Leccinum eximium (Peck) Singer, Persoonia 7: 319. 1973.
Pileus 3.58 cm broad, at first convex to plano-convex, with age plano-convex, dry to moist; disc even, at first violet brown, then chocolate brown; margin even, when young chocolate brown to violet brown, then chocolate brown; surface matted subtomentose to subvelutinous, becoming subtomentose to tomentose; sterile appendiculate flaps absent. Flesh 1020 mm thick, white with a grayish lilac tint to white with pale violet brown tint or pale lilac brown, staining absent; odor mild; taste mild. Hymenophore tubulose, adnexed to depressed. Tubes 510 mm long, rarely grayish yellow to light brown or brownish purple, becoming grayish brown to dark brown to purplish brown, unchanging when injured; pores 3 per mm, dark brown or purplish brown, then dark pinkish brown, brown when bruised. Stipe (4)615 cm long, 612(20) mm wide, equal to subequal, strict or curved, not radicating, dry; upper half when young finely scabrous, very pale violet, with age subpruinose to scabrous, very pale violet; lower half when young finely scabrous to scabrous, very pale violet, with age scabrous to finely scabrous or subscabrous ridged, very pale violet to lilac or lilac gray; scabers on upper half when young brown, with age brown, on lower half when young brown, with age brown; base white, staining not present. Stipe interior solid; flesh above when young pale violet brown to lilac brown, with age pale lilac brown to grayish lilac, staining not present; flesh at base when young grayish lilac to pale violet brown, with age pale lilac brown to grayish lilac, staining not present. Basal mycelium white.
Basidiospores vinaceous brown to pinkish brown, 10.513.3 µm long, 4.24.9 µm wide, mean Q = 2.55, smooth, ellipsoid to subfusoid to fusoid, inamyloid, with KOH pale brownish yellow. Basidia clavate, hyaline, 4 -sterigmate. Hymenial cystidia 2035 µm long, 68 µm wide, rare, thin walled, hyaline to golden colored contents, narrowly fusoid. Tube trama boletoid, hyaline, lateral strata elements 3.58.4 µm wide, with age subgelatinous. Pileipellis hyphae a trichodermium, in KOH yellow ochraceous, inamyloid; elements 3.56 µm wide, elongated to cylindric or obtuse, encrusted with pigment (but dissolving in KOH), thin walled, not gelatinized. Pileus trama interwoven, hyaline, inamyloid, thin walled. Stipitipellis hyphae vertically oriented, parallel, giving rise to clusters of caulocystidia, 2030 µm long, 514 µm wide, cylindric to clavate to subfusoid, hyaline to brown contents, with incrusting pigment present (with purple acerose crystals dissolving in KOH). Stipe trama hyphae parallel, cylindric, hyaline, inamyloid. Clamp connections absent.
Mycorrhizal host: Quercus.
The pale violet to lilac stipe with fine scabers, brown pileus with purple overtones, and brown hymenophore are distinctive local field characters. Because of the atypical stipe ornamentation (compare L. quercinum) and color of the spore deposit, some authors would place this taxon in Tylopilus. Originally described from the northeastern USA, L. eximium can be locally abundant in the Cordillera Central (Volcan Poas) and the Cordillera Talamanca. The Costa Rican material has a smaller stature and shorter spores (1013 µm) than the forms from the northeastern United States (1120 µm).
Cite this publication as: Halling, R. E., G. M. Mueller, and M. J. Dallwitz. 1998 onwards. Leccinum and Phylloporus in Costa Rica: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 13 Decmber 2006. http://www.nybg.org/bsci/res/hall/deltaindex.html. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993 onwards, 1998) should also be cited (see References).