Polycoccum Saut. ex Körb.
Type : * Polycoccum sauteri Körb. [= * Polycoccum trypethelioides (Th.Fr.) R.Sant.]
Description : Lichenicolous, mycelium immersed in thallus of host, subhyaline to pale-brown. Ascomata perithecia, arising singly, immersed with only the ostiole visible, to erumpent, the upper ½ to ⅔ exposed when mature, subglobose to obpyriform, dark-brown to black, ostiolate, neck not extended and scarcely distinguishable from the ascomatal wall; wall even in thickness or somewhat broader close to the ostiole, composed of 3–6 layers of polyhedral, pseudoparenchymatous cells, radially compressed in vertical section, roughly isodiametric in surface view, forming a textura angularis; outer layers of cells with ±evenly thickened walls brown to dark-brown and continuing below centrum; inner layers less intensely pigmented to hyaline and thin-walled. Hamathecium a branched and anastomosing net of thin and regularly septate narrow hyphal filaments, probably trabeculate pseudoparaphyses (paraphysoids?); periphyses absent; hymenial gelatine I+ blue or violet or I−. Asci arising from base of ascomatal cavity, subcylindrical to elongate-clavate, short-stalked, thick-walled with two functional layers (bitunicate) and a small internal apical beak, annulus absent, discharge fissitunicate, 2- to 8-spored. Ascospores irregularly monostichous to irregularly distichous, ellipsoidal, 1(–2)-septate, cells ±equal in size, or the upper cell larger and broader, apices generally rounded or rarely slightly attenuated, somewhat constricted at septum, brown to dark-brown before release from asci, walls rather thin, smooth to delicately or coarsely verruculose, without a perispore. Anamorph unknown.
Key
Polycoccum includes lichenicolous fungi with dark, perithecioid ascomata, a pseudoparenchymatous exciple comprised of dark, angular, polyhedral cells, fissitunicate asci with brown, 1-septate ascospores, and persistent, branched and anastomosing interascal filaments. Species form commensalistic symbioses with their host lichens, and often produce characteristic, gall-like structures on the host thallus. Most appear to be confined to a single host lichen or to a group of related species (Atienza at al. 2003). Thirty-five species are currently accepted (Hawksworth 1975; Diederich 1986; Hawksworth & Diederich 1988; Alstrup & Hawksworth 1990; Matzer 1996; Navarro-Rosinés & Roux 1998; Váczi & Hawksworth 2001; Atienza at al. 2003; Calatayud 2004), mainly associated with saxicolous or terricolous lichen hosts. Matzer (1996: 142–145) described two new species on obligately foliicolous host lichens. The genus is currently referred to the family Dacampiaceae (Lawrey & Diederich 2003; Hawksworth 2003; Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005). The biology of lichenicolous Dacampiaceae was examined by Rîos & Grube (2000) who report that the species are primarily mycoparasitic. Six species are presently recorded from New Zealand, though further species may be expected, especially as parasites of Placopsis.
[An additional New Zealand species, possibly referable to Polycoccum, is recorded in the literature as:
*Polycoccum stictaria (Linds.) D.J.Galloway, N. Z. J. Bot. 42 : 117 (2004).
≡ * Microthelia stictaria Linds., Trans. Roy. Soc. Edinb. 25 (2): 541 (1869).
≡ * Didymosphaeria stictaria (Linds.) Sacc. & Trotter in P.A.Saccardo, Syll. Fung. 22 : 17 (1913).
Hawksworth & Diederich (1988: 310) state: "This species, described on a Pseudocyphellaria species from Campbell Island, was reported to have 1-septate, brown verruculose ascospores produced in 8-spored asci in a centrum turning 'deep violet' in iodine; no dimensions were given. The type material could not be located (Hawksworth 1985a: 166) and no information as to the presence or absence of hamathecial tissues was given. This could represent a further species of Polycoccum but must be excluded until the holotype or other material is discovered".
Lauder Lindsay wrote of Microthelia stictaria : "Parasitic on thallus of Sticta Freycinetii Del., Campbell's Island. Dr Hooker, Antarctic Expedition sub-nom. S. scrobiculata). The conceptacles of the parasite are small, black, and superficial, easily detached. Asci 8-spored, small, subsaccate, deep violet with iodine. This is, at least, an unusual reaction if the plant is a fungus; while it does not appear to possess other characters of a lichen! Sporidia brown, soleiform (1-septate), resembling those of M. rugulosaria, but much smaller." (Lindsay 1866b: 541)].
