Hymenophore annual, loosely attached, readily lifting, arachnoid-mucedinoid, forming small, irregular areas to 4 cm. long; surface white, drying white, slightly tufted; margin thinning out, white, loosely attached, arachnoid. Context composed of a few repent hyphae to 7 µ diameter, wall 0.25 µ thick, branched, septate, with large clamp connections, fertile hyphae vertically arranged, sparsely branched, bearing branchlets in cymes upon ends of which are carried basidia and paraphyses. Basidia ventricose-eylindrical, 16-24 x 5-7 µ, bearing 4-6, sometimes 8 spores on sterigmata to 10 µ long. Spores pyriform or obovate, apiculate, 5-7 x 3.5-4.5 µ, smooth, hyaline.

DISTRIBUTION. New Zealand.

HABITAT. Effused on decorticated decaying wood.

Hymenophoruin arachnoideum-mucidum, aequum, effusum, superficie alba, leviter cristata. Hyphae nodulosae, ad 7 µ diam., pariete 0.25 µ crasso, levi. Basidia ventricosa cylindricalia, 16-24 x 5-7 µ, 4-6 sporas in sterigmatis ad 10 µ longis gerentia. Cystidia absentia. Sporae pyriformes, apiculatae, 5-7 x 3.5-4.5 µ, leves, hyalinae.

From others with clamp connections the species is separated readily by the large ventricose-cylindrical basidia and small pyriform spores. The hymenophore is delicate, snow white, loosely attached, and hyphae possess such delicate walls that they collapse readily. As they do not stain with aniline blue, their structure is difficult to interpret. Large and conspicuous clamp connections are present at all septa, and the repent hyphae branch at a wide angle.

Unknown host. Otago. Morrison's Creek, Dunedin, 500ft., June, 1952, G.T.S. Baylis, type collection, P.D.D. herbarium No. 11581.

The spores of S. otagense are slightly smaller than Cunningham's measurements (5-7 x 3.54.5 µm). This brings it in the range of S. diademiferum (Bourdot & Galzin) Donk, a widely distributed species growing on a large variety of woody substrates. Eriksson et al. (1984) described the spores of S. diademiferum as ovoid to subglobose, (3.5-)4-5.5(-6) x (2.5-)3-3.5 µm; the spores from a French collection of S. diademiferum (LY 3.454) measured 4-5 x 2.5-3.5 µm. Sistotrema otagense differs from S. diademiferum only in the broader basal hyphae and the slightly different shape of the spores.

Holotype: on unknown host, New Zealand, Otago, Dunedin, Morrison's Creek, coll. G.T.S. Baylis, Jun. 1952 (PDD 11581).