Bambusa sp. Auckland: Mt. Eden, 350ft., March, 1950, G.H.C., type collection, P.D.D. herbarium, No. 10596. Rhipogonum scandens Forst. Auckland: Hick's Bay, 300ft., May, 1952, G.H.C.

Hymenophore annual, slightly adnate, membranous, effused. forming linear areas to 20 x 3 cm.; surface white, becoming pallid cream, even, not creviced; margin thinning out, white, arachnoid, adnate. Context white, 15-25 µ thick, composed of a basal layer of compact parallel hyphae and an intermediate layer of erect, densely compacted hyphae which collapse and become pseudoparenchymatous; generative hyphae 3-3.5 µ diameter, wall 0.2 µ thick, naked, hyaline, branched, septate, with clamp connections. Hymenial layer to 30 µ deep, of basidia and paraphyses. Basidia clavate, slightly projecting, 24-36 x 7-8 µ, 4-spored; sterigmata somewhat stout, to 6 µ long. Paraphyses subclavate, cylindrical, or as frequently obclavate, about half the size of the basidia. Spores usually depressed-globose or subglobose, 8-10 x 7-9 µ, umbonate, wall minutely closely verruculose, hyaline, 0.5 µ thick.

DISTRIBUTION. New Zealand.

HABITAT. Effused on bark of dead stems.

Hymenophorum membranaceum, leviter adnatum, effusum; superficie alba deinde pallide cremea, non rimosa. Hyphae contextus fibulatae, 3-3.5 µ diam., nudae. Basidia 24-36 x 7-8 µ, 4 sporis. Sporae depresso-globosae, umbonatae, 8-10 x 7^-9 µ, subtiliter dense verruculosae, hyalinae.

Identified readily by the unusual spores, somewhat large basidia, tenuous context and white, non-creviced, membranous hymenophore. Spores are commonly depressed-globose and attached to the sterigmata by a definite umbo on the middle of one flattened side. At first they lie with long axes nearly parallel with that of the basidium; as they mature spores become oriented with the umbo downwards, and when detached bear this structure permanently. The hymenial layer soon collapses so that developing basidia may be seen only in sections taken from the growing periphery. The base of the plant tends to lift from the substratum when the ventral surface is seen to be polished and discoloured.

TYPE LOCALITY: Auckland: Mt. Eden, 350ft., March, 1950, G.H.C., type collection, P.D.D. herbarium, No. 10596.

Corticium umbonatum is a typical species of Xerrasma by its lateral basidia and rugose spores and is known from different kinds of bamboo; Arundinaria, Pseudosasa and once on Ripogonum (Liliaceae). Cunninghammyces Stalpers is considered as a synonym of Xerrasma Donk.

Basidiome effused, pellicular to thin membranaceous. Hymenial layer easily separable from poorly developed subiculum and substrate. Hymenial surface even, whitish to cream-coloured when old. Margin indistinct; hyphal strands absent. Subicular hyphae somewhat thick-walled, 2.5-6.5 µm wide. Subhymenial hyphae hyaline, thin- to slightly thick-walled, 2.5-4 µm wide. Clamps present at all primary septa. Cystidia and hyphidia absent. Basidia hyaline, thin-walled, clavate to urniform, often with a basal swelling (probasidium), terminal or lateral (pleurobasidia), 22-45 X 6-7.5 µm, with 4 sterigmata up to 7 µm long. Spores hyaline, thin- to slightly thick-walled, globose, 7.5-9.5 µm diam., echinulate with smooth suprahilar plage, not amyoid; most spores with a large globule, which may cause a thick-walled appearance.