Material examined- - NEW ZEALAND: South Island, Prov. Nelson, Murchison, Matakitaki, 28 II 969, Horak 69-32 (on Pseudopanax) (SFSU, ZT); Prov. Westland, Ahaura, Kopara, 9 XII 1967, Horak 67-228 (on Pseudopanax) (ZT); Prov. Nelson, Murchison, Matakitaki, 10 II 1969, Horak 69-57 (on Pittosporum) (SFSU, ZT).

Pileus 2-5(-7) mm diam, hemispherical to convex throughout maturation, disc neither depressed nor papillate, margin plicate; surface dull, dry, glabrous; evenly rusty brown to pale soot brown, or with a darker disc, dried orange to pale orangish brown. Texture tough, membranaceous; context very thin. Lamellae subfree to adnexed, subdistant (9-12), lamellulae absent, seldom with 1-series, white to cream; edges even, pale rusty brown to pale brown. - Stipe15-60(-75) x 0.3-0.5 mm, central, cylindrical, equal, wiry, glabrous, shining, insititious, apex cream, black elsewhere; rhizomorphs absent.- Odor and taste not distinctive.
Basidiospores 9-11(-12) x (3.5-)4.0-5.0(-5.5) µm, ellipsoid to subfusoid, sometimes slightly curved in profile, smooth, thin-walled, hyaline, inamyloid.- Basidia 18-30 x 7-9 µm, clavate, 4-spored, clamped. - Cheilocystidiaof 2 types: a) Rotalis-type cells with main body 12-30 x 8-15 µm, broadly clavate, hyaline, thin-walled to slightly thick-walled; divergent setulae 1-2 x 0.5-1.0 µm, cylindrical, thin-walled to thick-walled, hyaline to pale tawny; b) fusoid to ventricose cystidia with elongate neck, 20-36 x 4-10 µm, thin-walled, hyaline.- Pleurocystidia absent.- Pileipellis hymeniform, not mottled, composed of Rotalis-type cells; main body (10-)15-25 x 7-12 µm, clavate to broadly clavate, reddish brown, thick-walled (1-4 µm ); divergent setulae 1-2 x 0.5-1.0 µm , cylindrical; some cells lacking setulae interspersed among Rotalis-type cells; pileocystidia absent.- Pileal and tramal tissue inamyloid, Stipe tissue monomitic; cortical hyphae cylindrical, densely setulose at stipe apex, smooth or with scattered setulae at stipe base, brown, dextrinoid.- Caulocystidia absent.- Clamp connections present.

Habit, habitat and distribution.- Solitary, in groups on rotting leaves of Pseudopanax crassifolium (Scheffleraceae) or Pittosporum eugenioides (Pittosporaceae). Malaya, New Zealand, Sri Lanka.

Marasmius micraster is characterized by convex, plicate, rusty brown to soot brown pilei (yellowish brown to blackish brown in Sri Lankan material), subdistant (9-12), non-collariate lamellae with brownish edges, a long (15-60 mm), glabrous, insititious stipe, basidiospores 9-11 x 4-5 µm, two types of cheilocystidia, and the absence of both pileocystidia and caulocystidia. Marasmius micraster is most closely allied with the southern European M. corbariensis (Roum.) Singer, which differs only in forming strongly intervenose, non-marginate lamellae, a furfuraceous stipe, and scattered pleurocystidia. Marasmius sphaerodermatoides Singer, described from Argentina, is also similar, but differs in forming shorter basidiospores (7-8 µm long), scattered pleurocystidia, and two types of caulocystidia (fide Singer, 1989).
Marasmius micraster was first described from Sri Lanka (Petch, 1948), with pilei reported as 2-3 mm diam and stipes 10-30 mm long. Apparently there is a wide range of basidiome size exhibited by M. micraster. For example, of the two specimens collected on Pseudopanax leaves, Horak # 67-228 forms pilei 23 mm diam and stipes 15-30 mm long, whereas Horak # 69-32 forms pilei 4-7 mm diam and stipes 30-75 mm long. Moreover, the basidiospores of the material collected on Pittosporum leaves (Horak # 69-57) are narrower than those of the material collected on Pseudopanax, measuring 10-12 x 3.5-4.0 µm vs. 9-11 x 4.0-5.0 respectively. Because all other features are indistinguishable, we do not consider these differences taxonomically significant. Corner (1996) recently described M. micraster var. brevipes Corner from Singapore, differing only in forming a short stipe (6-10 mm) and fewer lamellae (4-7).