Cunningham (1965: 90) provided a good description of the species and transferred it to Grifola S.F. Gray because fruit-bodies usually consist of a cluster of imbricate pilei joined by a tuberous base. G. frondosa (Fr.) S.F. Gray, the type species, is similar to G. rosularis in having the same type of hyphal system and spores, although both spores and pores of G. frondosa are larger.
G. rosularis could be considered to belong in Tyromyces, which includes many species with imbricate basidiocarps, a monomitic hyphal system, and subglobose to ellipsoid, nonamyloid, nondextrinoid spores; T. pubescens (Fr.) Pilat is a representative example of this group. However, almost all Tyromyces species produce applanate basidiocarps on dead wood rather than semistipitate basidiocarps arising from a common base. Thus we maintain the species in Grifola.

Holotype: PDD 3914 - New Zealand, Gisborne, Lake Waikaremoana, Waikareiti Track, Jan. 1933, J.G. Gibbs, on Nothofagus sp.

Accepted as Tyromyces falcatus.
The description by Cunningham of macroscopic characters is satisfactory, but there are misleading statements about the microscopic characters. The septa of the generative hyphae are not simple, but have large, conspicuous clamps. The basidiocarp is composed of mostly unbranched hyphae with very thick walls. These vegetative hyphae were described by Cunningham as binding hyphae but appear in the illustration (Cunningham, 1965: fig. 28) as skeletal hyphae. We interpret them as skeletal hyphae with scattered side-branches, the side-branches not being as common or regular as described by Cunningham. The thick hyphal walls often appear to be multilayered and are refractive in KOH. T. falcatus has a harder texture than most other species in Tyromyces.

Holotype: PDD 15612 - New Zealand, Westland, Ahaura, Orwell Creek, Apr. 1955, J.M. Dingley, on Nothofagus fusca (Hook. f.) Oerst.

Hymenophore annual, hard and horny though brittle, compound, rosulate, of numerous (5-15) pilei united by a broad stem-like base to a common stroma. Pilei simple or branched, digitate, spathulate, or urceolate, to 3 cm. x 3 cm. x 1-5 mm., attached by a broad base about the width of the pileus; surface cream, becoming pallid ochre, irregular, radiately sulcate, finely tomentose, cuticle to 100 µ thick, composed of densely woven hyphae arranged in a palisade embedded in mucilage; margin reddish-brown, or concolorous, thin and horny, translucent, much lobed or crenate, acute or bluntly rounded; hymenial surface decurrent, cream or pallid ochre, darker peripherally, with or without a narrow sterile margin, dissepiments not toothed. Context straw colour, 1-2 mm. thick, of radiately arranged hyphae, firm but brittle; generative hyphae 6-8 µ thick, wall l µ, ribbon-like, lumen staining, sparsely branched, septate, with large clamp connections. Pores straw colour in section, 1-1.5 mm. deep, 150-200 µ diameter, or 4-5 per mm.; dissepiments 50-200 µ thick, equal, of woven mainly parallel hyphae, apex equal, finely velutinate. Basidial type clavate, basidia clavate, 14-16 x 5-7 µ, persistent. Spores broadly obovate, 4-5 x 3.5-4 µ, smooth, hyaline.

New Zealand.

Separated from P. anthracophilus and P. rosulatus by the palisade cuticle of the pileus, smaller pores and differently shaped spores. The hymenophore is hard and horny, almost cartilaginous, and pilei are firmly cemented together.

Type: Lignicolous Fungi; Description: Basidiomata annual, sometimes solitary but more usually compound, composed of many (up to 28) overlapping pilei, often forming a rosette, fleshy cartilaginous, brittle and easily snapped when young, attached by a common, broad lateral base. Pilei fan-shaped or spatulate, 15–25 mm wide, 1–5 mm thick, often merging laterally. Pileus surface delicately tomentose, white to cream, margin reddish brown, lobed. Pore surface plane, with a sterile border up to 2 mm wide, cream to light brown; pores large, 2–4 per mm. Context cream to light brown, up to 2 mm thick. Hyphal system dimitic. Basidiospores obovate, 5–8 × 4–5 μm, smooth, hyaline.

Distribution: Bay of Plenty, Taupo, Gisborne, Nelson, Buller, Westland, Fiordland, North Canterbury, Otago Lakes.; 1st Record: Colenso (1887: as Favolus hispidus var.).

Significance: Recorded as the cause of butt rot in a living Nothofagus menziesii tree (Hood 1992).; Host(s): Nothofagus menziesii.