There is a good description in Cunningham (1965: 229). The hyaline, cylindrical spores from the type specimen measure 7-8.5 x 2-2.5 µm, somewhat larger than the dimensions given by Cunningham (1965). As noted by Cunningham, Phellinus ferreus (Pers.) Bourd. & Galz. is closely related but differs in being always adnate, never effused-reflexed nor with a black pileus surface as in pileate forms of P. tawhai.

Holotype: PDD 5509 - New Zealand, Taupo, Mt Tongariro, headwaters of Pangarara River, Dec. 1946, G.H. Cunningham, on Nothofagus solandri (Hook. f.) Oerst. var. cliffortioides (Hook.f.) Poole.

Coprosma robusta Raoul Auckland. Paparata, 300 feet, Oct. 1946, G.H.C. Nothofagus cliffortioides (Hook.f.) Oerst. Auckland. Headwaters of Pangarara River, east slope of Mt. Tongariro, 4,000 feet, Dec. 1946, G.H.C., type collection; Bank of Oturere River, east slope of Mt. Tongariro, 3,000 feet, Dec. 1946, G.H.C.; Beech forest, Kaimanawa Range, 3,000 feet, Dec. 1946, G.H.C.

Hymenophore obscurely stratose, linear when to one metre long, 5 cm. wide, 1-7 mm. thick, or. irregularly orbicular when to 5 cm. diameter, with outlying orbicular islands; margin lifting slightly, irregularly lobed, 1-2 mm. wide, finely pubescent, ferruginous, greyish when old; surface uneven, nodose, often undulate, when fresh smoky grey or greyish brown, becoming dull ferruginous to umber, and much creviced when old. Pores in two or three obscure layers, each 1-2 mm. deep, ferruginous in section, round, 75-150 µ diameter, most about 100 µ, or 5-7 per mm.; dissepiments equal, 50-400 µ thick, most 100-200 µ, apex equal, finely velutinate with protruding hyphae usually coated with fine crystals. Context to 2 mm. thick, chestnut or ferruginous brown, densely woven, with abundant crystals; skeletal hyphae 3-3.5 µ thick, lumen 1 µ, yellow-brown, aseptate, sparsely branched, somewhat undulate; generative hyphae 2-3 µ thick, thin-walled, tinted yellow or hyaline, branched, septate. Setae mostly subulate, a few ventricose, chestnut brown, 30-40 x 6-8 µ, most 30-32 µ long. Basidial type honeycomb, basidia clavate, 8-12 x 4-5 µ. Spores cylindrical with rounded ends, 5-6 x 1.5-2 µ, smooth, hyaline.

DISTRIBUTION: New Zealand.

HABITAT: On bark of fallen branches, dead branches attached to living trees, or upright dead saplings, associated with an active white rot.

Hymenophorum obscure stratosum, lineare, ad 1 m. longum, 5 cm. latum, 1-7 mm. crassum; margo irregulariter lobatus, 1-2 mm. latus, subtiliter pubescens, ferruginous; superficies iniqua, nodosa, saepe undulata, primo nebulosa, demum sordide ferruginea vel umbra-brunnea rimosaque. Pori 1-2 mm. profundi uterque lamella, rotundi, 75-100 µ diametro; dissepimenta aequales, 50-400 µ crassa, subtiliter velutinata. Hyphae skeletales 3-3.5 µ crassae, lumine 1 µ, luteo-brunneo, aseptato, sparse brachiato; hyphae generatoriae 2.5-3 µ crassae, parietibus tenuibus, flavo tinctae vel hyalinae, brachiatae, septatae; setae subulatae, 30-40 x 6-8 µ. Sporae cylindraceae, 5-6 x 1.5-2 µ, leves, hyalinae.

In microscopic features the species agrees closely with F. ferrea, possessing similar spores, setae, skeletal and generative hyphae. It differs in the surface, colour and marginal characters of the hymenophore, and especially in the smaller pores with thicker dissepiments. Pores are 75-150 µ diameter and dissepiments 50-400 µ thick, whereas those of F. ferrea are 100-200 µ diameter, and 50-100 µ thick respectively. The plant is common on Nothofagus cliffortioides in the National Park region, where it is associated with an active white rot of dead saplings and branches of this host. Its specific name has been taken from the generic name tawhai given by the Maori to most species of beech.

Auckland. Headwaters of Pangarara River, east slope of Mt. Tongariro, 4,000 feet, Dec. 1946, G.H.C., type collection