Gymnopus luxurians (Peck) Murrill, N. Amer. Flora 9: 362. 1916.

= Collybia luxurians Peck, Bull. Torrey Bot. Club 24: 141. 1897.
= Collybidium luxurians (Peck.) Murrill, Mycologia 3: 169. 1911.

= Collybia compressiceps H. E. Bigelow, Rhodora 78: 124. 1976.

Pileus (Figs. 3, 13) (12-) 20-65 (-125) mm diam, convex to broadly conex when young, expanding with age to plano-convex or plane, seldom with a broad umbo or with a depressed disc, more commonly centrally applanate; margin at first incurved, even, smooth, soon becoming decurved, in age horizontal to uplifted, splitting, pellucid-striate to striate; surface dull to subshiny, moist and sublubricous to dry, subhygrophanous, glabrous to radially appressed-fibrillose and streaked; when young brown (7E5-8), dark brown (7F5-8) or dark reddish brown (8F5-8) overall, disc remaining so in age or fading slightly with moisture loss, margin fading to brown (7E5-6), light brown (6-7D4-6; "hazel"), or pale brownish yellow (5C5-6; "clay color"), finally becoming greyish orange (6B3), pale orangish white (5A2), tan or buff with moisture loss. Context 2-4 mm thick, white, non-staining. Lamellae horizontal, shallowly adnexed to sinuate, seldom adnate, close to subdistant with 2-4 series of lamellulae, moderately broad to broad (3-7 mm); edges pruinose, white; faces buff to dingy white at first, becoming pale greyish orange (5B3) at maturity. Stipe 20-60 (-75) X 3-6 (apex) X 5-18 (base) mm, central, terete or compressed, gradually enlarged downward to a clavate, broadly clavate or sometimes subbulbous base, conspicuously longitudinally twisted-striate, tough, fibrous, hollow, dull, dry, pruinose to finely pubescent overall when young, often centrally glabrescent in age, base with white to pale orange white (5A2) tomentum; white or buff overall when young, remaining so in age or base darkening to greyish orange (5-6B3); often with coarse, white rhizomorphs. Odor mild to strongly fungal; taste mild to slightly acrid.
Basidiospores (Fig. 14) (7.7-) 8.0-10.0 X 4.2-5.0 (-5.4) µm [range of means = 8.5-9.3 X 4.5-4.8 µm, mean of means = 8.9 ± 0.3 X 4.6 ± 0.15 µm, Q = 1.6-2.3, range of Q means = 1.8-2.0, mean of Q means = 1.92 ± 0.1, n = 15-20 spores per 8 specimens], ellipsoid to amygdaliform, smooth, inamyloid, acyanophilous, thin walled, pale cream in deposit. Basidia (Fig. 15) 22-27 X 6.5-8.0 µm, clavate, 4-spored. Basidioles (Fig. 15) subclavate. Pleurocystidia absent. Cheilocystidia (Fig. 16) abundant, lamellar edge sterile, 20-43 X 5-10 µm, versiform, ranging from irregularly cylindrical or contorted to clavate, ventricose or sinuous, seldom lobed or diverticulate, erect, suberect or repent, hyaline, thin-walled. Pileipellis a cutis of two layers (poorly differentiated in some specimens): epicutis 8-32 µm thick, hyphae 2.5-5.5 µm diam, cylindrical, subparallel, radially arranged, non inflated, non-diverticulate, non-incrusted or very weakly incrusted, hyaline to pale brown; subcutis 50-100 µm thick, hyphae 4-8 (-12) µm diam, cylindrical, radially arranged, heavily incrusted with annular to zebroid, brown to greyish brown pigments, not soluble and not turning green in 3% KOH. Pileus trama interwoven; hyphae similar to subcutis hyphae but paler and less incrusted. Hymenophoral trama regular; hyphae 4-12 µm diam, cylindrical, hyaline, non incrusted. Stipe tissue monomitic; cortical and medullary hyphae undifferentiated, 3-8 µm diam, cylindrical, non-incrusted, hyaline to pale yellow. Stipitipellis composed of numerous erect and often clustered caulocystidia. Caulocystidia (Fig. 17) 20-100 X 2.58.0 (-12.0) µm, irregularly cylindrical to sinuous, hyaline, thin-walled. All hyphae inamyloid, non-gelatinous, clamped.
Habit, habitat and distribution. In subcespitose to cespitose clusters, often in "fairy rings", in duff under casuarina [Casuarina equisetifolia L.; Casuarinaceae] in Coastal Casuarina Forests, or in soil, grass clippings or wood chips in horticultural areas often under monkeypod trees [Samanea saman (Jacq.) Merr.; Fabaceae]. June to February. Hawai`i, Moloka`i and O`ahu.
Specimens Examined. U.S.A. HAWAII: Hawai`i, Hilo, near State and Federal Bldgs., 27 Jun. 1996, DEH 1133; Hawai`i, Hilo, Lili`uokalini Gardens, 30 Oct. 1996, DEH 1286 (NY, SFSU); same location, 5 Nov. 1996, DEH 1295; Hawai`i, Hilo, Waiakea Village Resort, 6 Dec. 1973, J. Kliejunas nos. 37, 38, 39; Hawai`i, Hilo, Wailoa River State Park, 11 Jul. 1996, DEH 1166; same location, 20 Nov. 1996, DEH 1326; Hawai`i, Kapoho, 6 Aug. 1996, DEH 1199; same location, 7 Nov. 1996, DEH 1301; Hawai`i, MacKenzie Beach State Park, N19°ree;26.32', W154°ree;51.768', 3 Aug. 1993, DED 5865 (NY, SFSU); same location, 19 Feb. 1994, DEH 418; same location, 20 Sep. 1994, DEH 572; same location, 4 Jan. 1996, DED 6336; same location, 25 Jun. 1996, DEH 1120; same location, 19 Aug. 1996, DED 6516; same location, 7 Nov. 1996, DEH 1304. Moloka`i, Pala`au State Park, N21°ree;10.500', W157°ree;00.312', 13 Jan. 1996, DEH 997. O`ahu, Honolulu, Ho`omaluhia Botanic Gardens, 14 Sep. 1996, DEH 1237.
Commentary. Gymnopus luxurians is characterized by the following features: a brown to dark brown, convex, radially appressed-fibrillose pileus that fades to pale brown or buff with moisture loss; close to subdistant, broad, buff-colored lamellae; cespitose, basally inflated stipes that are white to buff-colored and conspicuously twisted-striate or ridged; relatively broad basidiospores (4.2-5.0 µm); and irregularly cylindrical to sinuous cheilocystidia and caulocystidia. Described originally from Alabama (Peck, 1897), G. luxurians is common in eastern North America. In the Hawaiian Islands, the species is quite common in Coastal Casuarina Forests where it is often found in large arcs or fairy rings (menehune rings in Hawai`i).

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