Mycotaxon 90: 70. 2004.
Common Name: none
Cap 1.0-3.0 cm diameter, at first broadly conic to campanulate, in age nearly plane with a low umbo; margin incurved, then decurved, striate-sulcate at maturity, occasionally wavy to upturned; surface dry, more or less glabrous, dark-brown to mahogany-brown at the disc, lighter toward the margin, blue to blue-green with 3% KOH; context thin, pallid; odor of mushrooms, taste somewhat acrid.
Gills narrowly attached, sometimes appearing free, pale-buff in youth, light-brown with age, relatively broad, up to 4.0 mm in width; lamellulae up to four seried.
Stipe 1.5-3.5 cm long, 1.0-3.0 mm thick, more or less equal, hollow to stuffed; surface furfuraceous to finely scaled, the ornamentation pallid, becoming brownish with age or handling, then matching the underlying ground color; whitish tomentum and sparse rhizomorphs at the base; partial veil absent.
Spores 3.0-4.0 x 3.0 µm, subglobose to broadly elliptical, smooth, relatively thick-walled, hilar appendage conspicuous, hyaline mounted in water, dextrinoid in Meltzer's reagent; spore deposit not seen.
Scattered or in small groups under Cupressus macrocarpa (Monterey cypress) and Sequoia sempervirens (redwood); fruiting in late summer from fog drip and after fall rains; rare.
Pseudobaeospora stevensii, like many "little brown mushroom, LBMs," requires a combination of characters to identify with certainty. Principal fieldmarks are a mahogany-brown to dark reddish-brown cap with a striate-sulcate margin, and a bluish-green cap reaction with 3% KOH. Distinctive microscopic features include a two-layered pileipellis with dextrinoid tissues and relatively small, dextrinoid spores. There are many smilar LBMs, but two species that are especially close mimics are Gymnopus villosipes and Gymnopus subpruinosus. They differ in having finely striate caps that lack a blue-green reaction with KOH, and pubescent rather than fufuraceous or squamulose ornamented stipes.
Desjardin, D.E. (2004). A new species of Pseudobaeospora from Calfornia. Mycotaxon 90: 69-76. (PDF—Protologue)
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.