whether the fibrous appearance in the central parts belongs
really to the plant or to the soil. The internal substance is
green under the brown superficial coat, and whitish towards
the base. Were all other distinction wanting, the plant
would be strongly marked as a species by the singular nature
of the apex of the tubercles, which, from its minuteness, and
the similarity of the colour to that of the thallus, is perceptible
only on close inspection by the naked eye, but, under
a glass, has, when perfect and in a dry state, altogether the
appearance of a little flat grey soredium *. When wet, it is
rather more protuberant, and presents a very narrow black
ring surrounding a grey point. The tubercle itself is globular
or slightly conical, and occupies the whole thickness of
the thallus. The shell is black, thickest towards the apex,
and filled with, and investing in every part, a colourless
jelly-like nucleus, which contains most minute clavate
thecae, and shrinks in drying into a scarcely discernible
whitish film.—W. B.
* See Ack. Meth. IJch. p. xxi.