Hygrocybe aff. minutula (Pk.) Murrill, North American Flora 9: 380. 1916 (ut Hydrocybe minutulus).

= Hygrophorus minutulus Peck, New York State Mus. Bull. 1(2): 9. 1887.

Selected Descriptions. Hesler and Smith (1963: 243-244).

Pileus (Fig. 22) 4-7 mm diam, convex to broadly convex, pellucid-striate; surface glabrous, viscid (but not glutinous); deep red (9B8) overall when young, disc remaining so and margin becoming orangish red (8A8). Lamellae horizontal, slightly adnexed to adnate, subdistant to distant, moderately broad (ca 1 mm), convex; white to pale orangish white when young, becoming orangish red at maturity. Stipe 10-15 X 0.5-1.5 mm, central, terete, equal, glabrous, viscid; apex deep red (9A8), base reddish orange (7A6). Odor not distinctive; taste not recorded.
Basidiospores (Fig. 23) (7.5-)8.0-9.0(-9.3) X 5.0-6.5 µm [mean = 8.4 ± 0.5 X 5.6 ± 0.5 µm, Q = 1.3-1.7, mean Q = 1.5 ± 0.1, n = 25 spores], ellipsoid, not constricted, smooth, hyaline, inamyloid, thin-walled. Basidia (Fig. 24) 28-33 X 8.0-9.5 µm, 4-spored, clavate, clamped. Basidioles clavate. Hymenial cystidia and pseudocystidia absent. Pileipellis a loosely interwoven ixocutis up to 80 µm thick; hyphae 4-12 µm diam, cylindrical to slightly inflated, not or slightly constricted at the septa, subgelatinous, hyaline, clamped; terminal cells 48-112 X 5-10 µm, cylindrical to subclavate, repent to erect. Pileus trama little differentiated from pileipellis; hyphae 4-20 µm diam. Hymenophoral trama subregular; hyphae 100-300 X 8-20 µm, elongate-fusoid to cylindrical, often tapered towards both ends, nongelatinous, hyaline, clamped. Stipitipellis an ixocutis similar to the pileipellis. Caulocystidia absent. Clamp connections present in all tissues.
Habit, habitat and distribution. Solitary in moss over soil or on ohi`a log (Metrosideros polymorpha) in Montane Wet Forest (Ohi`a/Hapu`u Forest) and Montane Mesic Forest (O`hia Forest). April, August. Hawai`i.
Specimens Examined. U.S.A. HAWAII: Hawai`i, Natural Area Reserve System, Kahaualea, N 19°26.732', W 155°07.300', 25 Apr. 1995, DEH 771; Hawai`i, Saddle Rd. at 19 mi kipuka, N 19°40.550', W 155°20.180', 20 Aug. 1996, DED 6530.
Commentary. This taxon is known from only three basidiomes collected at two sites under endemic trees in montane native forests on the island of Hawai`i. We suspect that the Hawaiian taxon is unique, but until further specimens are collected, we have tentatively determined the material as Hygrocybe minutula with which it shares the most similarities. The deep red, viscid pileus and stipe, small stature, relatively large and non-constricted basidiospores and short basidia are characteristic. The North American H. minutula differs slightly from the Hawaiian material in having broadly adnate to subdecurrent lamellae, and narrower basidiospores (4-5 µm).

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