Gymnopus pyracanthoides R.H. Petersen, 2016

Petersen, Ronald H. & Hughes, Karen W., 2016, Micromphale sect. Perforantia (Agaricales, Basidiomycetes); Expansion and phylogenetic placement, MycoKeys 18, pp. 1-122 : 75-81

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Gymnopus pyracanthoides R.H. Petersen

sp. nov.

8. Gymnopus pyracanthoides R.H. Petersen sp. nov.


Costa Rica, Prov. San José, San Gerardo de Dota, Albergue de Montaña, Savegre, 9°33'2" N, 83°48'27"W, 21.VI.1995, coll RHP, TFB 7879 ( TENN-F-53736).


Latinized; resembling Pyracantha , referring to spike-like setulae on pileipellis broom cell-like hyphal termini.


1) A morpho-species (no DNA sequences available); 2) broom cell-like hyphal termini of pileipellis coarsely thorny; 3) subhymenial hyphae with slime sheath and flake-like encrusting material; 4) rhizomorphs well-developed, curly, sparingly branched; 5) stipe minutely pruinose overall; 6) fruiting on sclerophyllous deciduous leaves.


Basidiomata (Fig. 59A View Figure 59 ) diminutive, arising independent from but gregarious with rhizomorphs. Pileus 3-6 mm broad, strongly convex and in one case slightly umbonate, matt, minutely tuberculate, subtly sulcate or not so; disc "wood brown" 7C4; limb and margin "vinaceous buff" 9B2 to "tilleul buff" 7B2. Lamellae adnexed (Fig. 59A View Figure 59 ), usually weakly pseudocollariate, thickish, subdistant, narrow (<1 mm broad), slightly ventricose, without anastomosis or interveining, without necropigment, total lamellae = 31-33, through lamellae = 10-11, "vinaceous buff" 9B2; lamellar edge entire, not marginate. Stipe 24-38 × 0.3-0.5 mm, appearing glabrous-shining but under magnification (35 ×) very finely pruinose over total length (pruinosity hyaline), stuffed (medulla off-white), insititious, apically concolorous with lamellae, downward quickly "army brown" 8D5, downward "Natal brown" 8E6. Rhizomorphs (Figs 59A View Figure 59 , 60 View Figure 60 ) common, mostly resupinate on leaf surface (both upper and lower side), 0.1 mm broad (extremely slender), only occasionally branched when resupinate; aerial rhizomorphs - 17 × 0.2-0.3 mm, gyrose to curly in aerial portions and frequently branched, glabrous-shining, now strap-shaped where free (aerial portions compressed in drying, not resupinate portions), functionally black in resupinate portions, brass-brown (reminding of M. " flavipes " nom. prov. from Tasmania) to "bone brown" 7F8 in aerial portions. Taste and odor not recorded.

Habitat and phenology.

Known from only the type specimen; fruiting on dead sclerophyllous leaves (probably Quercus ) at high elevation; summer.

Pileipellis (Fig. 61 View Figure 61 ) a dense thatch of diverticulate hyphae and hyphal termini; parent hyphae 2-2.5 µm diam, thin- to firm-walled, hyaline, not involved in slime matrix, producing elongate, jointed, digitate side branches 2-7 × 0.8-1.5 µm, rarely but conspicuously clamped. Pileus and lamellar tramal hyphae 2-5 µm diam, firm- to thick-walled (wall -0.7 µm thick, hyaline), producing thin slime sheaths, ornamented with external “flakes” of encrusting material, infrequently but conspicuously clamped. Pleurocystidia (Fig. 62A-D View Figure 62 ) 21-28 × 5-7 µm, fusiform, with narrowly rounded to acute apex, abundant, thin-walled, conspicuously clamped. Basidioles clavate; basidia (Figs 62E-H View Figure 62 , 63F View Figure 63 ) 19-26 × 6-7 µm, clavate, sometimes very slightly subcapitate, 4-sterigmate, obscurely clamped. Subhymenium often gelatinizing, including bases of basidia and pleurocystidia. Basidiospores (Fig. 59B View Figure 59 ) 6-7.5 × (3-)3.5-4 µm (Q = 1.63-2.33; Qm = 1.94; Lm = 6.85 µm), ellipsoid to elongate pip-shaped, smooth, thin-walled, inamyloid. Lamellar edge fertile; cheilocystidia (Fig. 63A-E View Figure 63 ) scattered, obscure, 22-32 × 5-8 µm, subcapitate to subampulliform, obscurely clamped, hardly projecting beyond basidia, hyaline. Stipe medullary hyphae 3.5-7.5 µm diam, firm-walled, conspicuously clamped, strictly parallel, with minimal slime matrix, hyaline. Stipe cortical hyphae 4-7 µm diam, thick-walled (wall -1.5 µm thick, pigmented), at surface producing side branches as caulocystidia. Caulocystidia (Fig. 64 View Figure 64 ) setoid, -85 × 5-7.5 µm diam, arising as side branches (not clamped), tapering slightly distally, refringent (PhC), in IKI moderately dextrinoid (PhC), yellow-brown (BF).


Presence of slime sheaths surrounding pileus and lamellar tramae as well as the dimensions and shape of cheilocystidia are characteristic of taxa in sect. Perforantia . Conversely, pileipellis presents a very distinctive thatch of broom cell-like hyphal termini rather than repent, encrusted hyphae in a slime matrix as is seen throughout the section. Such a differentiated pileipellis might also qualify for some infrageneric groups of Marasmiellus but would be expected to be without slime deposition. Unfortunately, DNA sequences could not be produced from the only known collection, so molecular placement remains unknown.

Cheilocystidia in G. pyracanthoides resemble those of G. bulliformis (q.v.). They also resemble those described for G. trabzonensis . They may represent some stage of basidial development because basidioles also are clavate, but basidioles are present throughout the lamellae face, while the structures here described as cheilocystidia are found along the lamellar edge. No other differentiated cheilocystidial structures were observed, but some taxa in sect. Perforantia are known to lack differentiated cheilocystidia.

Slime is produced as a thin sheath surrounding individual hyphae, with ornamentation appearing as flakes riding on the exterior of the gelatinized wall. It also appears to obliterate subhymenium. Likewise, stipe medullary hyphae exist in minimal (but present) slime. There is little evidence of a slimy (or gelatinized) matrix in the pileipellis.

Specimen examined.

Costa Rica, Prov. San José, San Gerardo de Dota, Albergue de Montaña, Savegre, 9°33'2"N, 83°48'27, 21.VI.1995, coll RHP, TFB 7879 ( TENN-F-53736; holotype).