Flora of New Zealand Series

Thallus crustose, epiphloeodal or hypophloeodal, cortex when present loosely organised to dense, smooth to roughened or cracked, rarely splitting and exfoliating, without a prothallus, medulla usually evenly distributed in a layer 2-4 cells thick (10-30 µm). Apothecia somewhat immersed, to raised or strongly emergent, the thalline wall incurved to erect to recurved. Exciple free (detached) or rarely fused (attached), the inner face covered with short periphysoids. Pore often broad and gaping. Ascospores colourless or brown, transversely septate or muriform, I+ blue or I-, 1, 2 or 8 per ascus.

Thelotrema is included in the family Thelotremataceae with the genera Conotrema, Diploschistes, Gloeolecta, Myriotrema, Ocellularia and Ramonia [Henssen and Jahns "Lichenes ...." Georg Thieme, Stuttgart, (1973); Hale, Bull. Br. Mus. nat. Hist. (Bot.) 8 (3): 227-332 (1981)]. It is characterised by the presence of periphysoids. Differences between closely related genera Myriotrema and Ocellularia are discussed by Hale (1981, loc. cit. ). Thelotrema is the third largest genus in family with c. 100 species described, mostly from tropical regions, but several species have a wider distribution [Salisbury Lichenologist 5: 262-274 (1972); Hale Smithson. Contr. Bot. 16: 1-46 (1974); Salisbury Lichenologist 7: 59-61 (1975); Bailey and James Lichenologist 9: 170-175 (1977); James Lichenologist 9: 181-183 (1977); Hale Smithson. Contr. Bot. 38: 1-60 (1978); Mycotaxon 11: 130-138 (1980)]. Ten species are known from New Zealand but the genus is still much in need of collection and study especially in North I. One species occurs on rock, the remainder on bark.