Orcularia placodiomorphoides (Imshaug) Kalb & Giralt

Kalb, Klaus & Giralt, Mireia, 2011, Orcularia, a segregate from the lichen genera Buellia and Rinodina (Lecanoromycetes, Caliciaceae), Phytotaxa 38, pp. 53-60 : 58

Orcularia placodiomorphoides (Imshaug) Kalb & Giralt , comb. nov. Mycobank MB 563562

Buellia placodiomorphoides Imshaug , Farlowia: 499 (1955). Type:— Jamaica. Summit of Caterines Peak , 5000 ft., Imshaug 13343 (FH!).

Thallus corticolous, whitish-grey to ochraceous, thin, composed of scattered, small verrucae. Prothallus present, blackish. Apothecia small, 0.3-0.5 mm diam., sessile; disc black, flat, not pruinose; proper margin black, entire, prominent and persistent. Proper exciple (40–)50–60(–70) µm thick, inner part colourless including several clusters of crystals and many oil droplets, outer part brown. Hypothecium 60–80 µm high, brown. Hymenium (80–) 100–120 µm high, not inspersed. Epihymenium brownish, covered by a coarsely, colourless epipsamma dissolving in KOH. Paraphyses 1.8–2.0 µm thick, end cells 2–3(–4) µm broad, with a brown cap. Asci 8-spored. Ascospores 1-septate, (20–)23–26(–28) × (9–)10–11(–12) µm, olive, later pale brown, spore wall smooth; at first lumina only apical, connected by a long isthmus, later with two additional septal lumina. Pycnidia black, 50–60 µm diam., conidia filiform, 15–27 × 1 µm. Chemistry: Spot test (thallus): KOH+ yellow turning reddish sometimes followed by the typical formation of the acicular crystals characteristic for norstictic acid.

Notes:—This species, known only from the type collection, was described by Imshaug (1955). It is similar to O. placodiomorpha , but is distinguished by somewhat larger apothecia (0.3–0.5 mm diam. versus 0.4 mm), and especially by the larger ascospores (20–28 × 9–12 µm). Furthermore, in O. placodiomorphoides the epihymenium is covered by an episamma; the proper exciple is thicker (up to 70 µm); and the thallus contains crystals of a secondary lichen substance reacting K+ yellow-red.