Russulales » Russulaceae » Lactarius

Lactarius inconspicuus

Lactarius inconspicuus H.T. Le & F. Hampe

MycoBank number: MB811744; Facesoffungi number: FoF00637

Basidiocarps small to medium sized. Pileus 10−56 mm diam., convex-umbonate in immature specimens, becoming plano-convex with depressed disc; surface minutely rugulose, dry to slightly sticky, glossy when moist, brown (7E6) to dark brown (7F8) in center or at least on umbo, brown (6E−F6) to light brown (6D7) to brownish orange (6C−D6), paler and cream-colored at margin; margin estriate when immature, becoming striate with age, crenulate. Lamellae subdecurrent to decurrent, 1−3 mm broad, crowded, with 3−4 series of lamellulae, yellowish white (2A2), pale yellow (4A3) to light yellow (4A4), turning brownish orange (6B−C7, 7C−D6) to reddish brown (8E5) when bruised. Stipe 20−75 × 2−8 mm, cylindrical to tapering upwards; surface dry to moist, smooth, brownish yellow (6B−C6) to brownish orange (6C8−7C8) to brown (7E−F8), fistulose, whitish pruinose at base. Context 1−3 mm thick in pileus, pale cream to orange-white (5A2) to brownish orange (5C−D6); odor faint, like L. quietus or Pentatomidae bugs; taste mild. Latex abundant, watery white, slowly turning pale yellow on exposure, unchanging with 10 % KOH, pale yellow on white tissue paper, pale yellow on white handkerchief; taste mild. Macrochemical reaction on the context: light brown (5D4−D5) with 10 % KOH, grayish yellow (4B3) with FeSO4. Basidiospores typically subglobose to broadly ellipsoid, rarely globose, 6.1−6.9−7.4−8.0(−8.1) × 5.5−5.8−6.3−6.9(−7.0) μm; Q = 1.03−1.13−1.16−1.28 (n = 100); ornamentation amyloid, up to 1.3 μm high, consisting of blunt to subacute thick ridges forming an incomplete to almost complete reticulum; isolated warts common; plage inamyloid, sometimes slightly distally amyloid. Basidia 30−62 × 8−18 μm, mostly 4-spored, sometimes 2-spored, subcylindrical to subclavate, with fine granules and guttate contents. Pleuromacrocystidia abundant, 30−114 × 8−20 μm, protruding up to 30 μm, subcylindrical to subfusiform, with mucronate to moniliform apex, with needle-like contents and fine granules. Pleuropseudocystidia not protruding, 3−5 μm diam., tortuous to straight, cylindrical, with fine granules. Lamellar edge heterogeneous, consisting of basidia, cylindrical to subclavate marginal cells 15−36 × 8−17 μm and abundant cheilocystidia 30−52 × 8−18 μm, not protruding to slightly protruding up to 10 μm, subfusiform to fusiform, with mucronate to moniliform apex. Lamellar trama consisting of globose cells, septate hyphae and lactiferous hyphae. Pileipellis an ixotrichoderm, 100−120 μm thick, consisting of erect cylindrical hyphae, or sometimes, repent cylindrical hyphae.

Habitat: solitary to gregarious on soil in montane tropical forests, under Castanopsis armata.

Collections examined: THAILAND, Chiang Mai province, Doi Suthep-Pui national park, Sangasabhasri Lane to Huai Kok Ma Village, N18º48.62 E98º54.60, alt. 1145 m, 02/06/2005, LTH256 (GENT!, CMU!, SFSU!);−ibid., 30/05/2004, LTH098 (GENT!, CMU!, SFSU!);−ibid., 24/06/2005, LTH306 (GENT!, CMU!, SFSU!);−ibid., 24/06/2005, LTH307 (GENT!, CMU!, SFSU!);−ibid., 21/04/2011, KW003 (GENT!, MFLU!);−ibid., 05/07/2012, KW339 (holotype, GENT!, isotype, MFLU!); Chiang Mai province, Mae Taeng district, Bahn Mae Sae, 50 km marker on highway 1095, N19º14.59 E98º39.45, alt. 962 m, 03/06/2011, KW016 (GENT!, MFLU!).

Notes: This species has the general features of the subgenus but lacks any striking distinguishing characters. In the field this species is similar to L. tangerinus. A microscopic examination revealed that these species can be distinguished by: (1) larger pleuromacrocystidia in L. inconspicuus; (2) presence of a narrow mucus layer in the pileipellis in L. inconspicuous; and (3) higher basidiospore ornamentation in L. tangerinus.

Fig. 1 The obtained ML phylogeny based on ITS sequences. Names in boldface are new species. Names in blue are obtained from public databases. Bootstrap values and posterior probabilities are indicated if they exceed 50% and 0.85, respectively. The bar scale represents the expected number of nucleotide changes per site.