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Cephalodia:
dark, wart-like structures that contain cyanobacteria, which can be found on the thallus
of lichens with green algae (typical of a few species, e.g. of some
Peltigera
).
Central chord
of
Usnea
: In the genus
Usnea
the thallus is thread-like and the central part of the
medulla forms a compact structure similar to a wire. It can be easily seen by stretching the branches.
The central chord of
Usnea
sometimes may be pink-coloured.
Papillae and fibrils
of
Usnea
: structures similar to warts or wimpers, respectively, on the branches
of some
Usnea
species.
Pustules
are sometimes present on the upper surface of some lichens (e.g.
Collema
).
