Colour of spore print unknown.

Spores 8-11 X 5.5-7 (9.4 X 6.3) µm., Q = 1.49, ellipsoid, hyaline, thin-walled, strongly amyloid. Basidia 15-18 X 6-8.5 µm., short and fat, 2- to 4-spored, sterigmata relatively long (up to 4-5 µm.). Cheilocystidia 35-40 X 3-7 µm., forming a broad band of closely packed, thin-walled, fusiform to narrowly clavate cells, mostly with a smooth apex but sometimes with 1-4 µm. small apical protuberances, yellow-brown plasmatic pigment. Gill edge gelatinised. Pleurocystidia absent. Trama of more or less parallel, narrow (2-3 µm.) hyphae, vinescent-red in Melzer's. Context of thick-walled hyphae of fairly regular cells (15 X 7 µm.), not inflated, vinescent-red in Melzer's. Pileipellis very complex; suprapellis of narrow, gelatinised hyphae, probably separable, with scattered, large bundles of thin-walled hairs; pellis of narrow (5-6 µm.) hyphae with short, sometimes diverticulate protuberances often terminating in inflated cells (10-15 µm. diam.) bearing large numbers of short (1-4 µm.) to long (-10 µm.) protuberances. Beneath the pellis is a subpellis of mostly spherical (4.5-5 µm. diam.) to short cylindrical (9-16 µm. long) elements with very thick (up to 3 µm. wide) walls. Stipe of narrow hyphae, the cortex bearing many long, thick-walled, tapering caulocystidia (85-140 X 6-12 µm. at the base, 2-4 µm. diam. at the tips, some distinctly swollen at the base). In the middle of the stipe are a few conducting hyphae with yellow (KOH), shining contents. Disc consists of thick-walled, hyaline hyphae 4 µm. diam., with a brown, resinous, encrusting pigment; the dark colour at the edge and underside of the disc appears to be due in part to colonies of blue-green algae. No clamp connections seen.

HABITAT: Gregarious, on dead wood in mixed podocarp-dicotyledonous forest.

ETYMOLOGY: The epithet of the new species reflects the almost completely spherical form of the young basidiome.

At first sight, the assigning of this fungus to any section as presently defined raises some problems. The well-developed disc at the base of the stipe and gelatinous pellicle suggest section Basipedes but it would be excluded on account of its green colour (Maas Geesteranus 1980). Maas Geesteranus has not included section Cyanocephalae in his Conspectus, presumably because it comprises only Southern Hemisphere species. This section was introduced by Singer in 1975 but not legitimised until 1986 (Singer 1986), to accommodate three blue to blue-green species; M. cyanocephala Sing., (S. America) M. interrupta (Berk.) Sacc. (Australia), and M. veneta Stev. (New Zealand), all of which Horak (1983) considers to be the same species, namely M. interrupta.

M. globuliformis can be confused with M. interrupta, even when it is found on the same log (PDD 34786), but, when looked at critically, the pileus is seen to be more yellowish-green on a straw-coloured background, rather than blue-green, which would exclude it from section Cyanocephalae. The situation is further confused by the presence of blue-green algae at the edge of the disc, which, when moist, may give a distinctly blue-green colour. The appropriate place for M. globuliformis appears to be section Longisetae, despite the absence of pileal setae and the amyloidity of the spores. There are, indeed, many resemblances to M. longiseta Hohnel, such as structure of the pileipellis, the cheilocystidia and the disc, and the long setiform hairs on the stipe. Although there are no pileal setae, the subpellis in M. globuliformis is composed of conspicuously thick-walled cells very much like the basal cells, which are extended into setae in M. longiseta. Another species of Mycena, M. sublongisetae Z.-s. Bi, has recently been described from China. This differs from M. globuliformis in its larger size, its yellow-brown pileus and orange-yellow lamellae, but it resembles it in having slightly amyloid spores; the pileal setae are intermediate in size between the other two species. The discovery of a third species related to M. longiseta reinforces the segregation of section Longisetae from section Basipedes.