• Porpidia speirea (Ach.) Kremp.
Porpidia speirea
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(Map updated: 11 August 2009)

This chalky-white, non-sorediate, non-isidiate lichen of basic rocks can only be confused with Rhizocarpon umbilicatum (medulla = K+ yellow, Pd+ orange) when in this environment. On acid rock, similar coloured Porpidia crusts usually turn out to be P. cinereoatra (described elsewhere). P. speirea has an Iodine + violet medulla, confluentic acid and immersed discs. In Ireland, the species is thinly scattered.

Key characteristics

  • Thallus chalk-white, discs immersed; medulla K-, Pd-
  • Always on hard, basic rock.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Porpidia speirea (Ach.) Kremp.. [In] LichenIreland. Accessed on 2018-09-23.