Orbilia tenuissima Speg.

Quijada, Luis, Baral, Hans-Otto & Beltrán-Tejera, Esperanza, 2016, A revision of the genus Orbilia in the Canary Islands, Phytotaxa 284 (4), pp. 231-262 : 250

Orbilia tenuissima Speg. , Anal. Soc. cient. argent. 26(1): 59 (1888) ( Fig. 11 )

Apothecia 0.8–1 mm in diam., 0.1–0.2 mm high, scattered, pale yellow (89. p. Y) to light orange yellow (67. l. OY), superficial, disc slightly concave to flat, round, margin distinct and crenulate. Asci †(33)33–40 × 2.4–3.5 μm, cylindric-clavate, 8-spored, spores 2–3-seriate, pars sporifera †18–21 μm; with a short- to long-stalked bifurcate base. Ascospores †(9–)10–11(12.7) × (0.7–)0.8–1 μm; subulate, slightly to medium curved (falcate); SBs partially visible, rod-shaped, †1.3–1.6 × 0.4–0.6 μm. Paraphyses uninflated, cylindric to apically slightly to medium clavate, terminal cell †12.5–19 × 1.5–2 μm, lower cells †8–9.5 × 1–1.4 μm; unbranched at upper septum; trace of cylindric-globose drops observed; exudate over paraphyses 1.5–3 μm thick, cloddy and loosely attached or cap like and firmly attached. Ectal excipulum at base and middle flanks of textura angularis to t. globosa, †(50)93–108 μm thick; at margin and upper flank of t. angularis to t. prismatica, glassy processes on cortical cells (5)9–19 μm long, high-refractive, zonate. Cells of ectal excipulum †(11)13–16(19.5) × (7.5)10–14(17) μm at base and lower flank, wall thickness †0.3–1 μm; †6–8(9.4) × 2.6–3 μm at margin, without visible remnants of SCBs in cortical cells at margin.

Previously reported specimens revised:— SPAIN. Canary Islands: Tenerife, Anaga, Monte de las Mercedes, (coordinates and altitude no data), evergreen laurel forest, on wood of Laurus novocanariensis , 12 April 1972, F. E. Eckblad ( CUP-MM 1132!). Erroneously reported as Orbilia auricolor in Korf (1992).

Distribution and ecology:— This species had only been reported in the southern hemisphere in South America ( Paraguay). Growing on petioles of Epipremnum . Occurring in spring ( Spegazzini 1888). In Macaronesia it was once found in the laurel forest on angiosperm wood ( Laurus ) in the same season.

Remarks:— Spegazzini (1888) described O. tenuissima with pale amber-coloured, very thin, smooth apothecia 0.5–1 mm diam., asci 30 × 3–4 μm, and curved, cylindric-fusoid spores 8–11 × 0.5–1 μm. The holotype was re-examined in Baral et al. (in prep.). Orbilia tenuissima was erroneously reported to the Canary Islands as O. auricolor ( Korf 1992) . Until now, no sample found in the Canary Islands corresponds to O. auricolor , but we have found some collections related to O. auricolor .

Orbilia auricolor differs from O. tenuissima in the absence of cell rows at the margin and also in a tendency to larger asci and spores. Delimitation from O. fimicoloides J. Webster & Spooner is problematic, however, since this species concurs with O. tenuissima in the marginal cell rows, but mainly differs in wider ascospores. The Macaronesian collection is somewhat deviating in having rather long asci and also extraordinarily long spores, therefore, its identity is not fully certain.

Figures

FIGURE 11. Morphological features of Orbilia tenuissima. 1. Rehydrated apothecia. 2. Excipular tissues in median section. 3. Glassy exudate at margin and cells rows at flank. 4. Dead asci. 5. Dead paraphyses. 6. Dead ascospores. 500 μm= 1a–c; 50 μm= 2a–b; 10 μm= 3a–b, 4, 5a–b; 5 μm= 6a–b. Mounted in: CR= 3a, 4, 5a–b, 6a; KOH= 2a, 3b, 6b; MLZ= 2b. All photos from CUP-MM 1132.