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interesting (at least for me) Rhizocarpon

  • 26 Apr 2015 5:27 PM
    Message # 3317285

    Request some help with a Rhizocarpon for which I’ve posted some photos. Note two distinct areole types with little transition. What's going on with this? Expected R. geminatum or R. disporum, which are relatively common in my area. Medulla is K+yellow, I+blue. 8 spores/ascus; mature ones hyaline and almost entirely 3-septate, average 30x10µm (not much variation). Closest match I’ve found is R. distinctum, but apothecia are more convex than flat, spores are a bit large, and I don’t get K+red on exciple. Several individuals on a Si rock cobble at arid east end of Columbia River Gorge.

    Last modified: 27 Apr 2015 8:49 AM | Richard Droker
  • 03 May 2015 5:02 PM
    Reply # 3325833 on 3317285
    Bruce McCune (Administrator)

    Richard, one possibility is R. polycarpum, which can be 3-septate, has spores hyaline, and medulla I+blue. There aren't many Rhizocarpon species with medulla I+ blue. There is usually a K+ red pigment in the epithecium of this species, but not always, and the exciple should be K-.


    The dimorphism in the areoles is curious -- I have no ideas about that. I'm assuming that the chemistry is similar between areole types, otherwise it looks like parasitism.


    Bruce


  • 05 May 2015 10:12 AM
    Reply # 3328323 on 3317285

    Thanks Bruce. Looks like R. polycarpum as medulla is I+blue. (Seems unusual that most spores 3-septate.) Small areoles appear I- (posted photo).

    Last modified: 05 May 2015 10:13 AM | Richard Droker

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