Phlyctis species are lichen parasites that either form a very thin, patchy crust on the host surface or lie almost entirely within it. When present, the thallus is smooth to slightly cracked, pale green-white to grey-green when fresh and fading to cream or pale brown as it dries; a delicate white prothallus often outlines the colony. The
photosynthetic partner is a minute
green alga of the genus
Symbiochloris. Some species produce powdery
soredia, which may remain as discrete dots or merge into larger, grainy patches. The sexual
fruiting bodies are minute
apothecia that stay immersed in the host
thallus, only barely emerging at maturity. Their entire surface can be hidden beneath a coarse white frost (). A thin, irregular borders the , while the is poorly developed. The carries , pale-brown pigment, and both the
hymenium and are colourless to faint brown. Slender
paraphyses thread the
hymenium; they branch only near the tips, have indistinct
septa, and end in slightly swollen cells.
Asci are broadly club-shaped, have thin walls that
stain weakly blue in the
potassium–iodide test, and contain one, two, four or eight
ascospores. The spores themselves are densely —divided by many transverse and longitudinal walls—
ellipsoidal to nearly spherical, often with tiny points at one or both ends. They start colourless and may turn pale yellow-brown when over-mature, and each is surrounded by a very thin, iodine-positive sheath.
Asexual reproduction occurs in dark, partially immersed
pycnidia. These may contain several chambers and release colourless, rod-shaped
conidia produced from short, bottle-shaped cells. No characteristic
secondary metabolites have been detected in the genus using
thin-layer chromatography. ==Species==