Naetrocymbe usually reveals itself only through its fruit bodies. The fungus lives embedded within the outer bark of smooth‐trunked trees and develops little or no true lichen body (
thallus). Where present, the thallus appears as a faintly paler patch of tissue and, in some collections, may be loosely associated with orange‐tinged filaments of
Trentepohlia algae, though this partnership is optional rather than constant. Beneath the surface the fungal
hyphae weave through the bark, forming an inconspicuous network sometimes referred to as a subiculum. The
perithecia—the flask-shaped reproductive structures—look like minute dark dots that may be round or slightly elongated when viewed from above. Each is capped by a shield-like built from densely compacted fungal threads mixed with bark cells; this cap often spreads laterally, so the perithecia sit beneath a small, dark 'roof'. A much thinner, colourless to pale brown inner wall (the ) surrounds the central cavity. Microscopic inspection shows a mesh of delicate, freely branching threading a clear, non-
amyloid gel (that is, the gel does not turn blue in iodine-based
stains). The spore sacs (
asci) possess two functional wall layers that separate at maturity—a mechanism—and end in a faint . Each ascus contains eight colourless
ascospores that are club to narrowly cylindrical in shape. The spores have one, three, or occasionally more cross-walls and pinch sharply at each
septum; with age they may darken slightly and acquire a fine, warty ornamentation. A slender gelatinous commonly surrounds each spore.
Asexual reproduction takes place in immersed to slightly protruding
pycnidia whose walls share the same dark pigment as the perithecial caps. These chambers release , rod-shaped
conidia that remain colourless and lack internal walls. No
secondary metabolites (
lichen productss) have been detected by
thin-layer chromatography. The genus comprises about twenty
temperate species that occupy the smooth bark of living trees, functioning mainly as bark-dwelling
saprobes and forming only a casual, facultative association with algae in some situations. ==Species==