Gyrodon merulioides

[ Basidiomycetes > Boletales > Paxillaceae > Gyrodon . . . ]

by Michael Kuo

This odd bolete can be found in summer and fall wherever ash trees grow. It features an irregular brown cap, strongly "boletinoid" pores that are angular and widely spaced, and a stem that is almost always off-center, or even lateral.

Although it appears only under ash trees, Gyrodon merulioides is not actually mycorrhizal. Rather, it is involved in a symbiosis with Meliarhizophagus fraxinifolii, the "leafcurl ash aphid" (Brundrett & Kendrick, 1987). The mushroom'm mycelium forms little knots of tissue ("sclerotia") that surround and protect the aphid; in exchange the aphid's honeydew gives nutrients to the fungus. Meanwhile the aphid is busily doing damage to the ash tree.

Description:

Ecology: Found under white ash trees and other ash trees; probably involved in symbiosis with the leafcurl ash aphid, Meliarhizophagus fraxinifolii (see details above); growing alone, scattered, or gregariously; summer and fall; widely distributed in eastern North America (perhaps also in the southwest).

Cap: 5-20 cm, irregular (nearly convex when young, becoming wavy and nearly vase-shaped, or more or less flat); light to dark brown, sometimes reddish brown; dry, tacky when wet; soft and leathery; sometimes bruising darker brown.

Pore Surface: Pores elongated radially, sometimes appearing almost like gills, with many cross-veins; tubes shallow; running down the stem; yellow to olive, bruising brownish to olive to almost blue (sometimes not bruising); not easily separable.

Stem: 2-4 cm long; .5-2.5 cm thick; not central (sometimes nearly lateral); yellowish above, cap color or darker below; bruising darker brown.

Flesh: Whitish to yellowish; sometimes bruising slowly blue when exposed.

Odor and Taste: Not distinctive.

Chemical Reactions: Ammonia blackish, then reddish to orangish on cap surface; brown on flesh. KOH blackish, then reddish to orangish on cap surface; brown on flesh.

Spore Print: Olive brown.

Microscopic Features: Spores 7-10 x 6-7.5 µ; smooth; subglobose, or elliptical to ovate. Pleurocystidia to about 35 x 10 µ; lageniform. Pileipellis a cutis of mostly erect, cylindric elements 6-9 µ wide. Clamp connections present.

REFERENCES: (Schweinitz 1832) Singer, 1938. (Murrill, 1909; Coker & Beers, 1943; Singer, 1945; Snell & Dick, 1970; Smith & Thiers, 1971; Grund & Harrison, 1976; Smith, Smith & Weber, 1981; Brundrett & Kendrick, 1987; Phillips, 1991/2005; Lincoff, 1992; Metzler & Metzler, 1992; Both, 1993; Horn, Kay & Abel, 1993; Barron, 1999; Bessette, Roody & Bessette, 2000; Roody, 2003; McNeil, 2006; Miller & Miller, 2006; Kuo, 2007.) Herb. Kuo 09029501, 09190701.

Boletinellus merulioides is a synonym.

Further Online Information:

Boletinellus merulioides in Smith & Thiers, 1971
Boletinellus merulioides at Roger's Mushrooms

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Cite this page as:

Kuo, M. (2008, November). Gyrodon merulioides. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/gyrodon_merulioides.html