• Placynthium tremniacum (A.Massal.) Jatta
Placynthium tremniacum
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Like P. nigrum but thallus often white pruinose, very small (<3cm diam.) and composed of coralloid granules (not squamules). Prothallus poorly developed at the base of the crust; spores persistently one-septate. It grows on damp, shaded hard limestones. In Ireland, the species is known only from Clare.

Key characteristics

  • Like P. nigrum but thallus smaller, more granular in composition and often with a whitish frosting
  • On hard limestone in damp, shady places.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Placynthium tremniacum (A.Massal.) Jatta. [In] LichenIreland. Accessed on 2018-08-16.