in Thoreau’s Journal:
P. M. – To Walden and Baker Bridge, in the shallow snow and mizzling rain.
It is somewhat of a lichen day. The bright-yellow sulphur lichens on the walls of the Walden road look novel, as if I had not seen them for a long time.
Do they not require cold as much as moisture to enliven them? What surprising forms and colors! Designed on every natural surface of rock or tree. Even stones of smaller size which make the walls are so finished, and piled up for what use? How naturally they adorn our works of art! See where the farmer has set up his post-and-rail fences along the road. The sulphur lichen has, as it were, at once leaped to occupy the northern side of each post, as in towns handbills are pasted on all bare surfaces, and the rails are more or less gilded with them as if it had rained gilt. The handbill which nature affixes to the north side of posts and trees and other surfaces. And there are the various shades of green and gray beside.