Hygrocybe pakelo Desjardin et Hemmes, sp. nov.

Pileus 10-15(-25) mm latus, semiglobatus vel convexus, dein campanulatus vel planoconvexus, pellucidostriatus, glaber, glutinosus, aurantiacus, ad discum olivaceus, oliveobrunneus vel aurantiacus, marginem versus aurantiacus. Lamellae late vel angustae adnatae, distantes, pallide aurantiacae. Stipes 15-30 X 2-3 mm, aequalis, glaber, glutinosus, apicaliter albus, alboluteus vel alboaurantiacus, deorsum aurantiacus. Odor et sapor nulli. Sporae 7.5-10.2 X 4.5-6.4 µm, ellipsoideae, haud constrictae. Basidia 36-52 X 7.5-9.0 µm, tetrasporigera. Cheilocystidia et pleurocystidia nulla, lamellarum acies fertilis. Pileipellis ixotrichodermiformis, 55-110 µm profundus, ex hyphis erectis, ramosis, cylindraceis, 16-68 X 1.5-3.5 µm, gelatinosis. Lamellarum trama subregularis, cellulis brevis, inflatis vel cylindraceis, 28-88(-100) X 5-16(-24) µm praeditum. Stipitepellis ixotrichodermiformis. Fibulae praesentes. Holotypus: Hawai`i, Saddle Rd. at 18.5 mi kipuka, 6 Dec. 1994, D. E. Hemmes 653 (SFSU; Isotypus: BISH).

Pileus (Fig. 25) 10-15(-25) mm diam, hemispheric, convex or obtusely conic when young, expanding to campanulate, broadly convex or plano-convex in age, pellucid-striate 1/4-3/4 of the radius; surface glabrous, glutinous when young, viscid in age; color variable, disc when young colored olive (4F4-5), olive brown (4E5-8) to yellowish olive brown (5D-E5-6) or deep orange (5 6A-B6-8) and lacking olive tones; margin when young concolorous with the disc or slightly paler; in age disc remaining olive or deep orange, or fading to yellowish olive (4C4-8) or orange (5A5 7), and the margin fading to greyish orange (5B4-5), greyish yellow (4B4-5) or light orange (5A4); drying pale orange overall. Context very thin (0.25-0.5 mm), concolorous with pileus surface. Lamellae ascending to horizontal, narrowly to moderately broadly adnate, sometimes with a short decurrent tooth, distant with 1-3 series of lamellulae, moderately broad (2.0-2.5 mm), thick, light orange (5A3-5). Stipe 15-30 X 2-3 mm, central, terete, equal or slightly enlarged at the base, glabrous, glutinous when young and fresh, becoming viscid in age; apex white, pale yellowish white (3A2-3), light yellow (4A4-5), pale orangish white (5A2-3) or light orange to orange (5A4-7), base orange (5A-B6-8). Odor and taste not distinctive.
Basidiospores (Fig. 26) 7.5-10.2 X 4.5-6.4 µm [range of means = 8.4-9.0 X 5.0-5.4 µm, mean of means = 8.7 ± 0.2 X 5.2 ± 0.1 µm, Q = 1.4-2.0, range of Q means = 1.59-1.78, mean of Q means = 1.67 ± 0.07, n = 20 spores per 7 collections], ellipsoid, not constricted, smooth, hyaline, inamyloid, thin-walled. Basidia (Fig. 27) 36-52 X 7.5-9.0 µm, clavate, 4-spored, seldom 1-, 2- or 3-spored, clamped. Basidioles clavate. Hymenial cystidia and pseudocystidia absent. Pileipellis an ixotrichodermium 55-110 µm thick; hyphae 16-68 X 1.5-3.5 µm, cylindrical, not constricted at septa, erect, often branched, embedded in a thick gelatinous matrix, hyaline to pale yellow, typically unclamped, seldom clamped or with false clamps. Pileus trama composed of hyphae 4-16 µm diam, cylindrical to inflated, subgelatinous, hyaline to pale yellow. Hymenophoral trama subregular; hyphae 28-88(-100) X 5 16(-24) µm, cylindrical to inflated or fusoid, nongelatinous, hyaline to pale yellow. Stipitipellis a lax ixotrichodermium similar to the pileipellis. Clamp connections infrequent.
Habit, habitat and distribution. Solitary in mosses over soil or among mosses on fallen hapu`u logs in Montane Mesic Forest (Ohi`a Forest) and Montane Wet Forest (Ohi`a/Hapu`u Forest). May to January. Hawai`i, Moloka`i.
Specimens Examined. U.S.A. HAWAII: Hawai`i, Saddle Rd. at 18.5 mi kipuka, N 19°40.691', W 155°19.425', 6 Dec. 1994, DEH 653 (Holotype); same location, 13 Jan. 1992, DED 5513; same location, 26 May 1993, DED 5717; same location, 10 Sept. 1994, DEH 554; same location, 8 Nov. 1994, DEH 637; same location, 20 Dec. 1994, DEH 672; same location, 31 Oct. 1995, DEH 909; Hawai`i, Saddle Rd. at 19 mi kipuka, N 19°40.550', W 155°20.180', 14 Nov. 1995, DEH 916; Hawai`i, Natural Area Reserve System, Pu`u Maka`ala, N 19°29.072', W 155°16.140', 25 May 1993, DED 5679; same location, 7 June 1994, DEH 460. Moloka`i, Kamakou Forest Preserve, Hanalilolilo Trail, N 21°07.554', W 156°54.882', 9 Jan. 1995, DED 6210; same location, 12 Jan. 1996, DED 6399.
Etymology. "pakelo" - Hawaiian for "to slip out of the hand like a slippery fish", referring to the glutinous pileus and stipe.
Commentary. There occur two distinct forms of H. pakelo in the Hawaiian Islands: 1) several populations in Montane Mesic Forest kipukas on Hawai`i with distinctly olive tones over deep orange on young pilei (the olive tones typically disappear with pileus expansion); and 2) several populations in Montane Wet Forests (one population on Hawai`i and one on Moloka`i) with deep orange pilei lacking olive tones throughout development. All Hawaiian populations form light orange lamellae and orange stipes. The deep orange, glutinous pileus and stipe of H. pakelo suggest alliance with sect. Glutinosae Kühner (= Gliophorus Herink), subsect. Insipidae (Henrink) M. Bon, while the olive tones on many pilei suggest placement in subsect. Psittacinae (Bataille) Arnolds. Hygrocybe pakelo is micromorphologically indistinguishable from Hygrocybe psittacina (Schaeff.: Fr.) P. Kumm. and H. perplexa (A. H. Sm. & Hesler) Arnolds, both from North America and Europe. Hygrocybe psittacina differs, however, in developing bright green, bluish green, blue, wine-red, flesh-colored or yellowish green tones in pileus and stipe, and in forming green, bluish or yellowish tones in the lamellae. Hygrocybe perplexa differs in forming dark brown, dark reddish brown, or dark brownish green pilei, lamellae with brown and yellow tones, and a stipe with brown, grey, or olive tones. Among members of subsect. Insipidae (Henrink) M. Bon, H. pakelo is most similar to H. aurantioviscida Arnolds, H. glutinipes (J. Lange) R. Haller, H. citrina (Rea) J. Lange, and H. vitellina (Fr.) P. Karsten. Hygrocybe aurantioviscida and H. glutinipes [accepted by most European authors as synonyms (Boertmann, 1995) but see also Arnolds (1990)] differ from H. pakelo in forming distinctly yellow tones on pileus and stipe (lemon yellow, egg-yellow, yellowish orange, chrome yellow), broadly adnate to subdecurrent lamellae, smaller and often constricted basidiospores, and in forming much longer hyphae in the hymenophoral trama. Although there is some controversy in Europe concerning the delimitations of Hygrocybe citrina and H. vitellina [cf., Orton (1965), Arnolds (1990) and Boertmann (1995)], nonetheless, the latter two species are distinctly different from H. pakelo in forming more intensely yellow basidiomes with subdecurrent to decurrent lamellae. If H. vitellina and H. luteolaeta Arnolds are considered synonymous as suggested by Boertmann (1995), then the latter taxon differs further from H. pakelo in forming a sterile lamellar edge composed of filamentous cheilocystidia.

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