Isidium
An isidium is a vegetative reproductive structure present in some lichens. Isidia are outgrowths of the thallus surface, and are corticated, usually with a columnar structure, and consisting of both fungal hyphae and algal cells. They are fragile structures and may break off and be distributed by wind, animals, and splashing raindrops. In terms of structure, isidia may be described as warty, cylindrical, clavate, scale-like, coralloid, simple, or branched.
Examples of isidiate lichens include members of the genera Parmotrema and Peltigera.
