Acrocordia usually presents as a thin, patchy crust that spreads flat across its
substrate or sits partly submerged within it. The
thallus is whitish to pale grey and lacks a protective outer skin (), so individual fungal cells merge directly with the bark or rock surface. Threaded through this tissue are microscopic filaments of the green alga
Trentepohlia, whose orange-tinged cells provide the lichen's
photosynthetic power. The species favour mildly
alkaline substrates, growing on the bark of broad-leaved trees or on damp, base-rich rock faces. Fruiting bodies are in the form of
perithecia—tiny flask-shaped chambers embedded almost entirely in the thallus. From above they appear as scattered black dots (occasionally pinkish or whitish) that may coalesce into small clusters. Each perithecium is wrapped in a brown-black wall called the , which remains unchanged in
potassium hydroxide solution (KOH), and encloses a paler inner sphere (the ). The interior is filled with a clear gel traversed by slender, sparsely branched —supporting filaments that remain intact even when the spores are released. Unlike many flask-shaped lichens,
Acrocordia lacks , the short hairs that often line the pore. The spore sacs (
asci) are cylinder-shaped, split open along their length when mature (), and possess a swollen ocular chamber at the tip; above this lies a faint, hemispherical cap that stains with
Congo red. Each
ascus normally holds eight colourless
ascospores arranged in a single row. The spores are
ellipsoid to short-cylindrical, divided by a thick median wall into two almost equal halves; occasionally one or two additional thin walls form. Their outer coat () is covered in tiny wart-like bumps that give a rough appearance in water mounts but disappear when treated with KOH.
Asexual propagation occurs in immersed
pycnidia that release simple, colourless, ellipsoidal
conidia. No secondary
lichen products have been detected in the genus, so field recognition depends chiefly on the pale, immersed thallus, the KOH-negative black perithecia, and the minutely warted, two-celled spores arranged in a single file within each ascus. ==Species==