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L I C H E N tigillaris.
Yellow Rail Lichen.
CRYPTOGAMIA Algos.
G en. Char. Male, scattered warts.
Female, smooth shields or tubercles in which the
seeds are imbedded.
S pec. Char. Crust spreading, cracked, rugged, smooth,
yellow, rising into warts which bear the shields.
Shields minute, black, flat, with a black border.
Syn. Lichen tigillaris. Achar. Prod. 67.
Lecidea tigillaris. Achar: Meth. 46. t. 2. f 1.
M r . DICKSON first mentioned this to us as a British
species. He gathered it on trees in Enfield Chace. Mr. E.
Forster communicated the specimen here represented from a
barn at Walthamstow. The same is found also on barns, rails,
and old paling at Loughton, Essex.
The crust spreads in an indeterminate manner, and in a
young state is loosely scattered over the decaying wood. Its
colour is a bright conspicuous yellow when dry ■ greenish occasionally
when wet. When perfect the crust is minutely
cracked and rugged or warty, yet the surface is smooth, not
powdery. Each of the larger and more prominent warts bears
oh its top a minute sessile black shield, surrounded by a
smooth black border.
The minuteness of the shields has, perhaps, caused this
Lichen to be overlooked, notwithstanding its striking yellow
colour, as something in an imperfect state.
The acuteness and accuracy of Dr. Acharius first determined
its characters, nor can any species be more distinct.