Hortiboletus engelii Biketova & Wasser

Hortiboletus engelii (Hlaváček) Biketova & Wasser, Index Fungorum 257: 1 (2015) Figs 3 b, 8, 11, 12 ≡ Boletus engelii Hlaváček, Mykologický Sborník 78: 67 (2001) ≡ Xerocomus engelii (Hlaváček) Gelardi, Boll. Assoc. Micol. Ecol. Romana 24–25 (75–76): 18 (2009) [2008] ≡ Xerocomellus engelii (Hlaváček) Šutara, Czech Mycol. 60 (1): 49 (2008) = Xerocomus quercinus H. Engel & T. Brückn., in Engel, Dermek, Klofac, Ludwig & Brückner, Schmier- und Filzröhrlinge s. l. in Europa: 205 (1996), nom. inval., nom. prov., Arts 36.1 (a), 39.1, 40.1 (Shenzhen) ? = Boletus communis Bull., Herb. Fr. 9: tab. 393 (1789), s. auct. = Xerocomus communis (Bull.) Bon, Docums Mycol. 14 (56): 16 (1985) [1984], s. auct. = Ceriomyces communis (Bull.) Murrill, Mycologia 1 (4): 155 (1909), s. auct. = Boletus communis Sowerby, Coloured Figures of English Fungi 2: 94, pl. 225 (1799), nom. illeg., s. auct. ? = Boletus subtomentosus subsp. declivitatum C. Martín, Matériaux pour la Flore Cryptogamique de la Suisse 2 (1): 18 (1904), s. auct. = Boletus declivitatum (C. Martín) Watling, Edinb. J. Bot. 61 (1): 43 (2004), s. auct. = Xerocomus declivitatum (C. Martín) Klofac, Öst. Z. Pilzk. 16: 258 (2007), s. auct. Holotype. GERMANY • Thuringia: Gera, MTB 5138/1, Weinberg (vineyard), on the ground, 250 m, 1989, leg. T. Brückner. Description. Basidiomes pileate-stipitate, xerocomoid, epigeal, small to medium-small sized. Ontogenetic development gymnocarpic. Pileus (4 –) 5–13 (– 15) cm broad, nearly hemispherical at first, then convex, pulvinate to applanate, also slightly depressed at centre, sometimes irregularly shaped; surface matt, dry, ± finely tomentose to sometimes rugulose, finely areolate towards the peripheral zone or with minute to coarse cracks over the whole surface especially with dry weather and showing a yellowish or somewhat pinkish subpellis layer resembling some areolate Xerocomellus species (Simonini 1998 b); margin initially involute then extended or even uplifted, regular to wavy-lobed, acute and slightly exceeding the pileal context, whitish at the very beginning for a thin strip, but soon concolourous; of extremely variable colours, but generally dark brown up to black-brown at the beginning, then fading to ochraceous, ochraceous yellow, buff, yellowish-brown, olivaceous brown, greyish-brown, olive grey, grey or also pinkish-red, orange-red, ochraceous red, ochraceous pink, reddish-brown, typically fading in age, although some basidiomes maintain a carmine red tint over the entire life-cycle; unchanging or becoming slightly darker on handling or when injured. Tubes up to 15 mm long, at first adnate, later emarginate or slightly decurrent with a tooth, initially lemon or chrome yellow, later greenish-yellow to olive brown, unchangeable to weakly bluing when injured. Pores large, wider than 1 mm (up to 1.5–3 mm) in old basidiomes, roundish to angular, concolourous with the tubes, in mature basidiomes with orange-rusty spots, unchangeable to weakly bluing when bruised and later becoming dirty brownish. Stipe (2 –) 2.5–7 (12) × 0.6–3.5 (– 4.5) cm, usually as long as the pileus diameter or slightly longer, central or slightly off-centre, solid, firstly versiform, clavate or somewhat bulbose, later more or less cylindrical or sometime inflated in the lower part, not infrequently stout, bulbose to ventricose-subfusiform, always tapering at the very base and slightly rooting; surface with very fine fibrils or scales or, occasionally, very finely ribbed, which may be reddish on an ochraceous-yellow background or concolourous with the background, later often with rather coarse longitudinal striations; yellow at apex; sometimes the stipe can be entirely yellow, entirely red, or a mix of both colours; some basidiomes exhibit a thin, lemon-yellow cortex shaded of carmine red at base; unchangeable or very slowly bruising pale brown on handling; basal mycelium whitish-yellow, rarely bright yellow. Context rather firm when young, later soft in the pileus (up to 2.4 cm thick in the central zone, up to 1.0 cm thick halfway to margin and gradually becoming thinner towards the edge), becoming fibrous in the stipe; generally pale yellow, but dirty ochraceous yellow in the lower half of the stipe and eventually (especially in collections recorded late in the season and with low temperatures) reddish for a few mm underneath the cuticle, in the stipe base with a typical carrot-orange or orange-red pigment in the form of small dots (“ ponctuation de Redeuilh ”), which are sometimes scarce and hardly noticeable or conversely abundant (especially in dry conditions) and then visible as a large flame-orange area at the stipe base; light blue on exposure, especially in the pileus-stipe connection zone, above the tubes and in the peripheral layers of the stipe, later fading to dirty yellow; discoloration less pronounced in dry and old basidiomes. Spore print olive brown. Odour pleasantly fungoid to fruity or inconspicuous. Taste mild. Macrochemical spot-test reactions: Melzer’s reagent: a weak fleeting-amyloid reaction in the stipe context and exceptionally also in the hymenophoral trama of dried basidiomes sometimes occurs, but most collections show a strong dextrinoid reaction in all tissues; 20 % KOH: reddish-brown on pileus and hymenophore, pinkish on pileus context, bright orange on stipe surface and context and progressively darker downwards; 25 % NH 4 OH: none to pale yellowish everywhere; 10 % FeSO 4: sordid green everywhere, particularly on the hymenophore. Basidiospores [1691 / 62 / 61] (10.0 –) 12.1 ± 0.8 (– 14.2) × (4.7 –) 5.1 ± 0.3 (– 5.9) μm, Q = (2.04 –) 2.35 ± 0.13 (– 2.57), Vm = 171 ± 30 μm 3, inequilateral, broadly ellipsoid or fusiform to ellipsoid-fusiform in side view, narrowly ellipsoid to amygdaliform or subfusiform in face view, smooth under light microscope, apex rounded, with a short apiculus, usually with a weak to pronounced suprahilar depression and with a slightly pronounced adaxial swelling, moderately thick-walled (up to 1 μm), straw yellow to honey yellow in water and 5 % KOH, having one or two large oil droplets when mature, rarely pluri-guttulate, inamyloid and orthochromatic. Basidia [153 / 7 / 7] (22.9 –) 36.6 ± 5.4 (– 54.8) × (8.6 –) 11.3 ± 1.3 (– 15.2) μm, subclavate to clavate, predominantly 4 - spored, sterigmata (1.5 –) 3.2 ± 1.1 (– 5.0) μm long, hyaline to yellowish in 5 % KOH and containing concolourous oil guttules, without basal clamps; basidioles subcylindrical to faintly clavate, smaller than basidia. Cheilocystidia [18 / 2 / 2] (49.0 –) 69.8 ± 9.7 (– 85.8) × (7.7 –) 10.0 ± 2.2 (– 16.0) μm, scattered, slender, ventricose-fusiform, often with elongated straight or flexuous neck, with rounded tip, smooth, mostly hyaline to pale yellowish in water and 5 % KOH. Pleurocystidia [87 / 8 / 8] (39.1 –) 65.5 ± 13.6 (– 99.3) × (7.5 –) 10.3 ± 1.9 (– 15.9) μm, infrequent, slender, ventricose-fusiform, often with an elongated straight neck, with rounded tip, smooth, mostly hyaline to pale yellowish in water and 5 % KOH. Pseudocystidia not observed. Hymenophoral trama bilaterally divergent, intermediate between the “ Phylloporus - type ” and the “ Boletus - type ”: lateral strata consisting of poorly divergent, tightly arranged, non-gelatinous hyphae almost touching each other, hyaline to very pale yellowish in water and 5 % KOH; mediostratum consisting of tightly adpressed, non-gelatinous, parallel running hyphae; in Congo red, the mediostratum is slightly darker than the lateral strata. Pileipellis a physalo-palisadoderm consisting of moderately long, more or less cylindrical, septate hyphae; terminal elements [660 / 22 / 22] (24.7 –) 36.5 ± 11.0 (– 63.3) × (8.4 –) 11.3 ± 2.2 (– 17.3) μm, Q = (1.93 –) 3.47 ± 1.58 (– 7.46), versiform, mainly broadly cylindrical with rounded apex to cystidioid, sometimes also with elongated neck, but also slender, narrowly cylindrical, moderately clavate, slightly tapering towards the tip, utriform, acorn-shaped, apex mainly rounded-obtuse, but sometimes pointed, finely encrusted, more intensely and coarsely downwards (with fine granular or rarely zebra-like epiparietal encrustations), hyaline to yellowish in water and 5 % KOH; subterminal elements subcylindrical, clearly restricted at septa, equal or broader than terminal ones, more frequently and coarsely encrusted, yellowish-brown in 5 % KOH. Subpileipellis elements usually distinctly encrusted by a fine, yellowish, granular pigment (5 % KOH). Stipitipellis consisting of slender, subparallel, smooth walled, hyaline to pale-yellow hyphae in 5 % KOH, 4.5–6 (– 9) μm broad, caulohymenium hardly observable and not well developed; in the upper third of the stipe, infrequent bundles of clavate caulobasidia (25–35 × 8–13 μm), hyaline to yellow in 5 % KOH and broadly ventricose to spherical caulobasidioles with a thin neck, (8 –) 9–12 (– 15) μm broad are usually present; furthermore, finely encrusted, hyaline, cylindrical, broad terminal cells with a round tip, (8 –) 10–12 (– 14) μm, similar to those of the pileipellis appearing here and there. Stipe texture apparently not differentiated from the stipe trama. Lateral stipe stratum not observed. Stipe trama consisting of parallel running hyphae, 5.0–8.5 μm broad, ± hyaline in water and 5 % KOH, inamyloid; infrequent thromboplerous hyphae 6.0–8.5 μm broad are observed. Clamp connections absent in all tissues. Ecology and phenology. solitary, gregarious in small groups or even subcaespitose, growing on bare soil, on litter or in the grass, often in anthropogenic environments, shrublands, less frequently in undisturbed forests, under a large array of ectomycorrhizal broadleaved trees and shrubs, including preferably Quercus spp. (Q. cerris, Q. coccifera, Q. frainetto, Q. ilex, Q. incana, Q. robur, Q. petraea, Q. pubescens, Q. suber), Fagus sylvatica, Tilia spp. (T. cordata, T. platyphyllos), Carpinus spp. (C. betulus, C. orientalis), sometimes also Betula spp., Castanea sativa, Corylus avellana, Halimium