Flora of New Zealand Series

Type : * Hemigrapha asteriscus (Müll.Arg.) D.Hawksw. [= * Melanographa asteriscus Müll.Arg.]

Description : Lichenicolous. Ascomata thyriothecia [an inverted, flattened ascoma, having the wall ±radial in structure and lacking a basal plate (Hawksworth et al. 1995: 457)] black, superficial, flat, rounded, stellate, elongate, simple or branched, sometimes confluent; upper ascomatal wall comprising a single later of ±parallel, radiating rows of dark-brown, short-rectangular cells, continuous above hymenium; basal plate absent, although the zone between the host epicortex and the hymenium may become brownish; ostiole central, often inconspicuous, best seen on microscopic examination of whole ascoma. Ascomatal wall dark reddish brown, K+ dark olivaceous brown, N–, pigment intracellular; wall often breaking by irregular cracks around ostiole, partially exposing hymenium. Hymenium I−. Hamathecium of sparingly branched, occasionally anastomosing paraphysoids, at maturity becoming free at top and at length disappearing; periphysoid-like cells arising from ascomatal wall in some specimens, short and thick, simple to 1-septate, ?functioning as conidiogenous cells. Asci clavate to subglobose, fissitunicate, wall apically thickened, normally with a distinct ocular chamber, laterally thin, I−, (2–)4–8-spored. Ascospores 1–3-septate, constricted at septa, hyaline at first, pale brownish at maturity, smooth-walled, though over-mature spores often granular to verrucose. Perispore absent. Conidiomata pycnothyria [superficial, flattened shield-shaped conidiomata with radiate upper and sometimes lower walls (Hawksworth et al. 1995: 386)], macroscopically indistinguishable from thyriothecia with which they are often intermixed, with upper wall only; conidiophores absent. Conidiogenous cells arising from conidiomatal wall, holoblastic, discrete, determinate, subspherical, ellipsoidal to shortly ampulliform, simple to rarely 1-septate, hyaline, smooth, without proliferations. Conidia hyaline, simple, smooth, base truncate or not, ellipsoidal of two kinds: microconidia – narrowly ellipsoidal to rod-shaped; macroconidia – larger, ellipsoidal.

Hemigrapha is a genus of lichenicolous fungi of wide distribution, included in the family Parmulariaceae (Lawrey & Diederich 2003; Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005) in the order Dothideales and as currently circumscribed comprises four species (Diederich & Wedin 2000). Two species are recorded from New Zealand (Diederich & Wedin 2000; Santesson 2001) where they are commensalistic on species of Nephroma and Peltigera. Still rather poorly collected and understood here, they should be searched for more widely.