Megalocystidium brunneum S.H. He, 2025

Xu, Y. L., Cao, Y. F., Liu, S. L., Nakasone, K. K. & He, S. H., 2025, Taxonomy and phylogeny of Stereaceae (Russulales, Basidiomycota): two new genera, nine new species and twenty new combinations, Persoonia 54 (1), pp. 119-145 : 139-140

Megalocystidium brunneum S.H. He , sp. nov. MB 843405 . Figs 10E , 11 .

Etymology: The species epithet “ brunneum ” refers to the brown basidiomes.

Typus: China, Yunnan Province, Baoshan County, Gaoligongshan Nature Reserve , on fallen angiosperm branch, 30 Nov. 2015, S.H. He, He 3447 ( holotype BJFC 021843 , isotypes in BJM, CFMR) .

Basidiomes annual, resupinate, effused, adnate, easily separated from the substrate, coriaceous, brittle when dry, first as small round patches, later confluent. Hymenophore smooth, greyish brown [6B(3–6)], brownish orange [6C(3– 8)] to light brown [6D(3–8)], turning reddish-black in KOH, uncracked; margin abrupt, slightly elevated, indistinct and concolourous with hymenophore. Context light brown, up to 1.5 mm thick. Hyphal system monomitic; all hyphae without clamps. Subiculum well-developed; hyphae colourless to pale yellow, thick-walled, smooth, rarely branched, moderately septate, tightly interwoven, more or less parallel to substrate, 2–3 µm diam. Subhymenium indistinct; hyphae colourless, thin- to thick-walled, smooth, tightly interwoven, 2–2.5 µm diam. Gloeocystidia vesicular to racket-shaped, colourless, slightly thick-walled, smooth, embedded, 25–40 × 15–25 µm. Acanthohyphidia numerous, variable in shape and size, mostly subclavate to subcylindrical, with few to many spines at apex, colourless, thin- to slightly thick-walled, 20–40 × 2–6 µm. Hyphidia present, colourless, thin-walled, smooth, slightly branched. Basidia not seen; basidioles numerous, clavate, colourless, thin-walled, smooth, with a basal septum. Basidiospores subcylindrical to subfusiform, colourless, thin-walled, smooth, amyloid, acyanophilous, (9–) 10–12 (–12.7) × 4–5 µm, L = 11.3 µm, W = 4.7 µm, Q = 2.4 (n = 12/1).

Additional specimens examined: China, Yunnan Province, Baoshan County, Gaoligongshan Nature Reserve , on fallen angiosperm branch, 30 Nov. 2015, S.H. He, He 3407 ( BJFC 021803 , CFMR) ; Yongde County, Daxueshan Nature Reserve , on fallen angiosperm branch, 28 Aug. 2015, S.H. He, He 2735 ( BJFC 021173 ) .

Notes: Megalocystidium brunneum is characterized by brown basidiomes, vesicular to racket-shaped gloeocystidia, numerous acanthohyphidia and large cylindrical basidiospores. Megalocystidium chinense is similar to M. brunneum by sharing basidioma colour and large cylindrical basidiospores but differs in having brown gloeocystidia and hyphidia ( Boidin et al. 1979). Megalocystidium wakullum differs from M. brunneum by having subcylindrical gloeocystidia and smaller basidiospores (8–10 × 3–3.5 µm; Burdsall et al. 1981).

Figures

Fig. 10. Basidiomes of Megalocystidium spp. A. M. chinense He 5119 (BJFC 024637). B. Eichleriella chinensis Licent 718 (PRM 501018, syntype). C. Stereum peculiare TAA 10185 (LY 8630, isotype). D. Stereum peculiare TAA 101891 (BPI 0349308, paratype). E. M. brunneum He 3447 (BJFC 021843, holotype). F. M. effusum He 2526 (BJFC 020979, holotype). Scale bars = 1 cm.

Fig. 11. Microscopic structures of Megalocystidium brunneum He 3447 (BJFC 021843, holotype). A. Basidiospores. B–D. Acanthohyphidia. E. Gloeocystidia. F. Hyphidia. G. Generative hyphae from subiculum. Scale bars = 10 µm.