cortex (noun, pl. cortices; variant spelling: pl. cortex) – outermost layer of the thallus (and of lecanorine apothecial margins) which, if present, in the true sense consists of compacted hyphae which may appear either fibrous or cellular, sometimes gelatinized; relatively hard and tough, protective in function; used loosely to include superficially similar outer layers; also used sometimes for the wall of a pycnidium. Related terms: eucortex, phenocortex, pseudocortex, cone cortex, epicortex, syncortex, ecorticate. This is:part of thallus surface,part of thallus interior.