2637. (Fig. 1.)
V E R R U C A R I A niveo-atra.
Snowy-crusted Verrucaria.
C&YPTOGAMIA Lichenes.
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 indeterminate, thin, rugose, somewhat
powdery, white. Tubercles very minute,
orbicular, half-immersed; their apex naked, depressed,
rugose.
A . S this Lichen, although by no means inconspicuous,
has been observed in but few places, it is probably rare. It
has been found on old timber in the wall of a house at
Bramber, Sussex, and on elms at Portslade in the same
county, and in various parts of Suffolk. The late Sir T.
Gage gathered it at Hengrave.
Crust spreading irregularly to considerable extent, extremely
thin, very minutely rugose, with more or less of a
powdery appearance, most often slightly cracked; snowy
white externally, especially when dry; internally, greenish
with a tinge of yellow. Tubercles mere dots to the
naked eye, very numerous, irregularly scattered, sometimes
crowded here and there in little clusters, and deformed by
mutual pressure ; otherwise more or less regularly orbicular
; for the most part nearly flat, sometimes more convex
but not much raised above the level of the crust in which
their base is immersed; their surface, full black or somewhat
pruinose, irregularly rugose in genera], whence the
minute orifice is usually difficult of detection. Nucleus
mostly obscure, but Mr. Sowerby found it pale and almost
filling the shell in the specimen that he has drawn.
In general appearance this Lichen approaches more nearly