Porina decrescens
Description : Thallus epiphloeodal, diffuse to continuous, pale to medium grey-green, matt, smooth to minutely uneven, 20–40 µm thick, ecorticate; prothallus not apparent. Photobiont Trentepohlia; cells 7–16 × 6–13 µm. Perithecia ⅓ immersed and hemispherical to superficial and subglobose, 0.17–0.3 mm diam., dull orange-brown to red-brown; apex rounded; ostiole inconspicuous or in a papilla 20–30 µm wide. Involucrellum contiguous with the exciple, sometimes incurved beneath, 23–40 µm thick, containing algae, K−. Exciple 10–15 µm thick, hyaline to pale yellow-brown. Centrum 0.13–0.19 mm wide. Asci elongate-cylindrical or narrowly obclavate, 70–85 × 7–8.5 µm. Ascospores elongate-fusiform to subacicular, usually tapering towards the proximal end, (3–)5–7(–9)-septate, 23–46 × 2.5–3.5 µm; perispore not apparent. Pycnidia not seen.
S: Nelson (road to Sand Hills Beach), Canterbury (Mt Herbert Banks Peninsula). On fallen branches and twigs of Pseudowintera colorata (Malcolm & McCarthy 1997: 16). Known also from Tasmania and Victoria (McCarthy & Kantvilas 1993b; Kantvilas et al. 1994; McCarthy 2003c, 2003d, 2006).
Australasian
Illustration : McCarthy & Kantvilas (1993b: 141, fig. 2A, B).
Porina decrescens is characterised by: the corticolous habit; minute, orange-brown perithecia, 0.17–0.3 mm diam.; and elongate, (3–)5–7(–9)-septate ascospores, 23–46 × 2.5–3.5 μm.
