Cephalodia are vegetative structures peculiar to lichens found on the upper surface of the thallus. They are small, dark-coloured gall-like swellings. They contain the same fungal hyphae as in the thallus but the algal component always differs.
Isidia are small, finger-like or conical outgrowths developed on the upper surface of the thallus and are meant for increasing the surface area. Isidia develop into new plants when they detach. Isidia have the same fungal and algal components as those of the thallus. The isidia vary in form in different species of lichens. They maybe rod-shaped (Parmelia), cigar-shaped (Usnea), corolloid or coral-like (Peltigera) etc.