218 CRYPTOGAMIA. 
the trees, rocks, or earth on which they grow, in an expan- — 
sion, thin like a crust, granulated, lobed, having imbricated 4 
scales, or sometimes consisting of a powdery layer; some 4 
resemble shrubs or corallines in miniature, growing erect on — 
the ground, or hanging from trees. This expansion is called 4 
a frond, thallus, or universal receptacle, and is of various q 
colours in different Lichens. The sporules are imbedded in 
the substance of the thallus, or scattered on its surface, and 7 
are often included in organs called apothecia, shields (scu- — 
tella), or tubercles. q 
Exampies.—Lepraria botryoides, a thin powdery green — 
crust, frequent in shady situations on trees, posts, rails, &c. 4 
Cenomyce coccifera (Lichen cocciferus), which resembles 4 
wine-glass; Graphis scripta, which resembles written cha- 
racters ; Parmelia parietina (Lichen p.), of a bright yellow 4 
colour, with Saucer-shaped apothecia, frequent on trees 4 
walls ; Lecanora murorum (Lichen m.), of an orange-colour, 4g 
frequent on rocks and stones. 7 
= Lichens are much used in dyeing, furnishing a red, purple, 
or crimson dye. Lecanora tartarea furnishes the Cudbear a 
of dyers. Arechil (Orchall), a valuable dye, is obtained from q 
the Rocella tinctoria. Litmus is prepared from this lichen. 4q 
Lecanora perella affords a purple or crimson dye, the orseille 4a 
de terre of the French. These are the principal kinds, but q 
_ there are many others which abound in colouring matter- 
Economica Prorerties.—The Lichens contain a con- 
siderable quantity of starch and mucilage, which renders — 
them very nutritious. The Tripe de Roche, on which the 
Canadian hunters frequently subsist, is a Lichen, called 4 
Gynophora. The rein-deer, which are so useful to the Lap- — 
__ landers, feed on the Cenomyce rangiferina, or Rein-deet 
Moss. Cetraria islandica (Lichen islandicus or 
