|Major Groups > Boletes > Leccinum > Leccinum albellum|
Leccinum albellum (Peck) Singer, 1945
= Boletus albellus Peck, 1888
by Michael Kuo
Leccinum albellum is a slender, whitish species that is mycorrhizal with oaks and features, under the microscope, a pileipellis disposed as a trichoderm with inflated terminal elements. These characters are the deal breakers, and confusion with the superficially similar Leccinum holopus, which appears in wet birch woods and features a cutis, is thus easily avoided.
Ecology: Mycorrhizal with oaks--often with red oaks (section Lobatae of Quercus), and possibly also mycorrhizal with other hardwoods; frequently found in woods where oak is mixed with pines; appearing alone or gregariously in (June,) July, August, and September (October). Analysis of 64 collection records from online herbaria (see Figure 1) reveals only a few records in which oak is actually excluded by the collector's brief notes. A collection under bamboo (Guravich 1001 in MICH) may represent the collector's failure to recognize all potential mycorrhizal plants in the vicinity; a collection under paper birch (Dick, 1962, in BPI) may represent Leccinum holopus--especially if the pileipellis was not analyzed.
Distribution: Apparently widely distributed east of the Great Plains and especially common in the southeastern United States. Among the 64 collections found in online herbaria, only one was found outside this range, in Manitoba; I have excluded this collection on the assumption that it probably represents Leccinum holopus. Both (1993) includes "eastern Canada" in the range for Leccinum albellum, but the taxon is not included in Grund & Harrison's treatment of Nova Scotian boletes (1976), nor is it included in field guides (Barron, 1999; McNeil, 2006) for the region. Figure 2 represents the distribution of Leccinum albellum based on online herbarium collection locations--but I suspect that at least some collections from northern areas may actually represent Leccinum holopus.
Macromorphology: Pileus 2-7 cm; convex becoming broadly convex or plane; surface dry, very finely tomentose or glabrous; occasionally pitted or rugose-reticulate with brownish to grayish veins; whitish to pale grayish, pinkish, yellowish, pale tan, or olive; without a sterile margin. Context white or yellowish, especially in the stem; unchanging when sliced and exposed to air. Tubes to 1 cm long; whitish to grayish; pore surface whitish to grayish, becoming yellowish to olive buff, not bruising, depressed at the stipe; 1-2 round or angular pores per mm. Stipe 4-9 cm long; 5-12 mm wide; at maturity more or less equal or tapering to apex; whitish to pale olive or very pale gray; sometimes discoloring yellowish; finely scabrous with whitish to grayish or brownish scabers; basal mycelium whitish. Odor and taste not distinctive. Exsiccata with a dark brown pileus surface, a brown pore surface, and a yellowish brown stipe surface adorned with darker brown scabers. Spore print olive brown.
Chemical reactions: Iron salts purplish gray on context.
Micromorphology: Basidiospores (Figure 3) subfusoid; inamyloid; yellowish in KOH; smooth; 10-24 x 4-6.5 µ. Basidia clavate; four-sterigmate; up to 31 x 13.5 µ. Hymenial cystidia variously shaped but mostly fusoid-ventricose; up to 55 x 12 µ; hyaline in KOH; scattered to numerous. Pileipellis (Figure 4, Figure 5) a trichoderm of chained elements, the terminal elements subglobose or clavate, swollen to 15-30 µ wide; hyaline in KOH. Caulocystidia (Figure 4, Figure 6) in bundles with caulobasidia; variously shaped but mostly fusoid-ventricose with a long, twisted neck; also mucronate, subclavate, or irregular; up to 60 x 15 µ or longer; hyaline to grayish brown in KOH.
Molecular Data: Two partial sequences have been deposited in GenBank: AY612811 (partial 28S ribosomal RNA, deposited by T. Y. James et al. with a voucher of "TH6968" in an uncited herbarium), aligned by Binder & Hibbet (2004) and by den Bakker & Noordeloos (2005); and AY615910 (partial small subunit ribosomal RNA, mitochondrial, deposited by T. Y. James et al. with a voucher of "NCJ18" in an uncited herbarium), not aligned in any publication I am aware of. The Binder & Hibbett and den Bakker & Noordeloos alignments are similar, though not identical, placing AY612811 in a clade with oak- and hornbeam-associated taxa; in the den Bakker & Noordeloos alignment AY612811 is sister to a specimen identified as Leccinum carpini (syn. Leccinum pseudoscabrum); in the Binder & Hibbett alignment it is sister to a specimen identified as Leccinum rugosiceps.
The description of the caulocystidia above is, to my knowledge, the first for this taxon; it is based on 07241101, in my herbarium, and ASM 7388 in EIU. The skinny proportions of the fusoid spores may prove to be a feature with some value in separating Leccinum albellum from other taxa; the European treatment of Leccinum by den Bakker & Noordeloos (2005) found spore shape (not size) to have some predictive value in limited taxonomic areas.
References and Material Studied:
Collections Examined: PENNSYLVANIA: Kuo 07189200 & 07219200 (Indiana County). ILLINOIS: A. S. Methven 7388 (Clark County; EIU). NORTH CAROLINA: 07241101 (Buncombe County, M. Kessler).
Collection Notes Examined: D. Guravich 856 (Mississippi, 1977; micromorphology and det. N. S. Weber; MICH).
Field Guides and Online Treatments: Graham, 1944; Smith, Smith & Weber, 1981; Weber & Smith, 1985; Phillips, 1991/2005; Metzler & Metzler, 1992; Bessette, Roody & Bessette, 2000; Roody, 2003; Phillips, 2007.
Technical References: Singer, 1947; Smith, Thiers & Watling, 1967; Snell & Dick, 1970; Smith & Thiers, 1971; Both, 1993; Binder & Hibbett, 2004; den Bakker & Noordeloos, 2005. Full citations for these works can be found here.
Cite this page as:
Kuo, M. (2012, January). Leccinum albellum. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/leccinum_albellum.html