Dirinaria leopoldii

Frequently the surface (cortex) of this lichen erodes away to reveal small red patches which separate it from other members of this genus in our area. However, Dirinaria are visually very similar to another common genus (Physcia) of foliose lichens. The former has a black underside without hair-like or root-like structures called rhizines. Edges of the lichen are also quite tightly adhered to the substrate. Most Physcias have white undersides (there are exceptions) and rhizines on the underside are conspicuous.  Margins are generally loose and easily pried back.