Flora of New Zealand Series

Type : Rhytidiella moriformis Zalasky

Description : Thallus absent. Ascomata perithecia erumpent, superficial, hemispherical, very black, usually with a truncate base; apex sulcate, pored. Paraphyses abundant, brown, branched, anastomosed, with a thick gelatinous wall. Asci cylindrical to clavate, bitunicate, 8-spored. Ascospores scolecosporous, hyaline to yellow-brown, septate.

Rhytidiella is a genus of three species (Kirk et al. 2001), tentatively included in the family Cucurbitariaceae (Eriksson et al. 2004; Pennycook & Galloway 2004). Two species, from Canada and Sweden are strong pathogens forming bark cancers on two different species of Populus (Zalasky 1968; Aguirre-Hudson 1991). The third species is a New Zealand endemic formerly included in the lichen genus Leptorhaphis (Galloway 1985a: 254). However in her taxonomic studies on Leptorhaphis and related genera (Aguirre & Hawksworth 1987; Aguirre-Hudson 1991: 167), Dr Begoña Aguirre-Hudson has argued for placing the New Zealand taxon in the fungal genus Rhytidiella, based on similarities in ascomatal wall structure, ascus and ascospore morphology, and hamathecial tissues.