A new variety of Boletus luridiformis

A new variety of Boletus luridiformis

• Volume 10, Part 2, May 1996 A NEW VARIETY OF BOLETUS LURIDIFORMIS D.N. PEGLER & *A.E. HILLS The Herbarium, Royal Botanic Gardens, Kew, Richmond, S...

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Volume 10, Part 2, May 1996

A NEW VARIETY OF BOLETUS LURIDIFORMIS D.N. PEGLER & *A.E. HILLS The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE *16 Acremead Road, Wheatley, Oxfordshire OX33 1NZ There are several species of Boletus Dill.: Fr. Section Luridi Fr. with a red hymenophore, growing in deciduous woodland and associated with trees of the family Fagaceae, such as Castanea Mill., Fagus 1. and Quercus L. Most are characterised by the presence of a conspicuous reticulate ornamentation on the upper stipe surface, a feature which typifies many species of Boletus s. str. Boletus luridus Fr. has a yellowish brown to reddish pileus and an orange to reddish brown stipe with a coarse, red reticulum, whilst both B. rhodoxanthus (Krombh.) Kallenb. and B. rhodopurpureus Smotl. have paler basidiomata and a purplish red reticulum. There are other red Boletus species, such as B. dupainii Boud., B. luridiformis Rostk. and B. queletii Schulzer, however, which either never have the reticulated ornamentation (which is replaced by a fine, granular-squamulose orna-

mentation), or occasionally have slight reticulation confined to the stipe apex (Singer, 1966). Boletus dupainii, an essentially Mediterranean species, and B. queletii have a yellowish stipe and ochraceous orange to scarlet red pileus, whilst B. luridiformis is more deeply pigmented with a brown pileus and a dark reddish stipe. In addition, B. luridiformis, a common species of British deciduous woods, is characterised by a bright yellow context and the surfaces of the basidioma, together with the context, discolour an intense deep blue on bruising or exposure. This is the species widely known as B. erythropus (Fr.: Fr.) Alessio, which was based upon an original description by Persoon. However, it was shown by Rauschert (1987) that Persoon's account represented B. queletii so that the next available name has to be adopted, namely B. luridiformis. During the autumn months of 1994 and 1995, one of the authors (AEH), has observed over thirty basidiomata, closely resembling those of B. luridiformis, in which the blue discolouration is totally lacking. This persists even after the context has been exposed for several hours. In addition, the surface pigmentation is somewhat darker than that found in typical B. luridiformis and continues to darken as the basidioma matures. As these striking differences have been observed on numerous occasions and remain constant from one season to the next, it is proposed to describe a new variety of B. luridiformis, as follows: 4 cm

Boletus luridiformis Rostk. var, immutatus Pegler & Hills, var. nov. Plate 1 A - D; Fig. 1 A - E

A typo carne immutato, basidiome Fig 1 Boletus luridiformis var. immutatus. A, Basidiomata and section; B, spores; non contuso et pigmentis profundis differt. C, basidia; D, cheilocystidia; E, trichodermium.

Volume 10, Part 2, May 1996 Pileus 2 - 12 em diam, at first hemispherical becoming strongly convex to pulvinate; surface dark brown, 'Bay' (Ridgway, 1912) (Munsell1YRj 3.0j 3.8) to 'Chestnut' (M.2.5YRj 3.0j 5.0) or 'Mahogany Red' (M.1YRj 3.7j 6.0), not bruising at any stage, velutinate to tomentose, dry, matt, glabrescent with age; margin acute, slightly exceeding the hymenophore. Hymenophore depressed, free to adnexed, deep red, 'Scarlet' (M.9Rj 4.9/ 14.0) to 'Morocco Red' (M.9.5j 3.2j 6.5), not bruising, poroid; tubes up to 14 mm long, sulphur yellow to yolk yellow, not bluing; pores small, 3 - 4 per mm, circular to polygonal. Stipe robust, 8 - 9 x 2 - 4 em, strongly ventricose (-7 em diam), with a tapering base; hard and solid; surface initially pale yellow at apex but soon deep red, 'Carmine' (M.5Rj 3.2j 11.5) to 'Snuff Brown' (M.7.5YRj 4.5j 4.1), darkening with age, strongly speckled with minute, dark reddish granules, lacking any reticulum, not bruising except for some discolouration to dark reddish purple at the base. Context up to 1.5 em thick at the disk, 'Lemon Chrome' (M.5Yj 8.0j 11.5) to 'Lemon Yellow' (M.8Yj 8.2j 9.5), firm, unchanging except at the stipe base which slowly discolours deep reddish purple on exposure; consisting of inflated generative hyphae, 2 - 6 [lm diam, inflating to 16 [lm diam, thin-walled or occasionally with a slightly thickened wall, lacking clamp-connexions; Chemical reactions: potassium hydroxide: buff; ferrous sulphate: immediate blue-grey reaction; Odour rubbery; Taste mild. Spores 9.5 12.5 x 4.5 - 5.5 (11.2 ± 0.9 x 4.8 ± 0.3) [lm, Q = 2.30, cylindrico-fusoid, brown, thick-walled, smooth, with prominent oil-guttules. Basidia 45 - 55 x 9 - 11 [lm, inflated clavate, bearing four sterigmata. Cystidia sparse to infrequent, 45 - 55 x 8 - 10 [lm, fusoid to mucronate, hyaline, thinwalled. Hymenophoral trama bilateral, hyaline, consisting of thin-walled, diverging hyphae, 1.5 6 [lm diam, lacking clamp-connexions. Subhymeniallayer 10 - 22 [lm wide, loosely interwoven. Pileipellis a trichodermium of hyaline, sinuous, cylindric elements, 35 - 70 x 2 - 4 [lm, thin-walled, with an obtuse apex. Specimens examined: Berkshire, Windsor Great Park, amongst mown grass under Quercus, 2 Sept. 1994, Hills, K(M)31766; under Fagus, 29 Sept. 1994, Hills; 6 Oct. 1994, Hills, K(M)31768; 16 Oct. 1995, Hills, K(M)31172, holotype; 20 Oct. 1995, Hills, K(M)31771, K(M)31772; 24 Oct. 1995,

Fig 2 Boletus luridiformis var. immutatus, mature basidioma.

Fig 3 Section through a basidioma to show the unchanging lemonyellow context.

Hills, K(M)31765, K(M)31767; 31 Oct. 1995, Hills, K(M)31774. The initial collection (2 September 1994) was a solitary basidioma, but nine were found in close proximity on 29 September, and 15 over a distance of about 2 km", The spores of typical B. luridiformis are usually quoted with greater dimensions, 14 - 16.5 x 5 - 6 [lm, than those found in var. immutatus but further observations will be required to confirm this as a constant character. References Munsell, A.H. (1962) Book of Color. London: Hilger & Watts Ltd. Rauschert, R. (1987) Nomenclatorische Studien bei H6heren Pilzen III. Rohrlinge (Boletales). Nova Hedwigia 45: 501 - 508. Ridgway, R. (1912) Color Standards and Color Nomenclature. Singer, R. (1966) Die Rohrlinge II: 122. Verlag J. Klinkhardt.