NEW ZEALAND: North Island, Northland, Hokianga Co., Waipoua Kauri Reserve, 12.V.83, R. H. Petersen no.55634 [Holotype, TENN no. 44402].

Basidiomata marcescent. Pileus 0.5-l mm diam, convex, expanding to plano-convex; surface even (non-striate), minutely granulose, white. Lamellae absent; hymenophore smooth, white. Stipe 0.5-1 x 0.1 mm, central or slightly eccentric, often curved, terete, equal, pruinose, insititious, white overall. Odour and taste not recorded. Basidiospores 12.8-17.2 x 3.8-4.8 µm [x = 14.7 x 4.2 µm, s = 1.3 x 0.3, E = 2.7-4.4, Q=3.5, sQ = 0.4, n = 20], subfusiform, inequilateral in profile, hyaline, inamyloid, smooth. Basidia 24-32 x 6.5-8.0 µm, tetrasporic, cylindric or subclavate, hyaline, contents tawny in Melzer's reagent. Basidioles clavate or ventricose. Hymenial cystidia ~32 x 10 µm, lageniform or ampullaceous, non-refractive, hyaline, thin-walled or firm-walled (walls up to 0.5 µm thick). Pileipellis hymeniform; elements up to 28 µm diam, smooth (non-diverticulate), broadly clavate or vesiculose and short pedicellate, hyaline, inamyloid; walls up to 1 µm thick; ventricose dermatocystidioid elements scattered, scarcely projecting. Tramal hyphae 3-8(-13) µm diam, interwoven, hyaline, inamyloid, non-gelatinous, clamped; walls <l µm thick. Stipe tissue monomitic. Stipe cortical hyphae 3-10 µm diam, parallel, hyaline, inamyloid, smooth, clamped; walls up to 2 µm thick. Stipe medullary hyphae similar but thin-walled. Caulocystidia scattered, 4-16 x 6-9 µm, cylindric or clavate, thick-walled, hyaline, inamyloid. Scattered on senescent monocotyledonous leaves (probably Astelia).

Pileus 0.5-1 mm latus, convexus vel plano-convexus, albus. Lamellae nullae. Stipes 0.5-1 x 0.1 mm, centralis vel eccentricus, falcatus, pruinosus, insititius, albus. Basidiosporae 12.8-17.2 x 3.8-4.8 µm, subfusiformes, laeves, hyalinae, inamyloideae. Basidia tetraspora, Hymenii cystidia lageniformia. Pileipellis hymeniformis ex elementis clavatis vel vesiculosis, hyalinis; dermatocystidia rara. Trama ex hyphis inamyloideis, fibulatis. Caulocystidia clavata vel cylindrica, crassitunicata. In foliis monocotyledonum.

Marasmius pusillissimus is characterised by minute, entirely white basidiomata that lack lamellae, pruinose, insititious stipe, and growth on monocotyledonous leaves. In addition, inamyloid, clamped tramal hyphae and long spores are distinctive. Although basidiomata size, stature and reduced hymenophore suggest that this taxon should be looked for in the cyphelloid series of the Tricholomataceae, several features indicate that the species is best placed in Marasmius sect. Epiphylli Kuhner subsect. Epiphyllini Singer. Characters which support this disposition include: a) hymeniform pileipellis of smooth, non-diverticulate elements plus scattered dermatocystidioid cells; b) inamyloid tramal hyphae with clamp connections; c) ventricose-ampullaceous hymenial cystidia; d) absence of pigments; and e) insititious stipe. Taxa in sect. Epiphylli show hymenophore development ranging from well-developed lamellae to radiating folds or ridges, but few taxa form hymenia entirely devoid of macroscopic differentiation. One such species superficially similar to M. pusillissimus is M. martinii Singer [ut M. martini (Singer, 1958) nom. nov. for Cymatella longipes Martin (1944)]. Both M. pusillissimus and M. martinii form very small, pigmentless pilei with entirely smooth hymenia. Marasmius martinii differs in forming a longer (up to 16 mm) and darkly pigmented stipe (yellow-brown or nearly black), shorter spores (9-11 µm), and in growing from bark of fallen branches [fide Martin 1944; Singer 1965, 1976]. Marasmius martinii is known only from Colombia, South America.
A second species superficially similar to M. pusillissimus was described from Sierra Leone as Marasmius cymatelloides Dennis & Reid (1957). Subsequently, Singer (1961) established the monotypic genus Palaeocephala Singer based on the type specimen of M. cymatelloides. Palaeocephala is closely allied with Gloiocephala Massee, a genus considered by some as congeneric with Marasmius (see Bas 1961; Noordeloos 1981). Palaeocephala cymatelloides differs from M. pusillissimus in having dextrinoid tramal hyphae, abundant basal mycelium (i.e., stipe non-insititious), absence of hymenial cystidia, and in growing on leaves of Baphia pyrifolia Baill. [Leguminosae] (fide Dennis & Reid 1957).

Holotypus: TENN no. 44402.

New Zealand, North Island: North Auckland, Hokianga Co., Waipoua Kauri Reserve, 12.v.1983, R. H. Petersen 55634 (TENN 44402, holotype). Gisborne, Urewera N. P., near Headquarters, 31.v. 1981, Horak (PDD; ZT 849).

Description of Second New Zealand Record
Pileus to 3 mm, convex to flat-expanded, old specimens also with depressed centre, subumbilicate, whitish, minutely pruinose, margin subciliate. Lamellae none, hymenophore smooth or occasionally with a few low radially arranged folds, whitish. Stipe to 4 X to 0.2 mm, central (rarely eccentric), cylindrical, straight or curved, whitish to hyaline, minutely pruinose overall, dry, solid, solitary in groups, insititious (byssus or basal disc absent). Odour absent. Basidiospores 12-16 X 4.5-5.5 µm, subfusiform (reminiscent of boletoid spores), inequilateral in profile, often with significant supra-apicular depression, smooth, hyaline, inamyloid. Basidia 23-30 X 8-11 µm, tetrasporic, subclavate, clamped. Hymenial cystidia inconspicuous, lageniform. Pileipellis hymeniform, composed of subcylindric, clavate or broadly fusiform ceils, 30-60 X 8-20 µm, non-gelatinous walls up to 1µm diam., hyaline, smooth. Pilocystidia scattered, up to 90 X up to l6 µm, fusiform with tapering, rounded neck, thin-walled, hyaline. Margin of cap with scattered, bristle-like, cylindrical 'hairs', 3-7 µm diam., subgelatinous, conpicuously thick-walled (up to 3 µm diam.), with distinctive lumen at apex, often encrusted with colourless matter. Oleiferous hyphae absent. Stipe tissue monomitic. Stipe conical hyphae 3-8 µm diam., parallel, cylindric, hyaline, smooth. Caulocystidia numerous, 15-50 X 8-18 µm, polymorphic, ranging in shape from cylindric to broadly fusoid, walls up to 1.5 µm thick, hyaline, clamped.

On rotting leaves of Astelia sp. (Asteliaceae), already infecting healthy leaves and consistently associated with leaf spots. Known from North Island of New Zealand.

This represents a second New Zealand record for this tiny species reported first from Waipoua Kauri Reserve, Hokianga Co. (Desjardin and Petersen 1989).
The material described above differs slightly from the holotype in showing larger pilei, longer pilocystidia, and the presence of scattered bristle-like marginal hairs. Gloiocephala Massee, Grevillea 21:33(1892)