Darkera abietis H.S. Whitney, J. Reid & Piroz., Can. J. Bot. 53(24): 3052 (1975)
= Tiarosporella abietis H.S. Whitney, J. Reid & Piroz., Can. J. Bot. 53(24): 3055 (1975)
Foliicolous, occurring on needles of Abies balsamea. Sexual morph: Apothecia 300–550 µm diam., 100–500 µm high, black, solitary to gregarious, or confluent, subhypodermal, immersed to semi-immersed, then becoming erumpent, ellipsoid to elongate, unilocular, glabrous, ostiole absent, dehiscence of the apothecia by an irregular split in the apical wall. Peridium 20–40 µm wide, composed an outer pseudoparenchyma of compact textura angularis with thick-walled and brown to pale brwon cells in the basal part, passing into brown to dark brown cells of textura angularis in the lateral part. Hamathecium consisting of paraphyses and asci. Paraphyses 40–90 × 2–4 µm, hyaline, numerous, slender, with occasionally slightly swollen base and obtuse apex, becoming free at the upper end only as the apothecium matures, branched at base, anastomosing, septate, often constrict at septa. Asci 40–90 × 10–25 µm ( = 66 × 18.5 µm; n = 30), bitunicate, fussitunicate, with an ocular chamber, 8-spored, clavate to broadly clavate, with blunt and rounded apex, sessile or sometimes with broadly short-cylindrical pedicel, lacking pore structure, ascospores released by apical wall irregularly rupturing in the middle part. Ascospores 19–28 × 7–18 µm ( = 23 × 12 µm; n = 30), hyaline to pale brown, uniseriate or biseriate, or irregularly arranged, rounded or broadly ellipsoid, sometimes slightly tapering with rounded ends, unicellular, smooth-walled. Asexual morph: Coelomycetous. Conidiomata 200–300 µm diam., 140–300 µm high, pale brown to brown, pycnidial, mostly epiphyllous, sometimes amphigenous, solitary to gregarious, subepidermal, deeply immersed, raising the epidermis into brown swellings, then piercing it by a lateral neck, globose to subglobose, unilocular, glabrous. Ostiole single, cylindrical to subcylindrical, laterally located. Conidiomatal wall 20–70 µm wide, composed of thick-walled, pale brown to hyaline cells of textura angularis in the basal part, becoming relatively thick-walled, brown to pale brown cell of compact textura angularis to textura porrecta or textura intricata in the upper and lateral part. Conidiophores arising from the innermost layers of conidiomata, reduced to conidiogenous cells, or occasionally present, hyaline, subcylindrical, unbranched, septate, constricted at septa. Conidiogenous cells 7–20 × 3–4 µm, hyaline, enteroblastic, cylindrical to conical, determined, smooth-walled, without proliferation. Conidia 39–51 × 6–10 µm ( = 46 × 7.5 µm; n = 30), hyaline, subcylindrical to subclavate, with a rounded apex and a narrow, truncate base bearing minute marginal frills, straight or slightly curved, unicellular, smooth-walled, guttulate, bearing an irregular, widely flared, mucoid, apical appendage.
Material examined: Canada, Ontario, Geraldton District, Rod Lack, on needles of Abies balsamea (Pinaceae), 22 July 1961, Jansons, Griffin & Lynn (DAOM 145406 a & b, holotype); Alberta, Slave Lake, Smith, 2 mile N. W. of Lawrence L. campground, on needles of A. balsamea, 22 May 1968, C. Layton (DAOM 145416, type).
Darkera abietis (DAOM 145406 a & b, holotype) a, b Herbarium package and specimen. c, d Appearance of black ascomata on the host. e, h Vertical section of conidiomata. f Hamathecium with asci and paraphyses. g Section of peridium. i Paraphyses. j–n Asci. o–s Ascospores. Scale bars c = 500 µm, d, e, h = 200 µm, f = 50 µm, g, i, j–n = 20 µm, o–s = 10 µm.