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CRTPTOGA MIA Alga.
G en. Char. Male, {battered warts.„
Female, fmooth (hields or tubercles, in which the
feeds are imbedded.
Spec. Char. Cruftaceous, whitifh. Shields black,
confluent, in concentric circles, imbedded in the
cruft.
S yn. Lichen concentricus. Davies, 2>. of Linn. Soc.
v. 2. 284.
L . petræus. Jacq. Coll. v. 3 . 1 1 6 . t. 6. / . 2, a. a. a.
F OUND on rocks of whin-ftone in the parilh of Whitford,
Flintfhire, by the Rev. Mr. Hugh Davies, F. L. S. The cruft
is fomewhat mealy, very thin, of a greyilh white. The ftiields
fcarcely rife above its level, and are remarkable for being
arranged in concentric lines, fometimes forming feveral very
regular circles, one within another, with a few difperfed {hields
between. The {hields are fmali, black, opaque, concave, with
a margin generally white, particularly in the young ones.
Their outline is feldom quite circular, efpecially as_ they are
moftly crowded together in lines, fo as to force one another
into an angular {hape, and to become in a manner confluent.
That this is the plant of Wulfen, publiftied by Jacquin
in his Collectanea above quoted, there can be no doubt, as the
defcription and figures exaftly agree with ours. With refpect
to thé fynonyms, which made Mr. Davies uncertain about it,
they are unqueftionably wrong, as the fynonyms of Wulfen
(otherwife an excellent botanift) too often are. The name
concentricus is fo very apt and fo ftrikingly characleriftic, we
could not hefitate about preferring it to the unmeaning one
of pet raus.