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Porina rosei or similar

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  • September 29, 2026 at 8:50 am #70914
    chriscant
    Participant

      On the Cumbria Lichen and Bryophyte Group meet at Thorneythwaite at the south end of Borrowdale, Lake District, Cumbria, a week or so ago there was a nice wych elm with Gyalecta truncigena, Bryobilimbia sanguineoatra, Mycobilimbia sphaeroides, Opegrapha vermicellifera and some jellies. This yellow/orange isidiate lichen was on the north facing side of the elm. It appears coralloid isidiate possibly made up of joined granules, with the clumps of isidia almost forming a continuous sward in places, with the height of the isidia up to approx 0.2mm. The isidia appear to have colourless cells on the outside. The algae appear consistently orange. The width of the isidia vary between 25 and 40μm.

      We’ve been considering Porina rosei, Coenogonium nimisii and Porina hibernica. There’s one Cumbria record of P rosei from nearby in 2025. There’s a 1990 record of P hibernica very close by.

      Do you think any of these match? Or something else entirely?

      Thanks, Chris

      Thallus

      Isidia with colourless cells on outside

      Another isidium

      October 9, 2026 at 7:51 am #70932
      Neil Sanderson
      Senior Moderator

        Chris

        Looks good for Porina rosei, definitely with a clear cortex, so not Porina hibernica, the cortex has projecting cells, so not Coenogonium nimisii which has a smooth outline and not projecting enough to be Porina atlantica. 40 µm is a bit wide for a well grown Porina rosei isidia but there is an issue in that the isidia start stubby and wide then thin as they grow up. The dense but clumped look of the isidia is what would be expected as well. The nearby record of Porina hibernica is interesting as there was a lot of past confusion and not all old Porina hibernica records are easy to check. There is a Brian Coppins specimen of Porina hibernica from Elm in Borrowdale that has been checked, which could be the one you refer to, but this is the northern most confirmed record for Porina hibernica I am aware of; it would be good to see a recent specimens from Scotland (the most recent dot from Glen Coe seems to have been Porina collina, it was on a upland boulder).

        Neil

        October 13, 2026 at 8:29 am #70952
        chriscant
        Participant

          Thanks Neil – useful to know what to look for.
          The 2025 Seathwaite record of Porina rosei is from Oliver Moore, Dave Lamacraft et al so likely to be right.
          The 1990 Porina hibernica record is indeed from Brian. Two records are showing but they are almost certainly the same one duplicated.
          Ta Chris

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