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Macrocybe titans

[ Basidiomycetes > Agaricales > Tricholomataceae > Macrocybe . . . ]

by Michael Kuo

There is a monster living in Florida. It is probably the largest gilled mushroom in North America, with a cap that can measure over a yard across. It regularly appears in urban areas, causing considerable amazement. Believe it or not, there are a dozen or so gilled mushrooms in the world that get this large, most of which belong in the genus Macrocybe--Latin for "huge head."

Macrocybe titans was originally described (as "Tricholoma titans") from grassy areas in northern Florida. Its defining features include the presence of bent-back scales on the stem, and, under the microscope, the presence of refractive pseudocystidia on the faces of the gills. (However, the scales are not always prominent, and the pseudocystidia can be difficult to observe.)

For a wonderful photo of Costa Rican Macrocybe titans specimens being sized up by mycologist Greg Mueller, see this page at the Field Museum's Web site. According to Pegler and collaborators (1998), the Costa Rican version of Macrocybe titans is unique in that it grows "from active Atta ant gardens" and has pseudocystidia on the edges (as well as the faces) of its gills.

Description:

Ecology: Saprobic; growing alone or, more often, gregariously or in clusters in grassy or sandy areas, or in ground disturbed by landscaping (usually in the year after the disturbance to the soil)--or, in Costa Rica, growing from ant colonies; fall and winter; common in Florida; tropical and subtropical in distribution.

Cap: 8-100 cm (that's up to one meter); convex, becoming broadly convex or flat; dry; smooth, but sometimes cracking in age or in dry weather; pale yellowish to brownish or buff, often with a pale cinnamon or yellowish center; fading with age to nearly white; the margin inrolled for quite some time.

Gills: Attached to the stem; very crowded; white to grayish or pale brown.

Stem: 6-35 cm long; 1.5-13 cm thick; equal or slightly swollen below; dry; whitish; often with small, bent-back, brownish to whitish scales by maturity.

Flesh: White; firm; not changing on exposure.

Odor: Fragrant or not distinctive.

Spore Print: Creamy.

Microscopic Features: Spores 5.5-7 x 4-5 µ; smooth; broadly ellipsoid, vaguely oval, or nearly round; inamyloid. Pseudocystidia scattered on gill faces; 35-50 x 7-10 µ; with refractive contents in KOH; fusoid to broadly fusoid, or with a long neck; often scarcely projecting. Clamp connections present and conspicuous.

REFERENCES: (Bigelow & Kimbrough, 1980) Pegler, Lodge & Nakasone, 1998. (Bigelow & Kimbrough, 1980; Pegler, Lodge & Nakasone, 1998; Halling & Mueller, 2004.) Herb. Kuo 10150702.

Tricholoma titans is a former name. Tricholoma cystidiosum of Mexico is a synonym.


Further Online Information:

Macrocybe titans at Macrofungi of Costa Rica



Macrocybe titans

 

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Macrocybe titans

Macrocybe titans

Macrocybe titans



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Cite this page as:

Kuo, M. (2010, May). Macrocybe titans. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/macrocybe titans.html