Collection location: Estádio Nacional, Oeiras, Portugal [Click for map]
Some features of this specimen:
- Growing on bark;
- Thallus: dark, greyish/brownish, wrinkly;
- Apothecia: with a very generous white rim that almost covers the disc, disc dark-orange/red;
- Chemical reactions on thallus: C-, K- to K+ very pale yellow, KC + weak yelow;
- Microscopy: asci 8-spored (I presume), spores dimensions: 26.5 – 29.5 × 11.5 – 13.5 µm ; Qe = 2.3 (N=20).
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sum(score * weight) /
(total weight + 1)
this is very different from Pertusaria hymenea, a common species here that I already find several times. Macroscopically, the thallus of Pertusaria hymenea is lighter and more wrinkled, the apothecia are more dense, and the rims of apothecia not so developed. Microscopically, the spores are much longer. Based on there size and shape, I believe this one is Ochrolechia.
If the spores weren’t so tiny, I would suggest Pertusaria hymenea which matches pretty well otherwise. But (mature) spores should be at least twice as big as what you observed! None of the Ochrolechia in the British Flora even comes remotely close. I suppose we could consider Lecanora in a pinch… but nothing looks promising, not with such thick rims.
I interpret the spot tests as indicating presence of a xanthone. I would expect C+ orange, too, but it might be too weak to see. KC will bring out weak C tests. UV should also verify presence of a xanthone.
There are a bunch of species around P. hymenea in Sipman’s key, many with a xanthone. Maybe you’ve got a new one!