cle (a). When the crust spreads from the smooth bark
into the cracks of young oaks, and when it grows on more
rugged bark, it is more widely effused and whiter, seldom
polished, and not rarely of a powdery appearance. The
tubercles in this state of the plant, are more numerous, more
irregular in size, more prominent, often crowded and confluent,
not rarely of a pruinose appearance; and their apex
is very often umbilicate (c).
This is an obscure and puzzling Lichen. In the state
first described it approaches near to V. olivacea, although
the whiter crust, and the broken appearance of the older
tubercles, tolerably well distinguish it. The latter character,
and the thicker shell and greater protuberance of the
tubercles, distinguish it from V. cinerea of Persoon, (Lichen
stigmatellus, t. 1891 of the present work,) without adverting
to the differences of the crust. The blackened specimens
bear some resemblance to V. rhyponta, but the much greater
size and different structure of the tubercles will prevent
their being mistaken for that species; nor is the crust, in
reality, less truly different. The second state is so unlike
the first, that the two might well be thought distinct, did
not specimens like that drawn at <z, c, occur, in which the
crust of the same individual, spreading on young oaks from
the smooth epidermis to the cracks of the bark, bears in the
one part the former, in the other the latter appearance.
This state is possibly V.farrea of Acharius ; but, should it
prove so, we should hesitate to adopt the name, as neither
applicable nor intended to apply to the other form of the species.
It very closely resembles V. gemmata, and were it not
for the impossibility of separating it from the former, doubt
might arise whether it ought not to be united to that species.
The tubercles, however, do not attain half the size usual in
V. gemmata, although they seem liable to all the same variations
in. figure, except, perhaps, that they never become
mammillated. Their shell, also, passes under the base of
the nucleus, which is not the case in V. gemmata; at least
not usually, for we are by no means certain of the constancy
of this apparently essential character.—W. B.
V E R R U C A R I A gemmata.
Large-fruited Bark Verrucaria.
CRYPTOGAMIA Lichenes.
G e n . C h a r . 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 p e c . C h a r . Crust indeterminate, almost filmy, continuous
or somewhat cracked, nearly smooth,
whitish. Tubercles large, prominent, hemispherical
or deformed, naked or invested with
a very thin film.
Syn. Verrucaria gemmata. Ach. Meth. 120. t. 3.
ƒ. 1. Lich. Unw. 278. t. 4. ƒ. 2. Syn. 90.
DeCand. FI. Fr. v. 2. 315. Purton, v. 3. 162.
V. melaleuca. Ach. Meth. 117.
V. alba. Schrad. Spicil. 109. t. 2.ƒ . 3?
Lichen melaleucus. Ach. Prod. 15.
L. gemmatus. Ach. Prod. 17.
" W E are not aware that this Lichen is noticed in any
work on British plants besides Purton’s Midland Flora;
yet few occur more frequently on the trunks of trees, especially
on the ash.
The crust is scarcely more than a film, although sometimes
sufficiently thick to show an internal green substance
when cut. It spreads widely and indeterminately, except
that when several plants crowd each other their limits are
usually marked by a black line. Its surface is continuous
or variously cracked, smooth, in general, but scarcely polished,
sometimes a little rugged, and sometimes looking
almost powdery, of a white more or less pure, or, occasionally,
of a dirty grey or lead colour. Tubercles scattered,