Endohyalina species either form a thin, tightly attached crust (a
crustose thallus) on the
substrate or live on other lichens, in which case their own
thallus is reduced to the point of being invisible. When present, the
photosynthetic partner is a single-celled
green alga (a photobiont).
Sexual fruit-bodies are small, black
apothecia of the type: they begin buried in the thallus and soon become flush with or slightly raised above the surface. A rim of thallus tissue (a ) is lacking or soon erodes, so the black appears sharply delimited. Microscopy reveals only a rudimentary outer wall () whose dark outer zone contains
hyphae with somewhat swollen cells, while the inner zone grades into the colourless tissue of the
hymenium. The hymenium itself may contain scattered oil droplets and sits atop a pale- to dark-brown . Inside each apothecium, unbranched
paraphyses stand among
Bacidia-type
asci. The paraphyses terminate in enlarged cells capped by a dark brown pigment, giving the inner surface a tufted appearance. Mature
ascospores are small,
ellipsoidal to spindle-shaped, divided once by a cross-wall (
septum) and darkening to brown except at the paler ends. Their internal walls thicken in characteristic patterns (chiefly the
Dirinaria type, but intermediate forms towards
Milvina-,
Physconia- or
Pachysporaria-types also occur); the thickenings appear before the septum forms, a
developmental sequence known as "ontogeny type B". The spore surface ranges from smooth to minutely wrinkled.
Vegetative reproduction takes place in sunken
pycnidia, which release colourless, rod-shaped
conidia. Chemical analyses have detected a suite of
secondary metabolites, including
diploicin,
fulgidin,
isofulgidin, and a range of related
depsidones such as
dechlorodiploicin,
caloploicin,
brialmontin 1,
atranorin, and several
secalonic acids. ==Species==