Summary:
Section Obtusi (used to be in Subgenus Telamonia but not closely related). Cortinarius acutus is a small, slender, hygrophanous, light red-brown to yellow-brown species that belongs to the Cortinarius obtusus complex, and is reminiscent of a Galerina. C. acutus is characterized by a pointed cap with a colorless umbo, very distinctly serrulate gill edge due to large inflated sterile cells, and relatively pale colors of the fruit bodies, (Brandrud). It is a member of the Cortinarius obtusus group described by Stuntz which also includes Cortinarius impolitus, C. scandens, C. fasciatus, and C. pulcher: Cortinarius acutus is distinguished by a prominent sharp umbo, translucent-striate cap, and slender pallid satiny stem, (Stuntz(5)). Cortinarius acutovelatus could be added to the group although there is still some lack of clarity about the relationship between C. acutovelatus and C. acutus.

Cap:
0.3-1.5cm across, conic to bell-shaped, then convex, "usually with an acute and hyaline umbo"; hygrophanous, light red-brown to ochraceous yellowish brown, drying up radially, yellowish white when dry; fibrillose from veil when young, margin strongly translucent-striate, (Brandrud), 0.5-2.5cm across, conic or conic - bell-shaped with an acute umbo; hygrophanous, watery-rufous-cinnamon when moist, pale alutaceous when dry; minutely silky, striate to the umbo, margin white-cortinate, becoming bald, (Kauffman), 0.6-2.6cm across, conic at first, expanding with a prominent sharp umbo; cinnamon-brown to tawny brown when moist, fading to pallid; bald, appearing silky when dry, translucent-striate, (Stuntz)

Flesh:
submembranaceous [somewhat membranaceous]; yellowish, (Kauffman), very thin (Stuntz)

Gills:
moderately crowded to distant; yellowish brown; edge white and serrate, (Brandrud), "adnate, seceding, close or scarcely subdistant, thin, not broad"; pale ochraceous at first, then ochraceous cinnamon; the edge entire, (Kauffman), pale brownish or pallid when young (Stuntz)

Stem:
1.5-5cm x 0.1-0.3cm, equal, slightly pointed at base, often curved; white, soon pale yellowish brown, (Brandrud), 4-8cm x 0.1-0.2cm, equal, slender, flexuous [wavy], tubular; yellowish at first, becoming paler; silky from evanescent white cortina, becoming bald, (Kauffman), 2.6-5.1cm x 0.3-0.5cm, equal, hollow, fragile; "white or pallid, becoming dull brown toward the base in older specimens"; bald and satiny, sometimes with slight evanescent cortinal zone, lower part of stem without any zones or patches of universal veil, (Stuntz)

Veil:
white, sparse, floccose or fibrillose universal veil, (Brandrud), sometimes with slight evanescent cortinal zone, lower stem without any patches of zones of universal veil, (Stuntz)

Odor:
weak, iodoform-like, more distinct on drying, (Brandrud), radish when crushed, (Stuntz), iodine (Miller)

Taste:
radish (Stuntz), mild (Miller)

Microscopic spores:
spores 7-8 x 4-5 microns, elliptic to broadly elliptic, finely and densely verrucose; gill edge distinctly sterile with numerous balloon-shaped sterile cells, (Brandrud), spores 7-9.5 x 5-5.5 microns, elliptic, smooth, (Kauffman), spores 7.5-10.7 x 4.5-6 microns; basidia (2)4-spored, 23-30 x 8-9.5 microns, with basal clamp connection; no pleurocystidia, cheilocystidia "polymorphic, abundant and clustered, clavate, vesicular, or fusiform", end cells, 20-55 x 10-27 microns, (Breitenbach), [presumably without apical pore]

Spore deposit:
rusty brown (Miller)

Notes:
Cortinarius acutus was recorded by Smith in 1941 from WA and in 1937 from CA, and is common in WA according to Stuntz in Stuntz(5). There are collections labeled C. acutus from BC at the Pacific Forestry Centre and the University of British Columbia. There are collections labeled C. acutus from WA, OR, CA, and Austria at the University of Washington.

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