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Species Information
Summary: Section Pluteus. Features include 1) a cap usually some shade of brown, that is dry or slightly viscid, radially fibrillose, with or without well-defined fine scales at the center, 2) free, crowded, white gills, 3) white stem usually with longitudinal brown or gray-brown fibrils commonly grouped to form distinct fine scales, 4) growth on well-rotted wood, 5) pinkish brown spore deposit, and 6) microscopic characters including metuloid pleurocystidia that are fusiform to narrowly utriform, with 2-4(6) apical hooks, and the absence of clamp connections. Pluteus exilis is the only species in the Pluteus cervinus group (which lacks clamp connections) documented to occur in the Pacific Northwest by the molecular and morphological study of Justo(4). The description is derived from Justo(4). White variants of Pluteus "are found regularly and could be confused with many other species" (Siegel(2)). The R. Morrison photograph attached shows the white and the usual color mushrooms growing side by side.
Pluteus exilis is known with certainty from Santa Cruz County in CA north along the coastal forests up into BC. Collections were examined from CA and WA, and collections from BC, WA, and CA included in the molecular study.
Gills: free, ventricose, up to 0.7cm broad, crowded; "white when young, later pink"; "with even, or white, flocculose edges"
Stem: 4.0-10.0(14.0)cm x 0.5-2.0cm, cylindric, with slightly widened base (up to 2.5cm wide); "white, usually with longitudinal brown or gray-brown fibrils, commonly grouped to form distinct squamules, rarely without fibrils"
Odor: "indistinct or earth-like"
Taste: similar to odor
Microscopic spores: spores 6.5-8.4(9.0) x (4.5)5.0-6.0 microns, elliptic, rarely oblong, sometimes oval "or slightly constricted in the middle"; basidia 4-spored, 20-35 x 7-12 microns, "clavate, some with median constriction"; pleurocystidia frequent all over gill faces, (55)60-100(115) x 13-30(35) microns, metuloid, "fusiform, narrowly fusiform or narrowly utriform", thick-walled (to 3 microns) with 2-4(6) apical hooks (usually entire), colorless; intermediate cystidia (near gill edge) "similar to the pleurocystidia but smaller and/or with thinner walls, a few irregularly shaped, without distinct apical hooks and/or with rounded apices; without a predominant morphological type"; gill edge sterile, cheilocystidia crowded, (15)20-75 x 10-25(30) microns, "(narrowly) clavate, spheropedunculate or narrowly utriform", colorless, thin-walled; cap cuticle a cutis, with terminal elements 60-120(145) x 8-17(30) microns, individual elements cylindric, "some strongly tapering towards apex, mostly filled with brown intracellular pigment, with thin, smooth walls"; stem cuticle a cutis, hyphae 5-20 microns wide, cylindric, colorless "or with brown intracellular pigment", "with thin, smooth walls"; clamp connections absent on cap cuticle hyphae, not observed in any other part of the fruitbody
Spore deposit: pinkish brown
Habitat / Range
single or gregarious, growing on well-decayed wood of hardwoods (Alnus - alder, Notholithocarpus - tanoak) or conifers (Picea - spruce, Pseudotsuga - Douglas-fir), September-January
Similar Species
Pluteus cervinus sensu stricto is very similar to Pluteus exilis but is not known to occur in BC, WA, OR, or ID. "Generally speaking P. exilis has a darker pileus and a more markedly squamose stipe than P. cervinus, but there is a significant level of overlap in these characters."[Latin names italicized]. The two are distinct in the molecular study: the three collections from Washington and the one collection from BC were Pluteus exilis and 23 of 27 California collections were also P. exilis. The four in California that were Pluteus cervinus were fruiting in the spring (29 February to 21 April) but more sampling would be required to know if that is significant, particularly since Pluteus cervinus from other areas fruited at several different times in the year. (Justo(4)).
