Sydowia 36: 283. 1983.
Common Name: none
Cap 4-11 cm broad, convex, in age plano-convex to plano-depressed, often with a low umbo; margin decurved to level, occasionally wavy; surface radially streaked with brown to grey-brown appressed fibrils, the disc darker, sparsely covered with a whitish to pale-tan tomentum (use hand lens); context white soft, unchanging, 5-10 mm thick; odor weakly rhapanoid, taste mild.
Gills free, close, whitish, maturing pinkish-brown, relatively broad, up to 10 mm in width, edges colored like the faces, fringed (use hand lens); lamellulae in up to five series.
Stipe 5-11 cm tall, 0.5-2.0 (3.0) cm in width, straight, solid, more or less equal to slightly enlarged at the base; surface whitish, fibrillose-striate, the fibrils becoming brown and conspicuous in the lower portion; context fleshy-fibrous, whitish, unchanging; partial veil absent.
Spores 5.5-8.5 (9.0) microns, oblong-ellipsoid to ovoid, slightly inequilateral in profile, smooth, thin-walled, hilar appendage inconspicuous, inamyloid, contents granular; spores pinkish-brown to salmon-brown in deposit. Pleurocystidia abundant, horned, typically two-pronged, the walls thickened near the apex.
Solitary, gregarious, to clustered on decaying conifer wood, sawdust, wood chips; fruiting along the coast during mid-winter; presumably present in the Sierra Nevada; common but often misidentified (see comments).
Pluteus pouzarianus is an example of a mushroom easily recognized to genus but a challenge to identify to species. Like all Pluteus species it is characterized by free gills that mature pinkish-brown, the lack of a partial or universal veil, and occurrence on lignicolous substrates. Unfortunately, the principal fieldmarks, a greyish-brown, appressed fibrillose cap and fibrillose-striate stipe, are common to several Pluteus species in California. Of these, Pluteus cervinus is the most similar. No single character distinguishes the two species, rather a number of characters are needed to make an identification. Typically the cap of Pluteus cervinus is more uniformly brown than that of P. pouzarianus which is often greyish-brown. A more significant difference is the nature of the cuticle. In Pluteus pouzarianus the cuticle is two-layered, the upper layer consisting of erect, nearly hyaline, hyphae over a lower strata of repent brown hyphae. The result is a cap disc that has a faint whitish bloom (use hand lens). Pluteus cervinus in contrast differs in possessing surface disc hyphae that are typically brown. Microscopically, Pluteus pouzarianus possesses clamp connections, these usually absent in P. cervinus. Finally, Pluteus pouzarianus has a weak rhaphanoid odor, compared to strong in P. cervinus. Pluteus atromarginatus, another brown capped species, is more easily identified because of dark gill edges, a feature not seen in Pluteus pouzarianus or P. cervinus. Adding to the above complexity, DNA sequencing by Vellinga suggests that what is called Pluteus pouzarianus and P. cervinus in the S.F. Bay area, does not match the European taxa on which species concepts are based, thus the taxonomy will likely have to be revised.
Bas, C., Kyper, T.W., Noordeloos, M.E. & Vellinga, E.C. (1990). Flora Agaricina Neerlandica -- Critical monographs on the families of agarics and boleti occuring in the Netherlands. Volume 2. Pluteaceae, Tricholomataceae. A. A. Balkema: Rotterdam, Netherlands. 137 p.
Desjardin, D.E., Wood, M.G. & Stevens, F.A. (2015). California Mushrooms: The Comprehensive Identification Guide. Timber Press: Portland, OR. 560 p.
Singer, R. (1983). Weiss-und rosasporige Agaricales (Tricholomataceae und Pluteaceae) österreich. Sydowia 36: 277-287.