Russulales » Russulaceae » Russula

Russula siamensis

Russula siamensis Yomyart, Piap., Watling, Whalley & Sihan

Index Fungorum number: IF 510806

Pileus 22 – 45 mm diam., convex when young, then plano-convex with a depressed centre to plane when mature, surface radially fibrillose, slightly viscid when moist, light greyish olive (197C) to yellowish grey (156A), darker at central, margin incurved when young and becoming decurved when mature, strongly striate. Lamellae 30 – 40 mm wide, adnexed to adnated, close to sub-distant, white (NN155B) when mature, bruising to pale brown, without lamellulae, edge entire. Stipe 25 – 50 × 8 –12 mm, central, cylindrical to subcylindrical, sometimes tapering towards base, surface longitudinally striate, white (NN155D) to yellowish white (156D). Annulus 1 mm thick, white (NN155B), membranous, loosening, discrete. Context thin, stuffed or hollow when mature in stipe, yellowish white, pale yellow with KOH orangish yellow with FeSo4. Taste slightly acrid. Odour slightly fruity. Spore print white. Basidiospores 7–8.5 × 5.5–6 μm (Q= 1.25 –1.27 – 1.42), sub globose to broadly ellipsoid, ornamentation compost of warty, strongly amyloid, up to 1 μm high. Basidia 35 – 45 × 6.5 – 8.5 μm, subclavate to clavate, with 4 spores, sterigmata 1.50 – 3.75 μm long. Pleurocystidia 32–66 × 7–9 μm, abundant, subcylindrical to cylindrical, clavate, lanceolate, thin-walled. Cheilocystidia 30 – 45 × 6.5 – 8 μm, abundant, similar to pleurocystidia. Lamellar trama composed of numerous sphaerocytes surrounded by connective hyphae; sphaerocytes globose to elliptical. Pileocystidia not observed.

 

Fig. 1 Phylogenetic tree of eight Russula specimens, one Lactarius specimen (indicated in bold), and some reliable best-hit sequences from GenBank database using Maximum Likelihood method. Number at the node indicates bootstrap values. Termitomyces microcarpus was used as an outgroup.