Calvatia fragilis

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by Michael Kuo

Calvatia fragilis is essentially a smaller version of the well known Calvatia cyathiformis. Like that species, it has purple-brown spore dust at maturity and, under the microscope, it features spiny spores. Calvatia fragilis differs, however, in its smaller size and in the fact that it lacks a substantial base section.

Some mycologists treat Calvatia fragilis as a mere form of Calvatia cyathiformis (officially, "Calvatia cyathiformis f. fragilis")--a position possibly supported by my collecting experience; several times I have collected the two "species" within a few feet of each other. However, I admit I have never found specimens that appear to "intergrade" between cyathiformis and fragilis; for this reason and out of deference to the Index Fungorum I am treating the taxa as separate species.

Description:

Ecology: Saprobic; terrestrial; growing alone, gregariously, or in fairy rings in grass--on lawns, in meadows, and so on; summer and early fall; widely distributed in North America but more common east of the Rocky Mountains.

Fruiting Body: Shaped like a ball, or nearly so; 4-9 cm wide and 3-8 cm high; whitish to brownish or purplish in places; with age the surface usually developing a mosaic pattern; flesh white, becoming yellowish and eventually turning to purple-brown spore dust; basal area lacking or extremely rudimentary (and then composed of cottony fibers).

Microscopic Features: Spores 4.5-7.5 µ; round or nearly so; spiny. Capillitial threads 2-10 µ wide; with pinhole pits.

REFERENCES: (Vittadini, 1842) Morgan, 1890. (Saccardo, 1888; Coker & Couch, 1928; Smith, 1951; Zeller & Smith, 1964; Smith, Smith & Weber, 1981; Kreisel, 1994.) Herb. Kuo 10310701, 07120803.

Further Online Information:

Calvatia fragilis in Smith, 1951

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Kuo, M. (2008, October). Calvatia fragilis. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/calvatia_fragilis.html