The types of lichen
The "body" of a lichen is termed the thallus, and its general shape enables us to group lichens into four broad categories.
Foliose lichens have a flat, leaf-like structure
Fruticose lichens have an erect or pendulous, bushy structure
Squamulose lichens have a thallus consisting of minute, scale-like squamules
Crustose lichens produce a flat crust on or beneath rock or tree surfaces
