Gymnopus fragillior 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 : 32-39

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Gymnopus fragillior R.H. Petersen

sp. nov.

3. Gymnopus fragillior R.H. Petersen sp. nov.


United States, Washington, Jefferson Co., Irely Lake Area, North Fork Quinault River, N47°33'47.7", W123°40'12.38", date not recorded, coll M.T. Seidl, ident. S Redhead (as Micromphale perforans ), MTS 3715 ( WTU-F-9293).


fragillior = Latin, more fragile, referring to more diminutive stature than M. perforans .


1) A morpho-taxon (no DNA sequences available); 2) basidiomata slender (stipe 15-25 × 0.4-0.7 mm), diminutive, slender; 3) stipe base (<1 mm) with hirsute, tawny collar; 4) sterigmata stout, subcornute; 5) basidiospores broadly ellipsoid to pip-shaped (Qm =1.68); 6) stipe medullary hyphae thick-walled, not involved in slime matrix.

The following description is based on dried material only.

Basidiomata (Fig. 22A View Figure 22 ) slender, diminutive, attached to individual needles of ? Abies grandis .

Pileus 6-10 mm broad, convex to plano-convex, often somewhat centrally depressed, matt, delicately tuberculate; disc (fresh) pale grey brown, (dry) "army brown" 8D5 to "sayal brown" 6C5; limb and margin (fresh) cream, (dry) "wood brown" 7C4; margin thin; pileus trama dull orange to orange-brown in Melzer’s reagent. Lamellae adnate, distant, thickish, in 2-3 tiers, weakly pseudocollariate, seceding upon drying, (fresh) pallid tan, "tilleul buff" 7B2, "olive buff" 3B3, (dry) slightly necropigmented (near "light ochraceous buff" 5A4). Stipe 15-25 × 0.3-0.5 mm, terete, equal, more or less straight, hollow, non-insititious, lightly vestured to delicately furfuraceous throughout, in contact with lamellae dark brown, apically tan to pale cream ("cinnamon buff" 6B4), downward brown, dark brown, base blackish brown ("clove brown" 6F5, "fuscous black" 6F4); stipe base (<1 mm) a minutely hispid collar, “tawny” 6C6 to "ochraceous tawny;" basal pad restricted, “tawny” 6C6; medulla thin, off-white (not white). Rhizomorphs not observed. Odor alliaceous; taste not recorded.

Habitat and phenology.

Known only from the holotype collection. "Scattered on outer bark of fallen tree, mostly fruiting from needles fallen on log" (teste Seidl) (perhaps Abies grandis ). Seasonality unknown.

Pileipellis a repent, unoriented layer in a thin slime or gelatinous matrix with detersile encrustation material, composed of the following: 1) pileal hairs (Fig. 23B-E View Figure 23 ) 15-75 × 5-10 µm diam, digitate to vermiform, equal, hyaline, firm- to thick-walled (wall -0.5 µm thick), obtusely rounded at apex; 2) repent hyphae 4-13 µm diam, thin- to firm-walled, conspicuously clamped (but with occasional secondary septa), at pileus surface strongly to moderately encrusted (Fig. 23A View Figure 23 ); crust material in scabs, occasionally with suggestion of annular pattern, 0.7-2 µm thick, in subpellis as flakes riding on thin slime sheath. Pileus and lamellar tramae loosely interwoven, dull orange to orange-brown in IKI; hyphae 5-12 µm diam, thin- to firm-walled, with thin slime sheath in KOH, conspicuously clamped. Pleurocystidia (Fig. 24 View Figure 24 ) 28-35 × 5-8 µm, fusiform to narrowly fusiform, conspicuously clamped, hyaline; contents homogeneous. Basidioles (Fig. 25A, B View Figure 25 ) clavate, clamped; basidia (Fig. 25C, D View Figure 25 ) 28-36 × 7-10 µm, clavate, usually subcapitulate, conspicuously clamped, 4-sterigmate; sterigmata -6 × 2.5 µm, stout, subcornute. Basidiospores (Fig. 22B View Figure 22 ) (6-)6.5-7.5(-8) × 3.5-4.5 µm (Q = 1.44-2.00; Qm = 1.68; Lm = 6.90 µm), plump ellipsoid to pip-shaped, smooth, thin-walled, inamyloid. Cheilocystidia not observed. Stipe medullary hyphae strictly parallel, 4.5-14 µm diam, apparently free (not involved in slime or gelatinous matrix), thick-walled (wall-0.7 µm diam, hyaline), obscurely clamped; occasional slender hyphae (4-5.5 µm diam) meandering among broader hyphae. Stipe cortical hyphae 4.5-7.5 µm diam, thick-walled (wall -2.5 µm thick, pigmented, producing caulocystidia as side branches), obscurely clamped. Mid-stipe caulocystidia (Fig. 26 View Figure 26 ) in scattered clusters, setoid, arising as side branches of surface cortical hyphae or as termini, 15-75 × 7-13 µm diam, not clamped, digitate to subvermiform, thick-walled (wall -5 µm thick, pigmented pale yellowish, refringent; PhC). Caulocystidia from stipe base (Fig. 27 View Figure 27 ) densely gregarious, setoid, 20-95 × 7-13 µm, usually straight, tapering somewhat distally, with basal appendage, thick-walled (wall often occluding cell lumen, yellowish, refringent).


A pileipellis involved in slime matrix, lacking diverticulate hyphae and/or broom cell-like termini, coupled with vestured stipe, indicate placement in Gymnopus (Micromphale) sect. Perforantia . There it is distinguished from G. perforans , G. pallidocephalus and other taxa with similar characters. Unusual, however, are the scattered clusters of caulocystidia, the stipe base with delicately hispid, brown caulocystidia and pip-shaped spores. From Mycetinis salalis comb. prov, also in the moist forests of the Pacific Northwest, G. fragillior is immediately separated by spore dimensions (15-17 × 3.5-4 µm; Qm = 4.38 in the former), habitat on conifer needles (rotting wood in the former), different pileipellis structures and absence of cheilocystidia (marasmioid in M. salalis ). From both G. perforans and G. pallidocephalus , which share habitat on conifer needles, G. fragillior is distinguished by non-black stipe (black, vestured and more robust in G. perforans , black and glabrous-shining in M. pallidocephalus ), and common clamp connections (absent in G. pallidocephalus ). Basidiomata of G. bulliformis are somewhat more robust, with pileus somewhat paler and prominent, utriform cheilocystidia (absent in G. fragillior ).

Specimen examined.

United States, Washington, Jefferson Co., Irely Lake Area, North Fork Quinault River, N47°33'47.7", W123°40'12.38", date not recorded, coll M.T. Seidl, ident. S Redhead (as Micromphale perforans ), MTS 3715 ( WTU-F-9293; holotype).