Observation 211141: Arthonia spadicea Leighton

When: 2015-07-18

Collection location: Mata do Bussaco, Aveiro, Portugal [Click for map]

Who: zaca

No specimen available

Growing on bark.


Microscopy: Sections;
Microscopy: Asci and spores (x1000).

Proposed Names

58% (1)
Recognized by sight
87% (1)
Eye3 Eyes3
Used references: British Flora
Based on microscopic features

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Microscopy added.
By: zaca
2015-07-23 15:12:08 MST (-0700)

According to the British Flora, among the non-lichenicolous species of Arthonia growing on bark only two have 1-septate spores:
- A. dydima with spores dimensions of (12-)14-17 × 4.7-7 µm;
- A. spadicea with spores dimensions of 7-11 × 3-4 µm.
I obtained the following values for the spores of my specimen:
8 – 9.5 × 3.1 – 4 µm [Q = 2.12 – 2.7 ; N = 7; Me = 8.6 × 3.6 µm ; Qe = 2.4].
On the other hand the macro features given there for A. spadicea fit very well in my specimen, in particular the green-tinged thallus, the rounded and flat to slightly convex apothecia, red-brown to brown-black coloured. Thus I believe that A. spadicea is the species of my specimen.
Because the spores are so small, they are difficult to see at the usual scope magnification (400). Consequently, I made an attempt to present photos with magnification of 1000. Since in my scope there is a considerable loss of quality at higher magnification the photo with the asci and spores is of bad quality, and I apologise for that; Nevertheless, the form of the spores and asci are better understood at 1000X than at 400X and thus I decided to present it.

Created: 2015-07-22 14:08:37 MST (-0700)
Last modified: 2015-07-23 15:14:12 MST (-0700)
Viewed: 35 times, last viewed: 2017-11-04 04:21:54 MST (-0700)
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