V E R R U C A R I A trachona.
Green Rock Verrucaria.
CRYPTOGAMIA Lichenes.
G en. Char. Tubercles of a different substance from
the thallus, simple, convex, not expanding, but
furnished with a central pore, and inclosing a
somewhat gelatinous nucleus.
S pec. Char. Crust indeterminate, thin, between pul-
veraceous and tartareous, continuous or slightly
cracked, greyish green. Tubercles small, prominent,
nearly globose, pruinose ; at length deformed.
Svn. Verrucaria trachona. Ach. Meth. Suppl. 16.
Lich. XJniv. 286. Syn. 96.
CjTATHERED by the late Miss Hutchins and the late
Sir T. Gage on slaty rocks in different parts of Ireland. It
has not been recorded as a native of any other country,
Sweden only excepted. Indeed the specimen communicated
to the Linnean Society by Acharius is somewhat
doubtful: yet the descriptions in his works agree so well
with the plant before us, that we venture to regard it as
his V. trachona.
The very thin crust, formed of confluent minute powder-
like granulations, spreads irregularly in patches an inch or
more in width. It appears a little rugged under a glass,
and is often slightly cracked when dry. Its hue is a pale,
usually dull, greyish green, scarcely changed by moistening.
The edge is grey, and of a dendritic or fibrous texture, as
if the crust were subtended by an extremely thin filmy base.
The tubercles are copiously scattered all over the crust,
so small as to appear mere dots to the naked eye, imperfectly
globose, raised above the thallus, but generally partially
clothed about their base and sides, and sometimes all