Fellhanera species form a crust-like
thallus that adheres tightly to the
substrate but never develops a true protective skin (). When young the surface usually looks powdery or scurfy, ranging from whitish through grey-green to dull
ochre, and may break into shallow wart-like bumps or irregular cracks as it matures. Some species produce minute
soredia or —tiny, easily detached granules that propagate the lichen
vegetatively—yet even these remain embedded in the soft, corticolous crust. The algal partner () is a simple green cell about 5–12
micrometres (μm) in diameter, and there is little or no distinct , so the colony often merges imperceptibly into the bark or leaf it covers.
Fruiting bodies of
Fellhanera lichens are small, stalkless
apothecia that start flat and can become slightly domed; their may carry a delicate white bloom () and vary in colour from pale beige or yellow to dark brown. The rim of fungal tissue () is built of rounded cells that can erode with age, leaving the disc exposed. Within, a clear
hymenium reacts blue in iodine because each club-shaped
ascus has an
amyloid cap and coat; eight smooth, colourless
ascospores are produced, usually divided by one to seven transverse walls (
septa) and sometimes surrounded by a gelatinous sheath. Many specimens remain sterile in the field and instead develop plentiful immersed
pycnidia—minute pustules whose gaping
ostioles release tear-drop-shaped
conidia. Chemically the genus is characterised by
roccellic acid,
zeorin and occasionally
usnic acid or
asemone; dropping acetone on a scrap of thallus on a microscope slide yields a tell-tale white ring of precipitated substances, a quick test that separates
Fellhanera (chemically positive) from the look-alike genus
Bacidina (chemically negative). ==Species==