Flora of New Zealand Series

Type : * Stigmidium schaereri (A.Massal.) Trevis. [= * Sphaeria schaereri A.Massal.]

Description : Lichenicolous, immersed in thallus or ascomata of host. Ascomata perithecia or pseudothecia, erumpent or sessile, ±immersed to prominent, black, scattered or crowded, globose, subglobose or ellipsoidal in section. Peridium of isodiametric to tangentially elongated cells, brown, paler below than above, with an amorphous or minutely granular pigment in cell walls. Periphyses indistinct or distinct, short. Hamathecium deliquescent, usually lacking in mature ascomata. Asci fissitunicate, saccate, ellipsoidal or cylindrical with a short stalk, 8-spored; endoascus strongly thickened in upper parts of immature asci. Ascospores hyaline, ellipsoidal with rounded ends, 1-septate (to 3-septate), not or very slightly constricted at septa, walls smooth to rarely finely scabrid, without a gelatinous sheath. All parts of ascomata I−, KI−.

Stigmidium, included in the Mycosphaerellaceae (Hawksworth 2003; Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005), is a genus of c. 52 species of lichenicolous fungi with small, perithecioid ascomata; functionally fissitunicate asci; mostly 1-septate, colourless ascospores (but also 3-septate and/or pale brown ascospores in some taxa); and the absence or sparse development of hamathecial elements (Calatayud & Triebel 2001). Although discussed in a variety of accounts of lichenicolous fungi (Santesson 1960; Hawksworth 1975, 1986b; Triebel 1989; Alstrup & Hawksworth 1990; Matzer & Hafellner 1990; Triebel et al. 1991; Kondratyuk & Galloway 1994; Roux & Triebel 1994, 2005; Roux et al. 1995, Matzer 1996; Calatayud & Triebel 1999, 2001, 2003; Triebel & Scholz 2001; Hafellner et al. 2002; Etayo 2002; Diederich 2003; Etayo & Osorio 2004; Santesson et al. 2004; Triebel & Cáceres 2004), it is much in need of a modern revision, as its taxonomy is partly based "merely on occurrences on different hosts" (Alstrup & Hawksworth 1990: 66). As currently defined (see above), Stigmidium remains heterogeneous. Presently, five species are known from New Zealand, but the genus is still very imperfectly known and collected here. Additional species should be looked for on species of Caloplaca and Lecanora.