2692. (Pig. I.)
ARTHONIA impolita.
Pruinose Arthonia.
CRYPTOGAMIA Lichenes.
Gen. Char. Apolhecia solids deformed, without a
margin, sessile or immersed.
Spec. Char. Crust somewhat tartareous, thin, cracked,
uneven, white. Apothecia immersed, flat,
confluent, brownish lead-coloured, pruinose.
Syn. Arthonia pruinosa. Ach. Lick. Univ. 147. t. J.
f . 3. Syn. 7.
Lichen impolitus. Ehrh. Crypt.
Yerrucaria impolita. Hoffm. FI. Germ. v. 2. 172.
Parmelia impolita. Ach. Meth. 160.
O f frequent occurrence on boarded buildings, and on
the rugged bark of old oaks.
Crust in an early stage roundish, with a narrow border of
pale cobweb-like fibres; at length wide-spread, somewhat
tartareous, but mostly thinner than the shell of a hen’s egg,
variously cracked and uneven, except in very young specimens;
the surface more or less purely white, of a powdered
appearance in general; internal substance yellowish green in
the living plant. Apothecia immersed, flat or slightly tumid,
of an irregular rounded or oblong figure when most simple
and separate, but usually confluent, and often so numerous
that great part of the crust is almost obliterated or merely
forms small tumid plicate borders to the shapeless, crowded,
frequently angular clusters; their surface usually so pruinose
as. to render them inconspicuous unless closely inspected,
and in this case their hue is glaucous, or a dull lead
colour; sometimes more bare and of a blackish, or occasion