over, with particles from the crust. They are brownish and
of a pruinose appearance when dry, black when wet. Their
orifice is a minute dot at first, and gradually enlarges so as
to become an irregular concave opening, often so wide as
to give the old tubercles the appearance of deformed patel-
lulae with an imperfect disk and a thickish distorted margin.
Their interior is greyish.
The general aspect of this Lichen is so much like that of
Lichen viridis of Schreber, Lepraria botryoides of English
Botany (not of Acharius), that it might easily be mistaken
for that plant, somewhat faded, and sprinkled with a minute
parasite. Under a glass, however, the crust is found to be
thinner and more coherent than that formed by the propa-
gula of the Lepraria, and the tubercles seem really to belong
to it. In an old state they resemble, as before observed,
deformed patellulae, and even more strikingly the young
and as yet sessile capitula of some of the Calicia. Still they
appear to be in reality the tubercles of a Verrucaria. Acharius
has observed of those of his V. trachona, that they in
some states so resemble those of V. leucocephala as to induce
a doubt whether the two species were distinct. In ours
there is occasionally some resemblance, but we cannot entertain
any such doubt. Of our other species of this genus,
only V. epigea (Lichen terrestris of English Botany) and
V. elceina bear even a general resemblance to V. trachona;
and a slight examination is sufficient to prove these very
different both in crust and in fructification.—W. B.
V E R R U C A R I A rauralis.
Wall 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, composed o f thin
scattered or confluent scales, between pulve-
raceous and tartareous, pale grey. Tubercles
prominent, nearly globose, unpolished, umbili-
cate.
S yn. Verrucaria muralis. Ach. Meth. 115. Lick.
Univ. 288. Syn. 95.
V. ruderum. DeCand. FI. Fr. ed. 2. v. 2. 318.
Sphaeria communis. Sowerby Engl. Fungi, t. 295.
upper figure.
V ERY common on walls, growing chiefly, but not exclusively,
on the mortar. The place of growth, and the
descriptions of Acharius and of DeCandolle, appear to
justify the references made above to the works of those
authors ; yet it is almost needless to observe, that a crus-
taceous Verrucaria, especially one of the more obscure species,
can hardly be determined with certainty from a mere
description, however excellent. Acharius originally regarded
his plant as the true Lichen calcarius of Linnasus ;
an error which he corrected in his Methodus.
Crust often scarcely perceptible; composed of minute
whitish scales, or flocculi, of an imperfect powdery look,
either scattered irregularly and separate, or approaching
each other and confluent here and there into more compact
and imperfectly areolate patches, the surface of which oc