Rhodocollybia laulaha Desjardin, Halling et Hemmes, sp. nov.
Pileus 30-80 (-190) mm latus, campanulatus vel convexo-umbonatus, deinde plano-convexo, centro late umbonatus, margine estriatus, hygrophanus, glaber, initio pallide brunneus, dein pallide brunneo-aurantiacus vel aurantio-albidus. Lamellae adnexae vel sinuatae, densae, angustatae, anastamosae, labyrinthiformae, constrictae prope stipe, pallide aurantio-albae. Stipe 30-80 X 5-7 mm, centralis vel eccentricus, terete vel compressus, cylindricus vel clavatus, striatus, pruinosus, basi glaber vel tomentosus, pallide aurantio-albidus vel pallide brunneo-griseus, rhizomorphis albidus vel pallide roseus. Basidiosporae 5.5-7.0 X 3.5-4.5 µm, ellipsoideae, leves, hyalinae, cyanophilae, raro dextrinoideae. Basidia 17.5-22.5 X 7.5-8.5 µm, 4-spora. Cheilocystidia numerosae, 19-58 X 3-6 µm, contorto-cylindracea vel sinuosae, raro catenulatae. Pleurocystidia nulla. Hyphae pileipellis 2.5-5.5 µm latae, cylindraceae, cellulae terminalis versiformis, 40-80 X 5.5-16 µm, cylindraceae vel lageniformia, leves vel incrustatae, hyalinae, fibulatae. Caulocystidia numerosae, 38-100 X 4.0-8.0 µm, cylindraceae vel subsinuosae, cheilocystidia similia. Fibulae praesentes. Solitarius vel cespitosus in silvis montanus. HOLOTYPUS: Hawai`i, Hawai`i Volcanoes National Park, Pu`u Pu`uai, along Devastation Trail, 4 Aug. 1993, D. E. Desjardin 5873 (SFSU; ISOTYPUS: BISH, NY).
Pileus (Figs. 1, 2, 7) 30-80 (-190) mm diam, campanulate to convex-umbonate when young, expanding with age to broadly convex or broadly campanulate, typically retaining a broad, low umbo, finally plano-convex-umbonate, often with a shallow depression surrounding the umbo; margin at first with inrolled margin, becoming decurved or sometimes uplifted in age, even to wavy, often eroded, split or lobed at maturity, non-striate; surface, dull, moist to lubricous, hygrophanous, smooth to rugulose or undulate, glabrous; when young light brown to brown (7D E4-5) overall, remaining so in splotches or fading overall with age and moisture loss to light brown (6D4-5; "ochraceous tawny"), light brownish orange (6C4-5), pale brownish grey (6C3), or paler to greyish orange (5B3-5; 6B5), finally fading to orange white (5A2-3), pale yellowish white or cream buff (4A2-3), often with brown to pale reddish brown spots scattered over the pileus. Context 5-10 mm thick at the disc, 1-3 mm thick from stipe to margin, white to buff, soft. Lamellae shallowly adnexed or sinuate, extremely crowded with 3-5 series of lamellulae, narrow (1-4 mm), anastomosing and laybrinthine near the stipe, often forked, with a circumsessile constriction approx. 5-13 mm away from the stipe; edges minutely fimbriate to eroded, concolorous with the sides; pale orange white (5A2) when young, becoming dingy greyish orange (5-6B-C3) in age, sometimes spotting pale reddish brown (like the pileus) in age or where bruised. Stipe (22-) 30-80 X 5-7 (apex) X 6-20 (base) mm, central to strongly eccentric, terete to compressed, variable in shape from ±equal to apically flared, or with a clavate to subbulbous base, sometimes tapered below the bulb (i.e., fusoid), longitudinally ridged or striate, stuffed to hollow, tough; surface dull, dry, pruinose to canescent or appressed-downy above, glabrescent, base glabrous or minutely tomentose; pale orange white (5A2) to pale reddish white (6-7A2) when young, becoming pale brownish grey (6C3-4) in age, sometimes spotted as on pileus; often arising from coarse (0.5-1.5 mm diam), branched, white to pale pinkish buff rhizomorphs. Odor mild to strong, sweetly fungal; taste bitter, unpleasant.
Basidiospores (Fig. 8) (5.3-) 5.5-7.0 X 3.5-4.5 µm [range of means = 6.2-6.5 X 4.0-4.1 µm, mean of means = 6.35 ± 0.12 X 4.1 ± 0.04 µm, Q = 1.4-1.8, range of Q means = 1.52-1.59, mean of Q means = 1.55 ± 0.03, n = 20-25 spores per 5 collections], ellipsoid, smooth, thin-walled, cyanophilous, a small percentage dextrinoid; spore deposit cream (4A3) to pale pinkish buff (5A3). Basidia (Fig. 9) 17.5-22.5 (- 28) X 7.5-8.5 µm, clavate, 4-spored, clamped. Basidioles (Fig. 9) clavate to subclavate (not subacerose). Pleurocystidia absent. Cheilocystidia (Fig. 10) abundant, lamellar edge sterile, 19- 58 X 3-6 µm, contorted-cylindrical to sinuous, obtuse, rarely in chains of 2-3 cells, seldom apically lobed, non-diverticulate, thin-walled, hyaline. Pileipellis a cutis of two layers: 1) epicutis a very thin layer of loosely interwoven hyphae 2.5-5.5 µm diam, cylindrical, branched, seldom with broad outgrowths but not diverticulate, non-incrusted, hyaline, overlaying a thick subcutis; 2) subcutis of repent, subparallel, radially arranged hyphae 4.5-12 µm diam, cylindrical, often slightly inflated at septa, non-diverticulate, smooth or more commonly with amorphous to subannular incrustations; walls thin, hyaline to pale yellowish brown. Terminal cells of pileipellis elements (Fig. 11) versiform, 40-80 X 5.5-16 µm, repent to erect, cylindrical to lageniform or obclavate, smooth overall or basally incrusted, hyaline. Pileus trama loosely interwoven, monomitic; hyphae 5.5-14 µm diam, cylindrical to slightly inflated, non-incrusted, hyaline, thin- to thick-walled (up to 0.5 µm). Hymenophoral trama regular; hyphae 80-200 X 4-8 (-12) µm, similar to pileus tramal hyphae. Stipe tissue monomitic; cortical and medullary hyphae undifferentiated, 5-12 µm diam, cylindrical, thin-walled, hyaline. Stipitipellis a loosely organized trichodermium of erect to suberect caulocystidia; caulocystidia (Fig. 12) abundant, 38-100 X 4.5- 8.0 µm, cylindrical to subsinuous, obtuse, similar to the cheilocystidia. All tissues inamyloid, non-gelatinous, clamped.
Habit, habitat and distribution. Solitary to gregarious, sometimes cespitose, in pumice or leaf litter, or on moss-covered logs or very rotten logs of hapu`u [Cibotium spp.; Dicksoniaceae], ohi`a [Metrosideros polymorpha Gaud.; Myrtaceae], koa [Acacia koa A. Gray; Fabaceae], kopiko [Psychotria hawaiiensis (A. Gray) Fosb.; Rubiaceae], or kolea [Myrsine lessertiana A. DC; Myrsinaceae] in Montane Wet Ohi`a Forest, Montane Wet Ohi`a/Hapu`u Forest, Montane Wet Koa/Ohi`a Forest, Montane Mesic Forest and Lowland Mesic Forest; rarely on rotten wood of Eucalyptus spp. in Lowland Alien Forest or on rotten wood of tropical ash [Fraxinus uhdei (Wenzig) Lingelsh.; Oleaceae] in Montane Alien Forest. All months, most common between July and December. Kaua`i, Hawai`i, Maui.
Specimens Examined. U.S.A. HAWAII: Hawai`i, Hamakua Dist., Kalopa State Recreation Area near Honoka`a, 5 Aug. 1993, DED 5899; same location, 19 Mar. 1994, DEH 432; same location, 22 Jul. 1994, DEH 502; Hawai`i, Hawai`i Volcanoes National Park, Ola`a Forest, 5 Sept. 1989, DEH 003; same location, 10 Sept. 1992, DEH 068; same location, 20 July 1993, DEH 244; same location, 16 Nov. 1993, DEH 325; same location, 21 Jul. 1995, DEH 847; Hawai`i, Hawai`i Volcanoes National Park, Thurston Lava Tube, 28 June 1994, DEH 482; same location, 10 Jul. 1996, DEH 1163; Hawai`i, Hawai`i Volcanoes National Park, Pu`u Pu`uai, along Devastation Trail, 4 Aug. 1993, DED 5873 (HOLOTYPE: SFSU; ISOTYPE: BISH, NY); same location, 25 Jul. 1992, DEH 7.25.92; same location, 10 Sept. 1992, DEH 066; Hawai`i, Hilo Forest Reserve, 12 Dec. 1995, DEH 936; Hawai`i, NARS, Pu`u Maka`ala, N19°ree;29.072', W155°ree;16.140', 21 Jul. 1992, DEH 7.21.92; same location, 22 Aug. 1995, DEH 866; same location, 21 Aug. 1996, DED 6548 ; Hawai`i, Saddle Rd. at 21 mi kipuka, 23 Aug. 1994, DEH 530; Hawai`i, Saddle Rd. at 18.5 mi kipuka, 1000 steps site, N19°ree;40.710', W155°ree;19.778', 19 Jun. 1996, DEH 1101; same location, 20 Aug. 1996, B. A. Perry 056; Hawai`i, Saddle Rd. at 10.5 mi kipuka, 24 Sept. 1991, DEH 9.24.91; same location, 19 Jun. 1996, DEH 1102; Hawai`i, Waipahoehoe, 5 Sept. 1989, DEH 9.5.89. Kaua`i, Koke`e State Park, Kahuamaa Flat, N22°ree;09.024', W159°ree;38.391', 5 Jan. 1994, DED 5988; Kaua`i, Koke`e State Park, Kaluhapuhi Trail, N22°ree;08.530', W159°ree;38.750', 9 Jan. 1996, DED 6386; Kaua`i, Koke`e State Park, Milolii Ridge Trail off Makaha Ridge Rd., N22°ree;07.160', W159°ree;40.166', Oct. 1991, DEH 004; same location, 3 Oct. 1994, DEH 600; same location, 10 Jan. 1996, DED 6393; Kaua`i, Koke`e State Park, Pu`u Ka `Ohelo Berry Flat Trail, between N22°ree;07.158', W159°ree;38.725' and N22°ree;08.158', W159°ree;38.585', 8 Jan. 1996, DEH 952; Kaua`i, Kuia Natural Area Reserve, Nualolo Trail, N22°ree;06.309', W159°ree;40.603', 15 Jun. 1995, DEH 811. Maui, Kaumahina State Park, 14 Jun. 1992, DEH 6.14.92; Maui, Waihou Springs State Park, 22 Nov. 1996, DEH 1332.
Etymology. "laulaha": widespread.
Commentary. Rhodocollybia laulaha is characterized by the production of large basidiomes with campanulate to convex-umbonate pilei colored pale brown, greyish orange or orange white, extremely crowded and narrow lamellae that are labyrinthine and constricted near the stipe, a pale orange white, striate stipe, a bitter taste, and growth in native forests. Microscopically, the species is distinct because of the combination of small, ellipsoid basidiospores with imperceptably dextrinoid and conspicuously cyanophilous walls, sinuous cheilocystidia and caulocystidia, and a complex pileipellis. Rhodocollybia laulaha is the Hawaiian homolog to the north temperate Rhodocollybia maculata (Fr.) Singer. The Hawaiian species is closely allied with R. maculata var. fulva Lennox, described from Washington, but the latter differs in forming smaller (17--27 mm diam) and much darker pilei (dark vinaceous red to light fuscous vinaceous), non-labyrinthine and non-constricted, white lamellae, and a mild taste (fide Lennox, 1979).
Basidiomes of Rhodocollybia laulaha are one of the more commonly encountered mushrooms in montane native forests on the islands of Hawai`i and Kaua`i. Biweekly sampling over four years (by DEH) in several native forests on Hawai`i indicate that the species has a very predictable cycle for basidiome production. Basidiomes first appear profusely in July and continue abundant production through December. Throughout the remainder of the year, basidiomes are rarely formed even if the environmental conditions appear optimal. We have observed some basidiomes remaining in fairly good, unputrefied condition for 3--4 weeks.
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