LICHENS. 163 
irregular in form, inodorous and insipid. Pallas, 
the Russian naturalist, observed it on the arid 
mountains, and the calcareous portions of the 
Great Desert of Tartary. Mr. Eversham collected 
it on the steppes of the Kirghiz to the north of the 
Caspian Sea. It has been seen on the Altai 
range, in Anatolia, in South America, and recently 
in Algeria by Dr. Guyon. It occurs in irregular- 
shaped fragments, varying in size from a pin’s- 
head to a pea or small nut; and when seen in its 
native sites, is apparently attached to no matrix 
whatever, and has no fecula in its composition. 
In medicine, lichens were at one time very 
highly esteemed. In the days of Aldrovandus 
and Paracelsus, who added the study of alchemy 
and the occult sciences to that of plants, they 
were extensively employed in the preparation of 
sympathetic ointments, and in the various distil- 
lations connected with the search for the elixir- 
vite and the universal solvent and nostrum. 
Wonderful cures were ascribed to a particular 
application of them; and in the works of th 
botanists of the middle ages, we find long an 
elaborate observations upon the peculiar virtues 
of species developed upon the oak, the pine, and 
the beech. The common dog-lichen (Péltidea 
canina)—a species everywhere abundant on moist 
banks and turfy walls, and easily distinguished by 
