On leaf base of Rhopalostylis sapida, Auckland, Waipoua State Forest, 20.i.l955, J. M. Dingley (HOLOTYPE, PDD 25000).

Fructifications arid-waxy, resupinate, thin, effused, originating as discrete patches, coalescing to form irregular areas to 11 cm in longest dimension, pruinose, creamy-tan to creamy-brown when fresh, changing little on drying: margins concolorous, adnate. In section 80-150 µm thick, consisting of basal layer and hymenium, occasionally two growth layers present. Basal layer to 15 µm thick, composed of indistinct, interwoven, hyaline hyphae lying parallel to substratum, clamp connections present. Hymenium composed of dikaryophyses, gloeocystidia and basidia; dikaryophyses sparse, simple, cylindrical; gloeocystidia abundant, irregularly cylindrical to cylindrical-subclavate, flexuous, arising from basal hyphae or base of fertile hyphae, hyaline at first, contents becoming brownish-yellow, granular, 30-75 x 4.5-8 µm, probasidia broadly obovate, pyriform or subglobose, often short stalked, proliferating through obscure basal clamp connections, formed in terminal groups on erect fertile hyphae, 19.6-25 x 11.2-17.3µm, becoming longitudinally cruciate-septate; sterigmata subulate, to 18 µm long. Basidiospores broadly cylindrical to ovate often flattened on one side, hyaline, apiculate, aguttulate, 17.4-24.8 x 9.3-12.4 µm. Germination by repetition or by stout germ tubes.

Dead angiosperm wood.

Fructificationes aride ceraceae, resupinatae, tenues, pruinosae, cremeo-brunneae; ordo basalis tenuis, factus ex hyphis indistinctis, nodosis. Dikaryophyses rarae, cylindricae; gloeocystidia irregulariter cylindrica ad cylindrica-subclavata, interiora brunneo-lutea, granulosa 30-75 x 4.5-8 µm probasidia late obovata, pyriformia vel subglobosa, 19.6-25 x 11.2-17.3 µm, per longitudinem cruciata-septata: sterigmata subulata, ad 18 µm longa. Basidiosporae late cylindricae ad ovatas, 17.4-24.8 x 9.3-12.4 µm Germinantes per repetitionem, vel per tubulos. Habitat in foliorum basi Rhopalostylidis sapidae.

The presence of gloeocystidia with brownish-yellow granular contents indicate that this species belongs in sect. Bourdotia. In microstructure, Sebacina nikau closely resembles S. pini Jacks. & Martin. It differs in colour of the fructifications, absence of branched dikaryophyses, longer gloeocystidia, and slightly larger aguttulate spores. In addition, S. pini is reported to be restricted to coniferous substrates.
According to Luck-Alien's (1963) classification, S. nikau belongs in Basidiodendron subg. Asarcogloea.

Typus Auckland Province, Waipoua State Forest, 20.1.1955, J. M. Dingley, PDD25000