the tubercle. They are globular, scarcely half the size of
poppy-seed. Their shell is apparently single^ thin, and pale
brown, except at the apex, which alone emerges, where it
is somewhat thickened, dark brown, or even black, and
occasionally polished, but more generally of a rather prui-
nose appearance, as if obscured by a film from the surface
of the crust. The exposed part, a mere dot to the naked
eye, is convex, yet scarcely more prominent than the raised
circumference of the wart, at length pierced with a rather
large, and in general regular, round orifice. When moderately
magnified, it much resembles in appearance the globule
of an Isidium. The nucleus is brownish, wax-like,
solid, or with a very minute central cavity when dry ; more
gelatinous when wet, and paler, with darker striae spreading
from the centre perceptible under a powerful magnifier.
Acharius would perhaps have placed this singular Lichen
in his genus Porina, to the species of which it has some resemblance
in the warts that inclose the tubercles, as well
as in the solid wax-like substance of the nucleus of the tubercles
themselves. Yet the manner in which their apex
usually emerges appears to point out a closer affinity to the
other Verrucarice. It is, in fact, one of the many links which
connect the Pyrenulce of Acharius with his Endocarpa. It
has the pale, thin, and apparently single perithecium of the
latter, and resembles the former in the structure of the crust.
V.fuscella, t . 1500, and the very nearly allied V. tephroides,
t. 2013, are similarly intermediate.
Lichen obscurus, Engl.Bot. 1752, (scarcely theOpegrapha
ohscura of Persoon, or the Arthonia obscura of Acharius,)
however different from the present species in other respects,
agrees with it in the structure of its tubercles, and must be
referred to the same genus. It is only when the tubercles
become confluent that it assumes the appearance of an A r thonia.
W. B.
V E R R U C A R I A Hookeri.
Hookerian Verrucaria.
CRYPTOGAMIA Uchenes.
Gen. 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.
Spec. Char. Crust thick, of pure white tumid tarta-
reous scales covering a black spongy substance.
Tubercles ampulliform, black, immersed, except
the conical or truncate apex.
H i t h e r t o observed, as far as we are informed, only
on dead mosses on the micaceous soil of Ben Lawers, in the
hollow near the summit in which Saxifraga cernua grows.
It was discovered, in 1808, by the writer of the present page
in company with the distinguished botanist whose name he
wishes it to bear.
Very unlike to every other Verrucaria with which we are
acquainted both in thallus and in fructification. The thin,
turgid, somewhat lobed, tartareous scales are similar in figure
to those of L.frustulosus, t. 2273, but of a much smaller size.
Their surface appears smooth to the naked eye, minutely
rugged under a glass. Their internal substance is green.
They grow either scattered, or. crowded more or less closely
into small patches, which bear a general resemblance to those
of L . aromaticus, L . desertorum, and some others of the
Acharian Lecidece. The black substratum, in which the
tubercles are immersed, is probably analogous to the radicles
of some of those Lecidece, or to the substance upon
which the scales of several of the smaller species of Endo-
carpon are seated. It is of uncertain thickness, imbibes
water freely, and is not always easily distinguishable from
the decayed moss upon which it grows. A question may