Fungi Outer Hebrides

  • Rhizocarpon reductum
  • Lecanora pulicaris
  • Ochrolechia parella
  • Verrucaria striatula
  • Pertusaria albescens
  • Caloplaca thallincola

Crustose and Placodioid Lichens

In crustose lichens the thallus closely adheres to the substrate to form a crust. The fungal hyphae are able to penetrate the surface of the substrate and therefore, the lichen can not be removed from the substrate in one piece. In cases where the thallus is deeply immersed in the substrate the presence of reproductive bodies or variations in colour are the only indication that a lichen is present.
The crust can be smooth and entire, cracked or divided into patches (areoles), or with a rough or warty surface. The thallus may be surrounded by a border of fungal tissue, the prothallus, which is often particularly noticeable in a lichen mosaic where two lichens meet. In placodiod lichens the edge of the thallus is defined by the presence of long radiating lobes and the absence of a prothallus.

Crustose and Placodioid Species