POTRIPHILA-NAVICULARIS GEN ET SP-NOV (OSTROPALES, ASCOMYCETES), A BIPOLAR DISPERSE PARASITE ON POLYTRICHUM-ALPINUM

Potriphila naviculoris Dobbeler (Odontotremataceae, Ostropales), a new genus and species of bryophilous ascomycetes with bipolar distributio n, is described in detail and illustrations are included. The biotroph ic parasite frequently infects the widespread Polytrichum alpinum (Mus ci). Its reduced and laterally compressed fruitbodies are completely i mmersed between the longitudinal leaf lamellae of the host. Important taxonomic characteristics are immersed, hemiangiocarpic, apothecioid a scocarps which open by irregular fissures to expose the uncoloured hym enium; carbonized excipulum of small-celled textura intricata without an internal periphysoidal layer; filiform, not anastomosing, above une xpanded paraphyses; unitunicate, apically slightly thickened, 8-spored asci with amyloid walls; 1-septate, narrowly ellipsoidal ascospores; fine intercellular and epicellular hyphae with coiled haustoria within the leaf-hairs; ostiolate pycnidia of the same excipular-type as the ascocarps with I-celled conidia; systemic infection. Possible relation ships exist with the odontotremoid bryophilous genus Bryodiscus, which comprises necrotrophic parasites. Problems concerning the mycelial ch aracteristics, host preference, relationship between teleomorph and an amorph, adaptations to the manner of life, geographical distribution a nd the systematic position are discussed. A list of the fungi hitherto known from Polytrichum alpinum is included.