Some features of this specimen:
- Growing on the bark of Quercus coccifera;
- Thallus greyish, continuous;
- Apothecia very small (up to 0.5 mm), irregularly rounded, vinaceous coloured;
- Epithecium and hypothecium red-brown, hymenium concolor but paler;
- Spores similar in form to those of A. cinnabarina (i.e. oblong-ovoid with terminal cell enlarged), but smaller, 3-4 septate, with the following average dimensions: Me = 20.5 × 7.5 µm ; Qe = 2.8.
Following the key of the British Flora (see ref.) I end up with Arthonia ilicinella.
The name refers to a species close to A. ilicina, which also has spores similar to A. cinnabarina, but with shorter apothecia and spores.
My only concern about the proposed name is the color of apothecia, which seems to be red-brown or vinaceous while A. ilicinella has black apothecia. However, the dried specimen has indeed brown apothecia and the descriptions given in the reference are all based on dried specimens.
Some other species are closer to my specimen, in respect to the colour of apothecia, like A. vinacea or A. stellaris, but the former has much shorter spores while the latter has stellate apothecia and the old spores are distinctly warted. In my specimen, the old spores are pale brown and at most faintly warted.
In the attached photos from microscopy the bluish tone is due to a drop of melzer that was added to the slide for better observation of the spores, Which are hialine at first becoming brown at maturity.
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Created: 2014-09-02 16:39:17 AST (-0400)
Last modified: 2016-05-29 15:44:43 AST (-0400)
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