[ 964 ] J lo b
LICHEN confpurcatus.
Dujîy Lichen.
CRYPTOGAMIA Alga.
G e n . C har. Male, fcattered warts. Female, fmooth
{hields or tubercles, in which the feeds are imbedded.
Sp e c . C h a r . Cruft thick, greyith-white, cracked,
rugofe, at length mealy ; very white within.
Shields numerous, fcattered, minute ; at firft prominent
and pale brown ; then concave and black.
Me. D. TURNER firft dete&ed this Lichen on the old
Roman walls of Burgh caftle in Suffolk, afterwards at Scole
inn, Norfolk, and other places. We have obferved the free-
ftone church of Cawfton in the fame county in many parts
entirely encrutted with it, particularly the elegant carving at
the weft end. It feems always to choofe calcareous ftones,
whether of a finer or coarfer texture. We have not been able
to refer it to any fpecies in the work of Acharius, though we
are not without a fufpicion of its being his L. calcarius, a con-
iefture we may hereafter be able to confirm or difprove, but
in the mean while we would not withhold a plant fo totally
new to Britifti botanifts. . . „ ,
The cruft fpreads widely* and in xnoift weather may eaiily
be detached from the ftone; it is from half a line to nearly 3
lines in thicknefs, extremely white and chalky within, fplitting
perpendicularly, fo as to look fibrous. The l'urface is greyifli-
white, very rugged and unequal, cracked into fmall irregular
portions, warty and powdery with age, fo as to affume a dirty
or dufty afpeft, to which the innumerable young {hields of
various fizes, fprinkled over the cruft, like grains of clear
brownilh fand, alfo contribute. The fliields when at maturity
are ftill very fmall, in a great meafure immerfed in the cruft,
totally black, concave, with an entire elevated edge.