Pyxine Fr.
Thallus heteromerous, foliose, dorsiventral, rosette-forming to irregularly spreading, closely attached. Upper surface paraplectenchymatous, of anticlinal hyphae, white, greyish-green, grey to brownish-grey, pruina, pseudocyphellae, soredia and isidia present or absent. Medulla white, pale straw-coloured to deep ochraceous-orange (pigments K+; purple). Photobiont green ? Trebouxia. Lower surface corticate, of longitudinally arranged hyphae forming a prosoplectenchymatous tissue, dark brown or black, rhizinate. Rhizines black, simple, often with an anchoring, squarrose tuft at tip. Apothecia lecanorine, appearing lecideine, thalline exciple often not well-developed. Epithecium and tips of paraphyses K+ purple. Hypothecium brown. Asci of Physcia -type, 8-spored. Ascospores 1-septate, brown, thick-walled of Physcia - or Mischoblastia -type.
Pyxine, included in the family Physciaceae [Swinscow and Krog Norw. J. Bot. 22: 43-68 (1975); Hafellner et al., Herzogia 5: 66 (1979)] contains c. 35 mainly tropical species. It is distinguished from other members of the Physciaceae by the lecideine appearance of the apothecia, the K+ purple reaction of the epithecium, a dark brown hypothecium, often lichexanthone (UV+ citrine yellow) in the upper cortex, and a black lower surface. One species is presently known from northern New Zealand.
