LICHENS. 99 
line of black like a mourning letter. It spreads 
over the bark of trees, particularly the beech, the 
hazel, and the ash. On the birch-tree—whose 
smooth, snow-white, vellum-like bark seems 
designed by nature for the inscription of lovers’ 
names and magic incantations—it may often be 
seen covering the whole trunk. The fructification 
consists of long wavy black lines, sometimes 
parallel like Runic inscriptions ; sometimes arrow- 
Fic. 7,—OPEGRAPHA SCRIPTA. 
headed, like the cuneiform characters engraved 
upon the monumental stones of Persepolis and 
Assyria; and sometimes gathered together in 
groups and clusters, bearing a strong resemblance 
to Hebrew, Arabic, or Chinese letters, 
In that well-known and interesting work, Travels 
in Tartary, Thibet, and China, by the French 
Lazarists Huc and Gabet, there is a long descrip- 
tion of a very remarkable phenomenon called the 
