Definitions for "Crustose"
a lichen growth form; thalli crust-like, growing in direct contact or buried within the substrate; lacking a lower surface layer and rhizines. see Fig. 9, p. 14.
A crust-like growth form that is closely attached to the substrate, like paint, generally adhering by all of the lower surface and lacking a lower cortex and rhizines.
(of lichens) having a thin crusty thallus that adheres closely to the surface on which it is growing; "crutose lichens"