MATERIAL STUDIED: New Zealand, South Island, North Canterbury, Arthur's Pass National Park, Old Coach Rd, on fallen branch of Nothofagus solandri var. cliffortioides, M. Rajchenberg 10060, 10066, 5.V.89; Mid Canterbury, Craigieburn Forest Park, on N. solandri var. cliffortioides, M. Rajchenberg 10070, 5.V.89; Otago Lakes, Mt Aspiring National Park, track to Blue Pools, on fallen branch in N. menziesii forest, M. Rajchenberg 10098, 8.V.89; Hokonui State Forest, vic. Dunsdale Amenity area, on fallen branch, P.K. Buchanan 85/172, 22.IV.89 (sub. Tyromyces sp., PDD 53806). Argentina, Rio Negro, Nahuel Huapi National Park, Puerto Blest, ad truncum Nothofagus dombeyi, H. Spinedi & C. Amos 197, 9.IV.1980, BAFC 27610 (holotype).

Fruit body annual, effused-reflexed, first forming small circular patches that coalesce, each patch giving rise to 1-several reflexed portions or pilei that may fuse laterally, remain separated, or become imbricate. Effused portion of variable size, up to 7 x 6 x 0.4 cm. Reflexed portion flabelliform or spathulate, first totally white, glabrous or velutinate, developing more or less abundant strands of dark vinaceous or blackish hairs (Fig. 3). These strands have a radial disposition, first being aerial and erect, later totally procumbent on the pileus. The number of strands may increase gradually or dramatically towards the margin. When mature these strands totally cover the pileus, resembling veins, with some strands overlapping some of the others and making the pileus surface black and glabrous. Hymenial surface white and remaining so upon drying. Pores angular, 4-6 per mm, with entire but irregular and dentate dissepiments. Margin sterile, incurved. Context white, up to 1.5 mm thick. Tubes white, up to 2.5 mm long, friable upon drying. Hyphal system monomitic. Generative hyphae clamped, 3-7 µm diam., hyaline, thin-walled in the growing margins but soon regularly or irregularly thick-walled, swelling in 5% KOH, acyanophilous, IKI-, giving a positive metachromatic reaction in cresyl-blue. Dark hairs or veins on the pileal surface formed by dark fuscous hyphae. Tube trama hyphae are up to 5 µm diam. Basidia cylindric or slightly claviform, with a slight constriction, 12-17 x 3-4 µm. Spores cylindric, some slightly curved, 4-5 x 0.8-1 µm, with thin, hyaline walls, IKI-, acyanophilous. Cystidia absent (Fig. 4).
Associated wood-rot is chestnut coloured. CULTURAL STUDIES: Performed with BAFC/cc 575, from specimen M. Rajchenberg 10066 (above).
MACROSCOPIC CHARACTERS (Fig. 5): Growth very slow, up to 4 cm rad. in 6 weeks. Mat creamy white but poorly developed. Margin regular, appressed, and subfelty. Mat subfelty, farinose throughout, with slightly marked radial stripes, tightly felty around the inoculum. Odour: none.
OXIDASE REACTIONS: tannic acid: -, 0 mm; gallic acid: -, trace; tyrosinase: +, 0 mm
MICROSCOPIC CHARACTERS (Fig. 6): Advancing generative hyphae clamped, 4-5 µm diam., thin-walled, infrequently branched. Older generative hyphae much branched, 1.5-5 µm diam., with short, digitiform branches that become sclerified; and with irregular wall thickenings in the wider hyphae. These types of hyphae increase in number towards the inoculum.
CODE: 1.3c.9.32.36.38.47.54.

REMARKS: Postia venata was first described from a single collection from southern Argentina, growing on a fallen trunk of Nothofagus dombeyi (Rajchenberg 1983). Since then it has been found frequently in the Nothofagus forests of Argentina (Rajchenberg 1993). The present records from New Zealand expand its distribution (Rajchenberg 1989). Macroscopically, P. venata may be confused with Tyromyces atrostrigosus (Cooke) G.H. Cunningham (1965), which also possesses more or less conspicuous tufts of hyphae. Nevertheless, the latter species differs macroscopically by its strictly flabelliform fruit bodies and by its context and tubes becoming blue upon drying and handling. Microscopically T. atrostrigosus differs in its allantoid basidiospores that are wider than 1 µm (Fig. 4E), and by becoming blue in Melzer's reagent. This species belongs in Postia Fr. because of its monomitic hyphal system, hyaline spores, clamped generative hyphae that become metachromatic in cresyl-blue, and the association with a brown wood-rot (David 1980; Rilich 1982).
The following new combination is proposed:
Postia atrostrigosa (Cke) comb. nov. Basionym: Polyporus atrostrigosus Cke, Grevillea 19: 2. 1890.
Postia atrostrigosa is part of a complex of species surrounding Postia caesia (Schrad.: Fr.) Karst., given the blue colouration of the fruit bodies upon bruising or drying and the amyloid, allantoid basidiospores.
Postia venata may also be confused with Tyromyces setiger (Cooke) G.H. Cunn. (Cunningham 1965; Hood 1992), which possesses allantoid spores and a strigose pileus. Nevertheless, T. setiger differs in the following characters: fruit bodies strictly pileate, not effused-reflexed; pilear surface white and uniformly strigose, with hyaline tufts of hyphae; context up to 30 mm thick and tubes up to 10 mm long; spores allantoid, 4-5 x 1-1.5 µm (Fig. 4D). I have confirmed these observations in two collections of T. setiger: New Zealand, Hawke's Bay, Dannevirke, W. Colenso b517, PDD 39360 (part of type); Auckland, Campbells Bay, on Pittosporum tenuifolium, J. Dingley, Jul. 1953, PDD 13427. Cunningham (1965) stated that T. setiger is associated with a white wood-rot. This needs confirmation, as its morphological features support the inclusion of this species in Postia, a brown wood-rotting genus.