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OPEGRAPHA betulina.
Birch-bark Opegrapha.
CRYPT0GAM1A Algee.
Gen. Char. Seeds in black, linear, sessile, simple or
branched, bordered clefts, in an uninterrupted crust.
Spec. Char. Crust very thin, dilated, white, bordered
with black. Clefts mostly simple, prominent,
linear, with an extremely narrow disk.
Svn. Opegrapha betulina. Persoon in Ust. Ann.
fuse. 7. 31. t. 3. ƒ . 5, A, a. AcTi. Meth. 20.
Lichen betulinus. Ach. Prodr. 23.
T H IS occurs on the smooth bark of the common Birch, and
was sent us from near Yarmouth by Mr. Turner. The patches
are rather broad, white, smooth and somewhat shining, with
a thin brown or blackish edge, chiefly visible when the plants
meet and confine each other’s growth; otherwise the growing
margin is white and indeterminate. Clefts inclined to be parallel,
straightish, or slightly zigzag, linear, narrow, sometimes
tapering at each end to a sharp point, elevated, of a shining
black, scarcely powdery, in our specimens at least; their disk
less in diameter than the border on either side. Sometimes we
have found a few of the clefts here and there forked, or confluent,
which we have taken care to express, but such are very
unusual.