Russulales » Russulaceae » Lactifluus

Lactifluus pulchrellus F. Hampe & Wisitrassameewong

Mycobank MB818513

Basidiocarps small, fragile. Pileus 2–11.5 mm in diam, convex at first, then applanate, occasionally lobate; center at first sometimes papillate, later depressed; margin at first regular and bent downwards, later wavy; yellowish orange, bright orange, to orange reddish (5B7, 6C7–8, 6B8, 7D8), more intensive orange-red (8C–D8, 9C–D8) when young, often partially paler at maturity (6D6); surface velvety, dry, rimose and rivulose, sometimes with concentric cracks, at times striate almost up to the center. Stipe very small, 3–5 × 0.5–1 mm, equal, cylindrical or thickening towards base, velutinous, concolourous with the cap or somewhat more pinkish, base more pale, sometimes with fine white tomentum, immediately greenish blue with guaiac. Lamellae adnate, about 10–20 per pileus, moderately spaced with 1–3 lamellulae, relatively thick (1 mm); cream to yellow, staining brownish to brownish black (2F1) by the latex. Context 0.3–0.5 mm thick in the pileus, cream to pale yellow, not discoloring where bruised; taste mild. Latex abundant, watery greenish brown (2F3–5), staining lamellae and flesh brownish cream at first, then blackish (2F1), 30% KOH on latex yellow (4C7); taste mild. Spore print white. Basidiospores subglobose to broadly ellipsoid, 6.9–7.5–8.1 × 5.9–6.5–7.1 μm (Q = 1.07–1.17–1.28, n = 30); ornamentation amyloid, with irregular warts up to 0.3

μm high that are sometimes connected by fine lines, sometimes isolated; plage distally or almost completely and distinctly amyloid. Basidia 55–70 × 11–15 μm, 4- spored, sometimes 2-spored and then often with very long and irregular sterigmata. Pleuromacrocystidia 70–95 × 10–15 μm, cylindrical to subfusiform, often with rounded to slightly tapering apex, sometimes with long tapering apex, thin-walled. Pleuropseudocystidia 2–4 μm diam, cylindrical. Lamella edge sterile; cheilocystidia absent; marginal cells cylindrical to subclavate, thin-walled, and hyaline, 15–50 × 7–15 μm. Hymenophoral trama mixed, composed of hyphae and some small sphaerocytes. Pileipellis a lamprotrichopalisade with chains of short, irregular, or subglobose elements, with the terminal element of the chain clavate to globose and sometimes slightly thick-walled, mixed with long and rather slender distinctly thickwalled hairs; hair-like terminal elements up to 140 μm long, 12–14 μm diam, very thick-walled, often septate, usually tapering upwards. Clamp connections absent.

Ecology and distribution: On naked stony soil under Dipterocarpus tuberculatus. Thailand.

Notes: This is a striking species due to the small dimensions of the basidiocarps and the warm red to orange or even somewhat pinkish colors. The species stands out in Lactifluus sect. Gerardii, which has mainly dark brown to blackish brown or very pale to whitish representatives. Recently, Morozova et al. (2013) described a species in this section with deep orange tinges Lf. igniculus O.V. Morozova & E.S. Popov. They describe the species as pleurotoid, but the pictures in their description show agaricoid basidiocarps with a central to slightly eccentric stipe, which is macroscopically very similar to the proposed species here. However, the spore ornamentation differs considerably between the two species Lf. pulchrellus has low and irregular rounded warts, whereas Lf. igniculus has almost echinulate spores with acute warts up to 1.6 μm high (our own measurements), isolated or connected by fine lines. Morozova et al. (2013) also described a collection of Lf. aff. igniculus that is close to, but not conspecific with, Lf. igniculus. The basidiocarps look strikingly similar, and in the molecular analysis their ITS sequences only differ by a few base pairs from those of both Lf. igniculus and Lf. pulchrellus. Nonetheless, Lf. aff. igniculus differs morphologically from Lf. pulchrellus, with echinulate spores with warts up to 1 μm.