Heppia

Heppia is a genus of olive, brownish, gray, or blackish squamulose, crustose, or peltate lichens. It is in the family Heppiaceae. It grows on rock or soil in arid sites around the world, in habitats similar to those favored by Peltula, which is similar but has a different cyanobacterium as the photobiont. It lacks a medulla that is separate from the photobiont layer. It is a cyanolichen with the photobiont cyanobacterium being Syctonema (or Syctonema-like). The lower surface is paler than upper surface, and has numerous rhizoidal hyphae attaching it to the substrate. The fruiting structures (ascomata) are apothecias immersed in the thallus with red to red-brown urn shaped (urceolate) to flat or slightly convex discs. An exciple may or may not be present.