Hi all, first post.

Just started looking at Ascos, and this is my third attempt to ID one with microscopy. I would appreciate any feedback and thanks for looking. Unfortunately I couldn't upload the individual photos without an error.

Several tiny, bright-orange, discomycetous ascomata on wood, collected accidentally on a sample with a suspected yellow Calycina sp. (microscopy not done).

Looks like Orbiliaceae, and I have tried to use the 2020 monograph by Baral et al. Lots of micromorphology to (mis)interpret, so I have not cropped and combined the microphotos.

Current Idea:
· Genus Orbilia: Macromorphology, croziers -, anchoring hyphae VBs -, singular SBs.
· Subgenus Orbilia, section Orbilia: VBs +, ascus base shapes, paraphyses, SB shape, (asco)spore shape.
· Series Orbilia: Spore size and shape, SB shape, paraphyse apices, glassy processes -.
· Similarities to O. tremulae and O. eucalypti group (part of Key A in Baral et al.), but hard to be confident with variable species and my inexperienced observations.

Storage and prep:
Kept attached to wood sample in the fridge in a water-tight container for 2-3 weeks. Ascomata visibly shrunken and darker, appeared to change more than ascomata of other species in the same container (desiccation sensitive?). Two slides prepared with different ascoma, 'rehydrated' for ~30 seconds in tap water on a slide before applying cover slip.

Description:

Habitat and conditions: Hygric wood (decorticated part), branch from deciduous tree, on the floor in mixed deciduous woodland, southern England, a few weeks ago after rain.

Ascomata: Diameter <= 0.5 mm, bright orange, translucent, broadly sessile, growing laterally if in crevices, relatively thick, margin slightly raised and maybe more lobate in maturity, no noticeable hairs or glassy processes, texture slightly rough.

Asci: five measured 34 - 41.5 × 3.3 - 3.5 µm, 8-spored, simple septa, base often furcate and variable (some H-shape), thin-walled, apex hemispherical in profile and noticeably truncate in forward view (including dead asci), no distinct apical chamber, some presumably living asci have more space around spores, several spores seem reversely oriented, but no clear pattern to positions and orientation identified.

Ascospores: Ovoid-elipsoid, aseptate, no noticeable tail or curvature, several small globose VBs, lots look bi-guttulate, some seem to be living; spore body singular, globose, seems apically attached but no filum seen, appearing as clear area in presumably dead spores, not clearly identified in some spores.
· Outside asci: 10 measured, 4 - 5 x 2.1 - 2.3 µm, Q = 1.8 – 2.4, some may be dead.
· Inside asci: 15 measured, (3.4) 3.7 - 4.8 (5) × 2.1 - 2.8 µm, Q = 1.4 - 2.3.

Exudate: Granular, yellow, with small crystals (SCBs?), relatively thin and easily disturbed, mature asci emerging, no gelatinous matrix.

Paraphyses: Mixture of uninflated (~1.7 µm) and medium to strongly clavate/capitate (~2.7-3.5 µm) apices, +/- symmetric, multi-septate, some apical cells appear longer, often several smallish globose VBs in each cell, some capitate apices with a larger VB, branching below the apical septa, not sure which VBs could be SCBs, occasionally exudate remaining.

Anchoring hyphae: ~(3) 4 - 5 µm wide with septa ~3 - 5 µm apart, no branching seen, brown walls, clear contents.

No anamorphic structures identified.