Gymnopus subpruinosus (Murrill) Desjardin, Halling et Hemmes, comb. nov.
= Marasmius subpruinosus Murrill in Pennington, N. Amer. Flora 9: 266. 1915.
= Collybia subpruinosa (Murrill) Dennis, Trans. Brit. Mycol. Soc. 34: 449. (1951) 1952.
Pileus (Figs. 4, 18) 12-30 (-67) mm diam, convex to broadly convex, obtusely conic or campanulate, soon becoming broadly campanulate to plano-convex, with or without a small central papilla or umbo; margin decurved to horizontal, seldom uplifted at maturity, even to wavy, seldom cleft, conspicuously rugulose-striate or corrugate-sulcate to the disc; surface dull, moist to dry, subhygrophanous to hygrophanous, glabrous or minutely pruinose (with 14x hand lens); when young and moist dark reddish brown (8F5-7) or brown (7-8E5-8) overall, disc and striae remaining so in age, and fading elsewhere to greyish brown (6C-D3), becoming pale brownish orange (5C4), greyish orange (5B3-4), or dingy orange white (5A2) overall with moisture loss, most commonly with disc and striae brown to greyish brown and greyish orange elsewhere. Context very thin (<1 mm), dingy buff, rubbery-pliant, tough. Lamellae adnate to shallowly adnexed, horizontal, subdistant to distant with 3-4 series of lamellulae, narrow to moderately broad (1-4 mm), straight to slightly concave or convex, sometimes intervenose, buff or pale orange white (5A2) when young, becoming pale greyish orange (5B3), pinkish tan, or pale brownish grey (6-7E3) in age, sometimes mottled with reddish brown spots; edges finely pruinose when dried. Stipe 15-40 (-55) X (1.0-) 1.5-3.0 mm, central to slightly eccentric, terete, apex equal or slightly flared, base enlarged, equal centrally, tough, fistulose, dull, dry, pubescent to tomentose overall, vestiture buff to pale greyish orange; apex concolorous with the lamellae, base greyish brown (6C-D3), dark greyish brown (6E-F3) brown (7E5-7) or dark brown (7F4-7); sometime with coarse white rhizomorphs attached. Odor mild to strongly fungal, like Marasmius oreades; taste not distinctive.
Basidiospores (Fig. 19) 8.0-10.0 (-11.0) X 4.5-5.2 (-5.4) µm [range of means = 8.9-9.4 X 4.7-4.9 µm, mean of means = 9.1 ± 0.2 X 4.8 ± 0.08 µm, Q = 1.7-2.1, range of Q means = 1.87-1.91, mean of Q means = 1.89 ± 0.02, n = 20 spores per 6 collections], ellipsoid to amygdaliform, smooth, hyaline, inamyloid, acyanophilous, white in deposit. Basidia (Fig. 20) 30-36 X 7.5-8.5 µm, clavate. Basidioles (Fig. 20) subclavate (not fusoid or subacerose). Pleurocystidia absent. Cheilocystidia (Fig. 21) abundant, lamellar edge sterile, 25-80 X 5-16 µm, versiform, ranging from irregularly cylindrical or sinuous to clavate, cylindrical-capitate, ventricose, or sphaeropedunculate, rarely with a knobby outgrowth, often in chains of 2-3 cells, hyaline, thin-walled. Pileipellis a cutis with numerous, scattered pileocystidia; hyphae 4-6 (-8) µm diam, cylindrical, subparallel to slightly interwoven, radially arranged, non-diverticulate, smooth or more commonly heavily incrusted with annular to zebroid, yellowish brown to brown pigment deposits, non-gelatinous; pileocystidia (Fig. 22) 15- 80 X 5-12 (-22) µm, erect or seldom repent, similar to the cheilocystidia, ranging from cylindrical or sinuous to clavate, ventricose or sphaeropedunculate, hyaline, smooth, thin-walled. Pileus trama interwoven; hyphae 5-10 (-12) µm, cylindrical, smooth, hyaline, inamyloid, non gelatinous, thick-walled (0.5-1.0 µm). Hymenophoral trama regular; hyphae similar to those of pileus trama. Stipe tissue monomitic; cortical and medullary hyphae undifferentiated, 4-16 mm diam, cylindrical to slightly inflated, hyaline to pale yellow or golden, inamyloid, non-gelatinous, thin-walled. Stipitipellis composed of numerous erect caulocystidia; caulocystidia (Fig. 23) 60-120 X 2.5-10.0 µm, single or more commonly in clusters of 2-10 cells, irregularly cylindrical to sinuous, gradually tapered upward, obtuse, sometimes in chains of 2-3 cells, hyaline, inamyloid, thin-walled. Clamp connections common in all tissues.
Habit, habitat and distribution. Solitary to scattered on rotten twigs and logs of ohi`a [Metrosideros polymorpha], koa [Acacia koa] and karakanut [Corynocarpus laevigatus J.R. Forster & G. Forster; Corynocarpaceae] in Montane Wet Ohi`a/Koa Forest with scattered alien plants, or scattered in duff under introduced pines [Pinus taeda L.; Pinaceae] in Montane Alien Pine Forest. August to January. Hawai`i, Kaua`i. Maui.
Specimens Examined. JAMAICA. Cockpit Co., Troy & Tyre, 12-14 Jan. 1909, Murrill & Harris 947 (Holotype; NY). U.S.A. HAWAII: Hawai`i, Saddle Road Pine Grove, 6 Sep. 1994, DEH 549. Kaua`i, Kuia Natural Area Reserve, Nualolo Trail, N22°ree;06.309', W159°ree;40.603', 5 Jan. 1994, DED 5989; same location, 7 Jan. 1994, DED 6019; same location, 3 Oct. 1994, DEH 595; same location, 4 Jan. 1995, DED 6142 (NY, SFSU); same location, 8 Jan. 1996, DED 6363; same location, 24 Aug. 1996, DED 6554. Maui, Kula, 22 Nov. 1996, DEH 1333.
Commentary. Gymnopus subpruinosus is characterized by relatively small basidiomes with plano-convex, conspicuously rugulose-striate, brown pilei, subdistant, adnate, pale greyish orange lamellae, and pubescent to tomentose stipes with a pallid apex and greyish brown to brown base. Microscopically, the species is distinct because of the relatively large basidiospores and the exceedingly long, versiform cheilocystidia and pileocystidia that are often in chains of 2-3 cells. Gymnopus subpruinosus is allied with the north temperate species G. dichrous (Berk. & Curt.) Halling and G. subnudus (Ellis ex Pk.) Halling. Gymnopus dichrous differs in forming less conspicuously rugulose-striate pilei, in forming stipes with a tuberculate knob at the base, narrower basidiospores (3.0-4.5 µm diam), smaller cheilocystidia not formed in chains, pileipellis hyphae with scattered diverticula and fewer and smaller pileocystidia, and much shorter and thick walled caulocystidia (Holotype FH!). Gymnopus subnudus differs in forming cinnamon brown pilei, has a bitter taste, and forms narrower basidiospores (3.0-4.5 mm diam), much smaller cheilocystidia not formed in chains, and a pileipellis lacking conspicuous pileocystidia (Holotype, NY!). Both G. dichrous and G. subnudus are associated with hardwood debris in eastern North America. Among tropical taxa, G. subpruinosus is most closely allied with Collybia coracicolor (Berk. & Curt.) Dennis described from Cuba; however, the latter species differs in forming cinnamon brown, umbilicate pilei, crowded lamellae, a pruinose stipe with scattered caulocystidia, much smaller basidiospores (5.5-8.0 X 3.0-4.0 µm), and lacks conspicuous pileocystidia (fide Pegler, 1983). Our concept of G. subpruinosus, based on examination of the holotype specimen (NY!), differs from that of Pegler (1983; p. 160; Figs. 27a-c, pl. 3G). The protologue (Pennington, 1915) clearly states that the pileus is "rugose-striate....finely pruinose" (hence the choice of epithet) and the stipe "about 5 cm long". In addition, we measured the basidiospores as 8-10 X 4.5-5.2 µm. Pegler (1983) reports the pileus as "smooth and shiny, glabrous.... margin finely striate," the stipe as up to 12 cm long, and basidiospores measuring 6-8 X 3.5-4 µm. He does not report pileocystidia which are present on the holotype and Hawaiian material. We suspect that the material from the Greater Antilles determined by Pegler as Collybia subpruinosa represents a different species.
Gymnopus subpruinosus is a commonly encountered litter decomposer in montane native forests under ohi`a, koa and introduced karakanut along the Nualolo Trail at Koke`e State Park on Kaua`i.
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