• Physcia dubia (Hoffm.) Lettau
Click on the image to enlarge it in a new window
Physcia dubia
© Mike Simms
Physcia dubia
Click on map to open large map in new window
(Map updated: 11 August 2009)

Click here to view an interactive map of the Northern Ireland dataset as currently collated by CEDaR.
The map is generated through the NBN Gateway using their Interactive Mapping Tool.


P. dubia is a medium-sized rosette-forming lichen of nutrient-enriched brick wall tops and roofing tiles and other non-calcareous habitats. In habit, it is intermediate between P. caesia and P. tenella (both described elsewhere) with a firmly attached thallus and sorediate, narrowly radiating lobes, slightly splayed at the ends. The K- medulla and lack of marginal cilia should distinguish it from all other lookalikes but P. tribacia which can also have terminal lip-shaped soralia, but usually that species has a paler grey thallus and an overlapping structure. In Ireland, the species has a scattered distribution.

Key characteristics

  • Rosette-forming, dingy-grey with radiating lobes and terminal gritty soredia
  • Soralia: lip-shaped; K- medulla, cilia absent around the edges of the thallus; enriched siliceous rock.

Original text submitted by Vince J. Giavarini

 Simms, M. J., (2016). Physcia dubia (Hoffm.) Lettau. [In] LichenIreland. Accessed on 2018-07-22.