

 all the mould of the heights into the valleys, 

 and the portion of land fit for bearing vegetables 

 of any kind, would decrease every year. Nor 

 would there be merely a decrease of the produc- 



