Lactarius gracilis Hongo, J. Jap. Bot.

Wisitrassameewong, Komsit, Nuytinck, Jorinde, Hampe, Felix, Hyde, Kevin D. & Verbeken, Annemieke, 2014, Lactarius subgenus Russularia (Russulaceae) in South-East Asia: 2. Species with remarkably small basidiocarps, Phytotaxa 188 (4), pp. 181-197 : 193-194

Lactarius gracilis Hongo, J. Jap. Bot. 32: 144. 1957. ( Figs 5 & 6E )

Pileus 9–27 mm diam., broadly convex to convex when young, turning to plano-convex or applanate with umbonate or papillate at center; surface smooth, dry to greasy, in some specimens with slightly minutely cracked center; margin inflexed margin, bearing floccose tufts of hairs in young basidiocarps which become scarcer with age, dark yellowish brown to orange, pale orange or grayish orange (5C4) towards the margin, typically darker color on center, fading with age or in dry condition; hairs at the margin of pileus orange white (5A2) to grayish yellow to grayish orange. Lamellae decurrent, close to crowded, with 2–3 series of lamellulae, 1–2 mm broad, orange white (5A2) in young basidiocarps and turning brownish orange (6C5–C6) with age; edge concolorous. Stipe 23–57 × 1–4 mm, mostly slightly tapering upwards, slender, hollow pith, orange, often a paler orange at apex, with orange white or pale orange strigose hairs at base. Context thin in pileus, 1 mm broad, grayish orange (5B3), unchanging with 10% KOH, grayish brown (6D5) with FeSO 4; smell like the European L. quietus ; taste mild. Latex milky or watery white, unchanging on exposure, unchanging on white paper, unchanging with 10%KOH; taste mild.

Basidiospore subglobose to ellipsoid; 7.0– 8.1–8.4 –9.4 × 5.9– 7.0–7.3 –8.3 µm, Q = 1.07– 1.15–1.16 –1.27 (n = 60); ornamentation amyloid up to 1.0 µm high, comprising of irregularly elongated ridges or warts interconnected by fine lines, forming an incomplete reticulum to subreticulum; isolated warts numerous; plage inamyloid to slightly distally amyloid. Basidia 48–57 × 14–19 µm, subclavate, mostly 4−spored, 1−or 2−spored present, consisting of granular or guttate contents; sterigmata 6–16 × 1.5–3 µm. Pleuromacrocystidia numerous, 69–107 × 10–20 µm, emergent, generally subfusiform to subclavate with mucronate or tortuous moniliform apex, occasionally subcylindrical with obtuse apex; with needle-liked or granular contents. Pleuropseudocystidia fairly abundant, 5–7 µm diam., aseptate, not emergent or slightly emergent, cylindrical with rounded apex, sometimes branched near apex. Lamellae edge sterile, consisting of marginal cells and cheilocystidia; marginal cells abundant, 12–39 × 10–16 µm, slightly emergent, mostly subclavate, with rounded apex; cheilocystidia scarce, 37–45 × 11–13 µm, not emergent, subfusiform with mucronate apex. Hymenophoral trama consisting of abundant rosettes of sphaerocytes and lactifers. Pileipellis a cutis, 100–130 µm thick, consisting of a dense layer of repent e, with a few erect hyphae and rare globose cells. Stipitipellis a cutis, 40–60 µm thick, consisting of parallel hyphae, underlying layer composed of globose cells and hyphae, 4–7 µm diam., septate, thin-walled.

Habitat: gregarious on soil between leaf litter, in montane broad-leaved forest dominated by the member of Fagaceae .

Studied material: THAILAND, Chiang Mai province, Muang district, Suthep sub-district, Doi Suthep-Pui National Park , Sangasabhasri Lane to Huai Kok Ma village , 1145 m elev., N18°48.62 E98°54.60, 27/4/2011, KW006 ( MFLU!, GENT!) ;− ibid., 26/5/2011, KW020 ( MFLU!, GENT!) ;− ibid., 2/7/2011, KW094 ( MFLU!, GENT!) ;− ibid., 2/7/2011, KW096 ( MFLU!, GENT!) ;− ibid., 2/7/2011, KW102 ( MFLU!, GENT!) ;− ibid., 5/7/2012, KW334 ( MFLU!, GENT!) , THAILAND, Chiang Rai province, Mae Fah Luang district, Mae Salong Nok sub-district, Doi Mae Salong , 1269 m elev., N20°16.90 E99°62.30, 30/5/2012, KW222 ( MFLU!, GENT!) ;− ibid., 13/7/2012, KW350 ( MFLU!, GENT!) , THAILAND, Chiang Mai province, Mae-On district, Huaikaew sub-district, Ban Mae Kampong , 1450 m elev., N18°51.43 E99°22.09, 3/6/2012, KW250 ( MFLU!, GENT!) ;− ibid., 15/7/2012, KW354 ( MFLU!, GENT!) , THAILAND, Chiang Mai province, Mae-On district, Mae Takraii national park, Thep Saded waterfall, 1150 m elev., N18°55.32 E99°21.31, 1150 m elev., 5/7/2012, KW340 ( MFLU!, GENT!) , THAILAND, Lampang province, Muangparn district, Chaesorn sub-district, along highway No. 1252, 1420 m elev., N18°55.50 E99°23.30, 14/6/2013, KW422 ( MFLU!, GENT!) .

Comment: L. gracilis has been described from Japan and China. The type collection was reported under Shiia from Japan (Hongo 1957). We generally found the species in rainforest dominated with the members of Fagaceae e.g. Castanopsis , Quercus and Lithocarpus . Wang (2007) suggested that the pellis structure consists of a layer of rounded cells. Our study found a cutis as pileipellis structure which is concordant to the study of Le (2007).

Figures

FIGURE 5. L. gracilis: a. basidiospore, b. basidia, c. lamellae edge, d. pseudocystidia, e. cheilocystidia, f. pleuromacrocystidia, g. pileipellis (a: KW096, b-f: KW330, g: KW334) (scale bar = 10 μm).

FIGURE 6: Basidiocarps; A–B: L. crenulatulus (Photo A: Todd Elliott), C: L. perparvus (Photo: Todd Elliott), D: L. glabrigracilis (Photo: Felix Hampe), E: L. gracilis (Photo: Felix Hampe)