Summary:
Section Celluloderma. Pluteus tomentosulus is recognized among Pluteus species by its white cottony cap. Other features include an umbo on the cap, free, crowded, broad, white gills, a white stem, and growth on wood. A form brunneus with brown cap and stem was described from south Siberia in Russia (Malysheva(1)). DNA sequencing of Pacific Northwest material matches material from the type location of Pluteus tomentosulus in eastern North America (D. Miller, pers. comm.). Morphological features need to be correlated.

Cap:
up to 6cm across, broadly umbonate, wavy edge; white; floccose [cottony], (Schalkwijk-Barendsen), 2.5-7.5cm across, conic to bell-shaped, becoming flat, umbonate; whitish tinged pinkish; cottony to woolly, (Barron), 3-10cm across, white; covered with tiny soft hairs, (Bessette), 3-10cm across, soon expanded-umbonate; white; dry, margin even, (Smith(6)), "pure white at first, finally tinged pinkish along the margin and yellowish over disc"; "dry and appressed-fibrillose, at least toward margin, more often densely minutely pubescent to furfuraceous, disc matted-fibrillose and appearing glabrous or in age breaking up into inconspicuous more or less appressed scales, sometimes subrimose along the margin", (Smith & Stuntz)

Flesh:
solid, fibrous strands in stem; white, (Schalkwijk-Barendsen)

Gills:
free, crowded, broad; white then pink, (Schalkwijk-Barendsen), free; white becoming pink (Barron), broad, crowded; white then pink, (Smith(6)), free, close, broad, (Smith & Stuntz)

Stem:
up to 4cm long and up to 1cm wide, bent, often twisted, separates cleanly from cap, some thickening at the base; white, (Schalkwijk-Barendsen), up to 10cm long by 0.8cm wide, white; with fuzzy surface, (Barron), 5-10cm x 0.4-1cm, equal, often with a slight bulb; fibrillose-striate, unpolished, bulb +/- tomentose, (Smith(6)), 6-11cm x (0.4)0.7-1(1.5)cm at apex, equal or clavate-bulbous, solid, often hollow in large specimens; white, upper part pinkish when old and base often yellowish; pruinose to densely pubescent overall at first, more or less appressed-fibrillose near base when old and longitudinally striate in upper part, (Smith & Stuntz)

Veil:
[absent]

Odor:
not distinctive (Smith & Stuntz)

Taste:
not distinctive (Smith & Stuntz)

Microscopic spores:
spores 5-7 x 4.5-6 microns, [presumably smooth] pleurocystidia lacking horns, (Bessette), spores 5-7 x 4.5-6 microns; pleurocystidia 60-95 x 10-20(25) microns, fusoid-ventricose, cheilocystidia similar to pleurocystidia, clavate to fusoid-ventricose, (Smith(6)), spores 5.5-7 x 5-6 microns, nearly round to broadly elliptic, smooth, wall slightly thickened; pleurocystidia abundant, 60-90 (100) x 12-30 microns, fusoid-ventricose with obtuse to rounded apices, thin-walled, colorless, smooth, cheilocystidia 34-52 x 9-16 microns, similar to pleurocystidia or smaller, some merely saccate to clavate; cap cuticle a layer of radial semidecumbent hyphae (free ends projecting) with terminal cells 60-120 x 4-6 microns, somewhat cystidioid tapering to an obtuse or subacute tip, clamp connections absent, (Smith & Stuntz)

Spore deposit:
pink (Barron)

Notes:
There are collections from BC at the University of British Columbia. The University of Washington has collections from WA, OR, MI, and NY. Schalkwijk-Barendsen says it has been reported from AB, SK, and MB.

EDIBILITY

unknown (Bessette)