Pronectria xanthoriae  

Ascomata perithecia, 140-250 (-400) µm diam. and 150-300 (-400) µm high, pyriform, immersed in the apothecia and sometimes the thallus of the lichen, scattered or in groups of up to six; apical papilla truncate, 60-120 µm high and 200 µm diam., periphysate, raising the surface of the apothecia in rounded mounds or as cylindrical projections with a translucent dark orange centre, bright orange, not changing colour in KOH. Peridium 15-20 µm thick, composed of several layers of thin-walled elongate cells 9-12 x 2-4 µm in size. Interascal tissue absent. Asci (50-) 64-80 x 6-13 µm, clavate, thin-walled, the apex truncate with an inconspicuous apical ring that does not blue in iodine, 8-spored. Ascospores biseriate in the middle, uniseriate above and below, 17-24 x 4-5 µm, ellipsoidal-fusiform, 1-septate, hyaline, verruculose, with one to three guttules per cell.

Description adapted from Lowen & Diederich (1990).