Phacidiales » Phacidiaceae » Darkera

Darkera parca

Darkera parca H.S. Whitney, J. Reid & Piroz., Canadian Journal of Botany 53: 3053 (1975)

= Tiarosporella parca (Berk. & Broome) H.S. Whitney, J. Reid & Piroz., Can. J. Bot. 53(24): 3055 (1975)


Foliicolous, occurring on needles of Picea glauca. Sexual morph: Apothecia 200300 µm diam., 100150 µm high, brown to dark brown, acervulus, subhypodermal, initially immersed, ultimately becoming erumpent, solitary to gregarious, ellipsoid to elongate, unilocular, glabrous, ostiole absent, dehiscence by a lateral overlying host tissue. Peridium 1040 µm wide, composed of an outer pseudoparenchyma of compact textura angularis with thick-walled and pale brown to hyaline cells in the basal part, passing into thick-walled, brown to dark brown cells of textura angularis in the lateral and upper part. Hamathecium consisting of paraphyses and asci. Paraphyses 50–90 × 24 µm, hyaline, numerous, slender, with occasionally slightly swollen apex, septate, branched, enveloped by a thin mucilaginous sheath. Asci 70–120 × 1724 µm ( = 96 × 20 µm; n = 20), bitunicate, with an ocular chamber, 8-spored, clavate to broadly clavate, with rounded apex, sessile or sometimes with short pedicel, lacking pore structure, releasing ascospores by apical wall irregularly rupturing. Ascospores 20–34 × 913 µm ( = 27 × 11 µm; n = 30), pale brown to olivaceous-brown, uniseriate or uniseriate at base, then becoming biseriate at upper half of asci, or irregularly arranged, subreniform or allantoid, or elliptical to broadly elliptical and slightly tapering with rounded ends, unicellular, smooth-walled at beginning, late with bright, crack-like decorations at ascospore surface. Asexual morph: Coelomycetous. Conidiomata 200250 µm diam., 60120 µm high, amphigenous, pycnidial, solitary to gregarious, hypophyllous in origin, raising the epidermis into dark brown swellings, then piercing the epidermis and forming an ostiole, deeply immersed, ellipsoidal, unilocular, glabrous. Ostiole single, cylindrical, laterally located. Conidiomatal wall 1030 µm wide, composed of thick-walled, hyaline cells of textura porrecta to textura intricata in the basal part, passing into thick-walled, brown to pale brown cell of textura anularis in the upper part and ostiolar region. Conidiophores reduced to conidiogenous cells, or occasionally present, hyaline, subcylindrical, branched, septate, arising from the innermost layers of conidiomata. Conidiogenous cells 715 × 35 µm, hyaline, enteroblastic, annellidic, cylindrical to lageniform, occasionally conical, discrete or sometimes integrated, smooth-walled, with 1–3 percurrent proliferations. Conidia 37–54 × 814 µm ( = 42 × 11 µm; n = 50), hyaline, subcylindrical, sometimes bulging in the middle part, with rounded apex, and sometimes narrow, truncate base bearing marginal frills, straight or slightly curved, unicellular, smooth-walled, bearing an irregular, mucilaginous appendage which initially envelopes upper half, eventually becoming an everted mucilaginous sheath at apex.


Material examined: Canada, Alberta, Two Lakes Rd., 68 mile S.W. of Wembley, on needles of Picea glauca (Moench) Voss (Pinaceae), 4 July 1965 J. Petty & G.J. Smith (DAOM 145413, holotype), (DAOM 145413b, holotype of asexual morph).



Darkera parca (DAOM 145413, holotype) a, b Herbarium package and specimen. c–d Appearance of brown to dark brown conidiomata on the host. e, f Vertical section of conidiomata. g, h Section of peridium. i–k Asci. l Paraphyses. m–n Asci apex with ascospores. o–q Ascospores. Scale bars c = 1000 µm, d = 500 µm, ef = 100 µm, g = 50 µm, h = 20 µm, i–q = 10 µm.