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Mystery Bacidia on Elder

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  • March 23, 2025 at 3:20 pm #33018
    SylviaD
    Participant

      Hi,

      Out with the Petersfield group on Woolbeding Common, West Sussex, I took a sample of pink/grey apothecia found on the trunk of an Elder. So far I’ve found the following, but it’s proving a bit of a puzzle.

      Thallus: white, but not very thick or conspicuous

      Apothecia: lecideine, less than 0.5mm, light pink/grey but many with a very distinctive grey ‘margin’ around what I think is the inner part of the thalline margin. Some had some grey speckling. I had just found Bacidia laurocerasi and I felt they had the same ‘shape’ and ‘look’ but without the colour.

      Apothecia section: Virtually devoid of any pigment, except for a slight greenish colour to the epithecium in water

      Hypothecium: colourless, around 45-50um

      Spores: 8 per ascus, needle-shaped, most seemed 3-5 septate, but there were a few with 6-7 septa

      I have attached photos, but the apothecia didn’t take the K/ink stain well at all. Based on microscopy, I thought perhaps Bacidia phacodes, but the apothecia didn’t seem right and probably not the right habitat.

      Anyway, I would appreciate any pointers on what to do next or any suggestions as to what this lichen is. Or have I just missed something really obvious.

      Thank you

      Sylvia

      March 23, 2025 at 10:15 pm #46539
      maxieput901

        Hi Sylvia

        Do you have some measurements for spore length for this Bacidina (?) ? The habitat being elder may suggest Bacidina caerulea of B. friesiana but the colour in K is important for identification and you say yours doesn’t react clearly to K.

        Maxine

        March 24, 2025 at 11:30 am #46540
        SylviaD
        Participant

          Thanks Maxine – I can’t believe I forgot to put in the spore size – it was 35-40 X 1.25-3.0 um

          There was little if any colour change with K, the only thing I noticed was the grey pigment in the exciple went from slightly grey/green to grey/lilac. I did a mount in K and thought the colour looked slightly different, so I then did a mount in water and flushed K through while on the microscope – and there was a change, but not sure I would say a great difference and probably not significant and might well just be my colour perception. I’ve attached a photo of the grey/lilac colour. Overall my general feeling was that not a lot or probably nothing happened with K.

          Thanks for your help, Sylvia

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