Hygrocybe waolipo Desjardin et Hemmes, sp. nov.

Pileus 20-35 mm latus, convexus vel late convexus, dein ad discum depressus vel perforatus, haud striatus, glaber vel adpressofibrillosus, haud squamulosus, siccus, atrogriseus vel ater. Lamellae emarginatae vel adnatae, subdistantes vel distantes, latae, albae vel pallide griseae, dein griseae. Stipes 40-55 X 8-17 mm, aequalis, fistulosus, striatus, glaber, atrogriseus vel ater. Odor nullus. Sporae 7.0-9.5 X 5.5-7.0 µm, ovoideae, haud constrictae. Basidia 30.5-46.5 X 7.0 8.5 µm, bisporigera et tetrasporigera. Pseudocystidia subfusiformia, 150-200 X 9-16 µm, pigmento brunneolo vel fulvo impleta. Lamellarum acies fertilis. Pileipellis cutiformis, ex hyphis 4-24 µm latis, cylindraceis, haud gelatinosis, pigmento griseobrunneolo incrustatis. Lamellarum trama regularis vel subregularis, cellulis fusoideis, 90-160 X 12-26 µm. Stipitepellis cutiformis. Fibulae praesentes. Holotypus: Hawai`i, Natural Area Reserve System, Pu`u Maka`ala, 26 Sep. 1994, D. E. Hemmes 587 (SFSU; Isotypus BISH).

Pileus (Fig. 37) 20-35 mm diam, convex when young, becoming broadly convex, convex depressed or convex-umbilicate at maturity, often perforated at the disc to expose the hollow stipe, non-striate; surface dull, dry, glabrous to radially appressed-fibrillose (not squamulose), radially streaked; dark grey to black overall, not discoloring reddish where cut or bruised. Context thin (up to 1 mm), dark grey, not discoloring reddish. Lamellae ascending to horizontal, emarginate to adnate with a short decurrent tooth, subdistant to distant with 2-3 series of lamellulae, convex, broad (5-12 mm), thick; white or pale greyish white when young, becoming grey in age, not discoloring reddish where bruised, black-pruinose when dried. Stipe 40-55 X 8-17 mm, central, cylindrical, ± equal, hollow, finely longitudinally striate, glabrous, dry, dark grey to black overall. Odor not distinctive; taste not recorded.
Basidiospores (Fig. 38) 7.0-9.5 X 5.5-7.0 µm [mean = 8.1 ± 0.7 X 6.1 ± 0.5 µm, Q = 1.2-1.5, mean Q = 1.32 ± 0.08, n = 25 spores], ovoid, inequilateral in profile, not constricted, with a prominent hilar appendix, smooth, hyaline, inamyloid, thin-walled. Basidia (Fig. 39) 30.5-46.5 X 7.0-8.5 µm, sterigmata up to 7 µm long, 2- and 4-spored, clavate, hyaline, clamped. Basidioles clavate. Hymenial pseudocystidia (Fig. 40) common on sides and edges of lamellae, 150-200+ X 9-16 µm (at broadest), elongate-fusoid, subcylindrical or irregular in outline, arising as terminal cells of oleiferous hyphae from hymenophoral trama, curving outward through the hymenium and projecting 16-48 µm, thin-walled, inamyloid, clamped; contents resinous, brown, brownish yellow or brownish grey. Lamellar edge fertile, lacking cheilocystidia. Pileipellis a cutis on disc and margin (no trichodermium observed); hyphae 4-24 µm diam, repent, cylindrical, nongelatinous, finely roughened or incrusted, greyish brown or olivaceous grey in 3% KOH, pigment intraparietal, a few hyphae with pigmented contents, some pigment soluble in KOH and H2O; pileocystidia absent, terminal cells typically undifferentiated from subtending cells, mostly repent, a few suberect but not clustered to form tufts. Pileus trama subparallel; hyphae 90-160 X 12-26 µm, inflated, fusoid, with some cylindrical hyphae interspersed, these 4-8 µm diam (tissue nearly sarcodimitic), nongelatinous, nonincrusted, thin-walled, inamyloid. Hymenophoral trama regular to subregular, hyphae similar to those in pileus trama; with brown oleiferous hyphae interspersed. Stipe tissue monomitic; cortical and medullary hyphae undifferentiated; hyphae 4-20 µm diam, parallel, cylindrical, nongelatinous, nonincrusted; with brown oleiferous hyphae interspersed. Stipitipellis a cutis similar to the pileipellis; caulocystidia absent. Clamp connections present in all tissues.
Habit, habitat and distribution. Scattered in soil among debris of hapu`u (Cibotium spp.) in Montane Wet Forest (Ohi`a/Hapu`u Forest). September. Hawai`i.
Specimen Examined. U.S.A. HAWAII: Hawai`i, Natural Area Reserve System, Pu`u Maka`ala, N 19°29.072', W 155°16.140', 26 Sep. 1994, DEH 587 (Holotype).
Etymology. "waolipo" - Hawaiian for "found in the dark depths of the forest."
Commentary. Diagnostic features of Hygrocybe waolipo include: black, convex umbilicate, glabrous pileus; grey lamellae that do not discolor reddish; dark grey striate stipe; ovoid basidiospores with mean = 8.1 X 6.1 µm (Q = 1.32); conspicuous brown hymenial pseudocystidia; and a cutis-type pileipellis. The new Hawaiian species belongs in subgen. Pseudohygrocybe M. Bon, sect. Coccineae Fay., subsect. Ovinae (Bat.) Arnolds, where it is closely allied with three other pseudocystidia-forming taxa, viz., H. ovina (Bull.: Fr.) Kühn. from Europe, Hygrophorus subovinus Hesler & A. H. Sm. from southeastern United States, and Neohygrocybe squarrosa Horak from New Zealand. The latter three species all differ from Hygrocybe waolipo in having pilei that are conico-convex to plano-convex and squamulose to squarrose (at least on the disc) with a trichodermial pileipellis. In addition, H. ovina differs in forming context tissues and lamellae that bruise reddish, in having a nitrous odor, and in narrower basidiospores measuring 7.0-9.5 X 4.5-6.0 µm (Q = 1.5-1.65) (fide Arnolds, 1990; Horak, 1968). Hygrophorus subovinus differs in forming lamellae that bruise reddish, in having a sweet, fragrant odor, a sterile lamellar edge with filamentous cheilocystidia, and in forming smaller basidiospores measuring 5.5 7.0 X 5-6 µm (mean = 6.8 X 5.6, Q = 1.2; Topotype SFSU!). In addition to pileus morphology and pileipellis anatomy differences, Neohygrocybe squarrosa differs in producing smaller basidiospores measuring 6.5-7.5 X 4.5-5.5 µm (fide Horak, 1990).
Hygrocybe waolipo is known at present from three basidiomes collected deep in a montane native forest. The species is considered by us to represent a native species, possibly endemic, with closest ties to the odorless, non-staining New Zealand species N. squarrosa.

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