Nothogymnomitrion erosum (Carrington & Pearson) R.M.Schust.
Cesia erosa Carrington & Pearson, Pap. & Proc. Roy. Soc. Tasmania 1887: 8. pl. 6, f. 1–19. 1888.
Gymnomitrium erosa (Carrington & Pearson) Bastow, Pap. & Proc. Roy. Soc. Tasmania 1887: 244. 1888 (“erosa”).
Herzogobryum erosum (Carrington & Pearson) Grolle, Oesterr. Bot. Z. 113: 231. 1966.
Nothogymnomitrion erosum (Carrington & Pearson) R.M.Schust., J. Hattori Bot. Lab. 80: 44. 1996.
Type: Tasmania, Mt. Wellington, 1 Jan. 1886, Bastow 284.
Cesia stygia var. denticulata Berggr., On New Zealand Hepat. 4. f. 4. 1898.
Acolea denticulata (Berggr.) Steph., Sp. Hepat. 2: 4. 1901.
Gymnomitrium denticulatum (Berggr.) Müll.Frib., Rev. Bryol. Lichénol. 20: 176–177. 1951.
Lectotype (fide Grolle, 1966b): New Zealand, South Is., Kelly’s Hill, 1200 m, Feb. 1874, Berggren 2870.
[Plate 16C, D, F; Fig. 175: 3, oil-bodies, p. 787]
Distribution and Ecology : Mainly subantarctic in distribution; New Zealand: Campbell Island (570 m), Auckland Islands (170–560 m), Stewart Island (600–690 m), South Island ([695]1010–2130 m), North Island (1240–1700 m); Australia: Tasmania; South Georgia, Falkland Islands (Engel, 1990a); Tierra del Fuego: Isla de los Estados; Brunswick Peninsula, southern Patagonian Channels; Tristan da Cunha. In New Zealand known from Fiordland, Otago, Westland, Canterbury, Marlborough (Tapuae o Unuku), Sounds–Nelson, Southern North Island (Tararua Ra.), Taranaki, Volcanic Plateau and Gisborne (Mt. Hikurangi) EPs.
This species is a common penalpine–alpine plant and is more frequently in the South Island. In the North Island it is associated with volcanic areas, occurring on Mt. Taranaki (Schuster, 1996d) and the central volcanic region in Tongariro Natl. Park. It occurs on rock walls, cliff faces and ledges of outcrops, mostly where a thin soil layer has accumulated, as well as on boulders, frequently on their exposed faces and often where some soil has accumulated. In the alpine zone also on ice-scoured slopes as well as bare soil of steep slopes below cliffs, sometimes on wet rock faces or in snowmelt streams, e.g., on Mt. Burns (Fiordland) where it occurs with Pachyglossa tenacifolia. In such alpine habitats it occurs with Acrolophozia pectinata, Andreaea acuminata, A. acutifolia, Conostomum pusillum, Dicranum aucklandicum, Gymnomitrion cuspidatum, Herzogobryum teres, Jamesoniella colorata, Lepidozia obtusiloba, Racomitrium striatipilum, Rhacocarpus purpurascens, Solorina crocea and Usnea contexta. On the summit of Mt. Rakeahua (Stewart Island, 600–690 m), occurring on the sheltered top of a rock face of a large rock outcrop in mosaic communities of penalpine cushion vegetation, herbfields, Chionochloa, prostrate Leptospermum scoparium, Olearia colensoi 0.5–2 m tall and significant areas of exposed rock. This species is able to tolerate xeric conditions perhaps better than any other alpine hepatic. On exposed boulders, for example, it forms a crust with a few species of mosses. It also commonly occurs on steep slopes over exposed soil and stones, there also forming an inconspicuous crust.
Rarely associated with forests, e.g., found on the face of a huge boulder near Lake Marion (Fiordland Natl. Park, 695 m) at the edge of a rather open forest dominated by Nothofagus menziesii.
For description see the genus.
Comments : This species may be readily identified by the marginal row of leaf cells, which is hyaline, exceedingly thick-walled, with their free walls projecting as irregular, extremely thick-walled, solid, notably irregular “knobs.” The thickened tips at times equal or exceed the length of the cell lumen. It is more common than Herzogobryum teres and is usually distinguishable from that species by the leaves being more imbricate and by a dirty golden brown color rather than a crimson tinting characteristic of H. teres.
