• Placidium rufescens (Ach.) A. Massal. (1855)
Placidium rufescens
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(Map updated: 11 August 2009)

Formerly in Catapyrenium, the thallus of this species consists of heaps of large, leathery, overlapping, pale to dark brown, crowded squamules, some to 10mm diam. The edges of the squamules are dotted with pycnidia (containing the conidia). It grows on dry calcareous rocks and soil. P. lachneum has narrower spores (6-8ųm against 7.5-9.5ųm) and larger conidia (5-7ųm long compared with 3-5ųm in P. rufescens). In Ireland, it is known from the west coast of Counties Mayo and Sligo.

Key characteristics

  • Large leathery brown to dark red-brown squamules low down on limestone rock ledges, soil or sand; spores broad, conidia large
  • On dry, calcareous rocks and rocks protruding through blown sand.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Placidium rufescens (Ach.) A. Massal. (1855). [In] LichenIreland. Accessed on 2019-08-25.