164 FIRST FORMS OF VEGETATION. 
its livid brown wrinkled leaves, and red, nail-like 
fructification—was formerly employed, at the sug- 
gestion of the celebrated Dr. Mead, as a cure for 
hydrophobia, hence its specific name ; but if it ever 
effected a cure, it may be pretty safely asserted 
that it was more by the aid of a strong imagination 
than by any inherent healing power in the plant 
itself. Another species of the same family (Ped¢z- 
dea aphthosa), with a remarkably vivid green thallus, 
growing by the side of mountain streams, was in 
high repute at one time asa powerful anthelmintic, 
and is still used by the Swedish peasants, when 
boiled with milk, as a cure for the aphthe or 
thrush in children. When the primitive principle 
that ‘like cures like’ and the strange ‘Doctrine 
of Signatures’ as it was called, formed the basis of 
all medical treatment, several lichens were em- 
ployed for the cure of diseases, on account of 
their fancied resemblance to the organs or parts 
of the body affected. Among such lichens the 
species in greatest favour was probably the lung- 
wort (Sticta pulmonaria), which grows in im- 
mense shaggy masses on trees and rocks in sub- 
alpine woods. From the resemblance of its reti- 
culated and lobed upper-surface, usually of a 
greyish-brown colour, to the human lungs, it was 
highly recommended as an infallible cure for all 
diseases of these delicate organs. The beautiful 
