are formed the tubercles, which are numerous, regularly
scattered, a small portion only of their upper part emerging,
sometimes several in the same areola, sometimes only one;
the exposed part is a mere point to the naked eye, sometimes
polished, sometimes not so, most frequently regularly
convex, sometimes slightly dimpled, occasionally marked
with a most minute dot at the centre, and not rarely of a
brownish hue in that part: the shell is thick and black, as
well in the immersed as in the protuberant portion, and
incloses a minute whitish nucleus.
Owing to the uninterrupted and even mode of growth,
this Verrucaria differs much in habit both from V. tephroides,
t. 2013, and from V. fuscella, t. 1500; yet so nearly is it
allied to the latter that it is now proposed as distinct with
considerable hesitation. V. fuscella is distinguished, however,
not only by the thicker, pulvinate, variously tumid,
and often deeply fissured thallus, but more essentially by
the. structure of the tubercles, which are much more minute,
and have the brown solid nucleus enveloped, in the immersed
portion, only in a thin pellicle of their own colour, and not
inclosed in every part in a thick black shell. It is by this
mark that Acharius distinguished his V. glaucina from
V. fuscella, regarding the latter as an Endocarpon*; and
V. polysticta might hence be supposed his V. glaucina, a
plant known to him only from British specimens communicated
by Mr. Harriman, were not the thallus of that Lichen
described as “ sordide albicans” within. But the whole
description of V. glaucina agrees well with old effuse
specimens of V. plumbea (Lichen plumbosus of' Engl. Bot.
2540,) such as we also long ago received, unnamed, from
Mr. Harriman.
There is a Lichen, probably undescribed, although common
on pebbles on the sea-shore, and found occasionally
on brick walls, which is scarcely distinguishable from
V. polysticta by the naked eye: as, however, the production
in question is a Lecidea, (or Gyalecta of Acharius,) it is unnecessary
to point out any less decisive difference.—W. B.
* In the Syn. Lick. p. 99. it is united with V. polythecia of the Lick. Univ.
as a variety of E . tephroides.