Pseudoboletus parasiticus
Description
Pseudoboletus parasiticus, previously known as Boletus parasiticus and Xerocomus parasiticus, is a rare Boletaceae mushroom found on earthballs (Scleroderma citrinum). Pseudoboletus parasiticus is one of the earliest-diverging lineages of the Boletaceae, after the clade comprising Chalciporus and Buchwaldoboletus. It has yellow/brown pores and may stain reddish.
The cap is hemispherical when young, later flat, yellowish-brown, or darker, and up to 5 cm in diameter. The flesh is pale yellow and the spores are olive. The stem is a pale yellow to olive. While edible, it is of poor quality.
Common names: Parasitic Bolete.
Mushroom Identification
Ecology
Parasitic on Scleroderma citrinum, which is mycorrhizal with hardwoods and conifers (but see the discussion above); most frequently found, in my collecting experience, when the host is growing in eastern hemlock bogs; growing alone or in small clusters; summer and fall; originally described from France, and widespread in Europe; in North America distributed fairly widely east of the Great Plains.
Cap
2.5–7 cm across; convex, becoming broadly convex; dry; suedelike; becoming cracked with age; yellowish-brown with a hint of olive; sometimes bruising reddish; margin rolled under when young.
Pore Surface
Yellow, becoming olive-yellow and, eventually, brown to reddish-brown; not bruising; xerocomoid; with 1–2 angular pores per mm; tubes 3–6 mm deep.
Stem
4–8 cm long; 1–2 cm thick; equal; often curved near the base; dry; solid; colored more or less like the cap; covered with fine brown aggregations of fibrils, often in chevron patterns; sometimes bruising reddish when handled; basal mycelium white.
Flesh
Pale yellow, turning slowly chrome yellow above the tubes and in the stem; reddish in the stem base.
Odor and Taste
Not distinctive.
Spore Print
Olive-brown.
Chemical Reactions
Ammonia red to pink on cap surface; negative on flesh. KOH orangish on cap surface; negative to orangish on flesh. Iron salts negative on cap surface; blue-gray on flesh.
Microscopic Features
Spores 13–21 x 4–6 µm; boletoid-fusiform; smooth; golden in KOH. Basidia 35–40 x 5–7.5 µm; subclavate; 4-sterigmate. Hymenial cystidia 50–75 x 7.5–15 µm; fusiform or lageniform, with a long neck; smooth; thin-walled; hyaline in KOH. Pileipellis a collapsing trichoderm; elements 5–7.5 µm; wide, smooth, hyaline to yellowish in KOH; terminal cells cylindric with rounded to subclavate apices. Stipitipellis a collapsing trichoderm; elements 3–8 µm wide, smooth, hyaline to yellowish in KOH; terminal cells ranging from cylindric with rounded apices to subclavate or fusiform. Caulohymenium not found.
Similar Species
Xerocomellus chrysenteron has a reddish stem, usually untapered.
History
In 1790 Jean Baptiste Francois (Pierre) Bulliard described this mushroom and gave it the scientific name Boletus parasiticus by which it was widely known until 1888, when Lucien Quelet transferred it to the genus Xerocomus, renaming it Xerocomus parasiticus. In 1991 the famous Czech mycologist Josef Šutara (born 1934), a renowned authority on boletoid fungi, redefined the Parasitic Bolete as Pseudoboletus parasiticus, which is now its generally-accepted scientific name.
Synonyms of Pseudoboletus parasiticus include Boletus parasiticus Bull., and Xerocomus parasiticus (Bull.) Quel.
The specific epithet parasiticus was chosen when mycologists thought that this bolete was parasitizing 'live' fruitbodies of the Common Earthball, Scleroderma citrinum.
Photo sources:
Photo 1 - Author: Lycaon (CC BY-SA 4.0)
Photo 2 - Author: Dave W (Dave W) (CC BY-SA 3.0)
Photo 3 - Author: Björn S... (CC BY-SA 2.0)
Photo 4 - Author: Lycaon (CC BY-SA 4.0)
Photo 5 - Author: Hans-Martin Scheibner (CC BY-SA 3.0, 2.5 Generic, 2.0 Generic and 1.0 Generic)
