OPEGRAPHA dendritica.
Tree-like Opegrapha.
CRYPTOGAMIA Algae.
Gen. Char. Seeds in black, linear, sessile, simple or
branched, bordered clefts, in an uninterrupted crust.
Spec. Char. Crust tartareous, determined, very white
and somewhat powdery. Clefts immersed, depressed,
without any elevated border, repeatedly branched,
zigzag, tapering at each end.
Syn. Opegrapha dendritica. Ach. Meth, SI. 1. l.f. 10.
R e s p e c t in g this beautiful species there is no doubt nor
difficulty. It has been found in Sussex by Mr. W. Borrer,
and in the New Forest by Mr. Lyell. Acharius only has described
it, from Spanish specimens, with an indifferent figure.
I t grows on the smooth bark of trees, in roundish, cream-
coloured, somewhat mealy, patches; the crust thin but tartareous,
spreading in a determinate manner, all the clefts radiating
as it were from the centre, and not extending to the
edge, which, for some distance, is smooth, uniform, and spotless.
It should seem as if the fructifying clefts were formed
by a shrinking in the central part of the crust, or as if that
part could not keep pace in dilatation with the marginal region,
and were over-stretched. Our figure expresses this better
than it can be done by words. The clefts are black, sunk
below the surface of the crust, and destitute of any margin,
except an occasional slight elevation of the crust, the proper
black border, usual in the genus, being scarcely perceptible.
Their form is waving, tapering very acutely at each end,
branched and forked in a most elegant manner, those furthest
from the centre being the most complicated.