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L I C H E N geographicus.
Map Lichen.
CR T P TO GAMI A Alg,t.
G e n . C h a r . Male, fcattered warts.
Female, fmooth fhields or tubercles, in which the
feeds are imbedded.
Spec. Char. Cruftaceous, fmooth, yellow with a
black margin. Tubercles black, flat and irregular,
imbedded in the. cruft.
Syn. Lichen geographicus. Linn. Sp. PI. 1607.
Hudf. FI. An. 523. With. Bot. Arr. v. 3. 168.
Lichenoides nigro-flavum, tabuke geographic®
inftar pidum. Bill. Muß. 126. t. 18. ƒ. 5.
T H I S pretty and lingular production, which many a heedlefs
eye pafles by in its natural place of growth, but which, when
prefented to their notice, the moll incurious perfons cannot
help admiring, is found in elevated mountainous fituations on
the harder kinds of rocks, which it covers in large patches of
a hard fmooth infeparable cruft, of a bright yellow or greenilh
colour. The black undulating margin is fo extremely thin,
as to look like a mere ftain on the ftone; but when two plants
of this Lichen meet, they crowd one another’s margins into a
narrower line, and fometimes obliterate them, the yellow part
of the cruft rifing above them. This cruft is full of cracks,
efpecially in dry weather, like the mud of a pond when dried
up, and the whole is interfperfed with final], unequal and irregular,
black, opaque, angular, flightly concave tubercles or
fhields, exactly on a level with the cruft in which they are
imbedded. Hence the appearance of the whole gives fome
idea of a map, fprinkled with towns, and interfered with
rivers and boundaries of countries. We believe this fpecies is
never found on lime ftone. It is very doubtful whether L.
atro-virens be fpecifically diftinct from this.
The yellow of the cruft is fometimes changed, by age or
accident, to a grey, in which ftate it might be taken for another
fpecies.