Paragyrodon sphaerosporus

[ Basidiomycetes > Boletales > Paxillaceae > Paragyrodon . . . ]

by Michael Kuo

This fascinating mushroom is often considered rare by the mycological community, but for Tony Reichstadt in Minnesota it is anything but a rare find, since it pops up in huge numbers under a White Oak in his lawn. Tony threw me for a loop when he sent me a "What's this mushroom?" e-mail featuring the photos to the right. Is it a Suillus? Is it a Gyrodon? The mushroom shares features with mushrooms in both genera, but doesn't seem to fit neatly into either genus.

The mushroom has a partial veil, like many species of Suillus, but the veil is so thoroughly attached to the lower stem that it almost seems to create a volva, rather than a ring. It stains and bruises brown from head to toe, and its pore surface is odd--with large, angular pores but without the radial arrangement of Gyrodon or many Suillus species. It grows under hardwoods, unlike most Suillus species, but it prefers oaks--unlike Gyrodon merulioides, which is fond of Ash.

Tony dried some specimens of the mystery mushroom, and sent them to me. A peek at the spores confirmed their identity; Paragyrodon sphaerosporus is just about the only bolete with (nearly) round spores. It is fairly common in the Great Lakes region, where it frequently appears under oaks in lawns. Typically, there is a summer fruiting period and a fall fruiting period.

Paragyrodon sphaerosporus ("Suillus sphaerosporus" in older guides) is not listed as edible by any author I can find. However, Tony had tentatively tried a few bites by the time he contacted me, and since he had experienced no ill effects, I gave him the green flag to try eating more. He reports that the mushroom is "very good--on par with any firm, flavorful bolete."

Description:

Ecology: Presumably mycorrhizal; under hardwoods, especially oaks, in the Great Lakes region; typically fruiting in June and in September. According to Smith & Thiers (1971, p. 36), it is "one of the most frequently collected species in modern 'suburbia' [in Michigan] where original forest trees have been left as shade trees and the ground cover cleaned out but not planted to grass. It seems apparent that the fungus must have been living in the original forest, but did not fruit (or does not) as readily under those conditions as it does after the habitat has been changed."

Cap: 4-20 cm; convex becoming broadly convex or flat; sticky or slimy; smooth; yellowish at first, becoming brown; bruising dark brown; sometimes with partial veil remnants on the margin.

Pore Surface: Attached to the stem or beginning to run down it; yellow, becoming brownish with age; bruising promptly and strongly brown; pores angular, about 1 per mm, not radially arranged; tubes about 1 cm deep.

Stem: 4-10 cm long; 1-3 cm thick; more or less equal; fairly smooth near the apex; partial veil whitish to yellowish, attached near the base of the stem and eventually collapsing against it to form a sheathing ring; white to yellowish; bruising brown.

Flesh: White to yellowish; staining brown on exposure.

Odor and Taste: Not distinctive.

Chemical Reactions: Not recorded. On dried specimens I received red to pinkish reactions from all surfaces with the application of KOH; negative reactions with ammonia; and grayish reactions with iron salts. While distinctive, these reactions are not necessarily reflective of reactions that might be demonstrated on living material.

Spore Print: Dark yellowish brown.

Microscopic Features: Spores 6-9 x 6-8 µ; smooth; nearly round. Pleurocystidia 20-32 x 8-12 µ; fusoid-ventricose.

REFERENCES: (Peck, 1885) Singer, 1942. (Smith & Thiers, 1964; Smith & Thiers, 1971; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Both, 1993; Bessette, Roody & Bessette, 2000.) Herb. Kuo 10140401 (deposited in TENN).

Suillus sphaerosporus is a synonym.

Further Online Information:

Suillus sphaerosporus in Smith & Thiers, 1971
Paragyrodon sphaerosporus at Tom Volk's Fungi

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Cite this page as:

Kuo, M. (2004, November). Paragyrodon sphaerosporus. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/paragyrodon_sphaerosporus.html