soredium
noun
so·re·di·um
səˈrēdēəm
plural soredia
-dēə
: one of the vegetative gemmae on the surface of the thallus of a lichen consisting of a tuft of hyphae investing a few algal cells or gonidia
called also brood bud, hologonidium
Word History
Etymology
New Latin, irregular from Greek sōros heap + New Latin -idium; akin to Latin tumēre to swell