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Species Information
Summary: Subgenus Phlegmacium. Features include 1) a whitish to pale yellowish brown or pale yellowish cap, 2) young cap surface that stains yellow when cut or bruised, 3) whitish, crowded gills, 4) whitish stem that sometimes becomes brownish or light purplish, 5) faint, mildly unpleasant or radish-like odor, and 6) verrucose, almond-shaped spores.
Cortinarius argutus has been documented by molecular methods from BC, WA, MT, Estonia, Finland, France, Hungary, and Sweden (Cripps(6)). The first accompanying photo is from mainland BC.
Cap: 3-8cm across, (hemi-)spheric, then flat-convex, sometimes slightly umbonate; "initially completely white, later somewhat brownish white"; "fibrillose, slightly viscid when young, later dry and often diffracted at disc"
Flesh: white but turns reddish and finally bluish black when strongly bruised or dried slowly
Gills: "adnexed to notched, somewhat broad, close to crowded, color white to pinkish cream at first (reported as pale purple in the description of C. argutus f. viscosoglutinosus but otherwise not observed), becoming yellowish white, pale dull yellow, brownish yellow, or milk coffee; edges even, paler in color", (Cripps, with Latin names italicized)
Stem: 5-11.5cm long, 0.8-3cm thick above, long, narrow, flared at apex, base 1-1.2cm thick, slightly swollen tapering to a dull point (slightly rooting); white to cream, sometimes becoming brownish, reddish brown or light purplish; lower surface with sparse fibrils from veil; exsiccatae with upper stipe and flesh bluish to grayish, (Cripps), one to two easily over-looked narrow bands of veil remnants low on stem, (M. Beug, pers. comm.)
Veil: "white, sometimes copious on young specimen, forming a distinct fringe" on the edge of young caps, ephemeral, leaving fibrils on the stem; "cortina whitish", (Cripps)
Microscopic spores: 9.6-11.1(12.2) x 5.2-5.9(7) microns, amygdaliform [almond-shaped] to narrowly amygdaliform, moderately verrucose, not dextrinoid; cap cuticle of "a thin gelatinous layer, with a moderately developed, yellowish epicutis and broad, golden yellow to orangish yellow hypocutis"; tissue "mounted in MelzerΓÇÖs reagent turning very dark brown due to the formation of black globules in the hyphae"; clamp connections present, (Cripps), spores 10-11.5 x 5.5-6.5 microns in subspecies argutus, (Brandrud), spores 10-14 x 6-8 microns in subspecies argutus, (Hansen, L.(2))
Habitat / Range
scattered to gregarious or more commonly cespitose [tufted] in Populus tremuloides (aspen) stands with tall grasses, "in mixed stands of aspen and conifers (pine, Douglas fir, true fir, and (or) spruce) and sometimes with admixture of birch or shrubs (rose, hawthorn, willow, alder, spirea)", also reported once with Salix (willow); in Europe with Populus tremula "often on clay soil", (Cripps), a common late fall associate of Quercus garryana (Oregon White Oak), (M. Beug, pers. comm.)
Similar Species
Cortinarius albofragrans is another common large white Cortinarius in woods that feature Quercus garryana - it is distinguished by its somewhat anise-like fragrance and the lack of obscure bands low on the stem that fluoresce pastel orange under Ultraviolet Light (M. Beug, pers. comm.). Cortinarius hedyaromaticus C. Cripps & O.K. Mill. is similar to C. argutus and also favors aspen: "Cortinarius hedyaromaticus is also pale with a slightly rooting stipe base, but it has a strong sweet odor and the stipe apex is not consistently bluish in exsiccate examined, although it has dark globules in MelzerΓÇÖs (see Brandrud 1996b for more details on color reactions).", (Cripps(6) comparing to C. argutus). C. hedyaromaticus was described from Montana and has been confirmed by molecular methods from Colorado, Alaska, Finland, France, Norway, and Sweden (Cripps). Cortinarius talus is pale when young but 1) typically it has a strong, sweet odor, 2) the stem base is bulbous, not rooting, 3) "exsiccate are rusty reddish without bluish or grayish tones", 4) spores are smaller, and 5) the gill trama hyphae lack dark globules in MelzerΓÇÖs reagent, (Cripps).
