Summary:
Cystoderma amianthinum group is recognized by its ochre color, granulose cap and stem, fragile veil that may leave slight ring on stem, and amyloid spores. |Breheret(1) suggest that the compound responsible for the "musty-earthy" or "green-corn" odor is geosmin, a sesquiterpenoid compound. |C. amianthinum is common in the Pacific Northwest (Ammirati(1)). There are more than one species covered by the name Cystoderma amianthinum in the Pacific Northwest, and Saar suggested at least two species in Europe, (D. Miller, pers. comm.) |Smith(46) examined collections of a number of varieties and forms, 1) var. typicum with spores 4.5-6.5(7.5) microns and gill trama colorless in KOH, with four forms - forma typicum, with cap yellow to tawny at first, forma olivaceum with cap olive when young (not Pacific Northwest), forma alba with cap whitish (not documented from PNW), and forma rugosoreticulatum with cap surface conspicuously rugose-reticulate [wrinkled-netted], 2) var. sublongisporum with spores (5.3)6.2-7.5(8) x 2.8-3.8 microns, gill trama pale cinnamon in KOH at least in some sections, and 3) var. longisporum with spores 7-9 x 4-4.7 microns (not documented from Pacific Northwest), (Smith(46)). |Cystoderma amianthinum has been confirmed as a host of Squamanita pearsonii and Squamanita paradoxa (Griffith(1)).

Cap:
2-5cm across, bell-shaped or somewhat conic becoming convex or umbonate to nearly flat; tawny-ocher to ocher-brown, ocher-buff, or yellowish, a white form also occurs; dry, prominently wrinkled radially in one variety [forma rugosoreticulatum], covered with mealy or powdery granules that may wear off, "margin often hung with veil remnants", (Arora), (1.5)2-3.5(4.5)cm across, "obtuse to convex, expanding to broadly convex or at times obtusely umbonate", margin appendiculate "with somewhat triangular flaps of broken veil tissue"; dull yellowish brown ("buckthorn brown") on disc and pale yellow ("antimony yellow") toward margin or pale yellow overall, finally tawny ("tawny" to "ochraceous tawny") over disc and paler toward margin, when wet sometimes rich dark brown ("auburn"); dry, granulose, the granules often aggregated into spot-like scales, (Smith(15)), very variable in color, can be pale yellow, ocher-yellow, orange-yellow, to olive-yellow, or even rust-red, (Breitenbach)

Flesh:
thin (Arora), thin except in disc; white or whitish; in stem, pith is pallid, (Smith(15))

Gills:
"adnexed to adnate, crowded"; "white or creamy or tinged yellow-orange", (Arora), "squarely adnate or ascending at first, but often developing a tooth and becoming somewhat sinuate", close to crowded, 2 tiers of subgills, moderately broad (0.25-0.35cm); white or whitish at first but usually pale yellowish when mature, sometimes distinctly yellowish ("warm buff"); edges even, (Smith(15))

Stem:
2.5-7cm x 0.3-0.8cm, equal or slightly enlarged in lower part; whitish above the veil, cap-colored in lower part; smooth above the veil, sheathed with granules or granulose scales in lower part, (Arora), 3-6cm x 0.3-0.7cm at top, equal or widening very slightly downward, solid but often becoming hollow; cap colored up to ring that is rarely well formed, pallid to yellowish above ring; sheathed with granulose covering up to ring, pruinose above ring, base with adherent white mycelium, (Smith(15))

Veil:
fragile, ring slight on stem or often disappearing, (Arora), median to superior ring rarely well formed, when present tawny and granulose on underside, pallid on upper side, (Smith(15))

Odor:
mild or strongly pungent, (Arora), not distinctive (Smith(15)), disagreeable, mawkish or not distinctive, (Smith(46)), in var. rugosoreticulatum pungent, (Lincoff(2)), often like freshly husked green corn (Ammirati)

Taste:
not distinctive (Smith(15))

Microscopic spores:
spores 4-7 x 3-4 microns, elliptic, smooth, amyloid, (Arora), spores 5.5-6.5 x 3-3.5 microns, narrowly elliptic, smooth, amyloid; basidia 4-spored, 24-28 x 6-7 microns, clavate; pleurocystidia not seen, cheilocystidia absent to very rare, 26-34 x 5-7 microns, narrowly ventricose with obtuse tips; cap trama with a differentiated surface covering of chains of inflated ellipsoid to spherical, smooth, brown-walled cells (revived in KOH) 18-32 x 10-24 microns, the chains readily breaking up; clamp connections present on stem hyphae, (Smith(15)), spores (4.2)4.5-6.5(7.5) x (2)2.8-3.5 microns, narrowly elliptic, distinctly though not always strongly amyloid; basidia 4-spored, 21-28 x 5.5-7 microns, clavate; pleurocystidia not seen, cheilocystidia absent or when present very rare, 26-34 x 5-7 microns, narrowly ventricose with obtuse apices; cap cuticle of chains of spherical to ellipsoid cells 18-48(60) x 10-24(40) microns, "their walls smooth to very faintly rugulose and rusty cinnamon when revived in KOH, the chains readily breaking up into the component cells, very few narrowly ellipsoid to subcylindric cells"; cap trama of colorless, inamyloid, loosely interwoven hyphae, the subcuticular filamentous hyphae colorless to only slightly pigmented; clamp connections present, (Smith(46)), spores amyloid, but sometimes very weakly amyloid, (Breitenbach)

Spore deposit:
white (Arora)

Notes:
It is found at least in BC (Redhead(5)), and WA and OR (Smith(46)), and it is reported from ID by Andrew Parker, pers. comm. Smith says it is "not infrequently collected in our northern and western states". Lincoff says it is found "throughout North America". Miller(9) documents it for AK. It is also found in Europe. Smith(46) examined collections of var. typicum forma typicum from WA, OR, also ON, QC, CA, MA, ME, MI, NC, NH, NY, TN, France, and Russia, of var. typicum forma olivaceum from Siberia in Russia, of var. typicum forma album from ME, of var. typicum forma rugosoreticulatum from WA, OR, CA, MI, and TN, of var. sublongisporum from WA, OR, ON, ME, NY, (and found in TN), of var. longisporum none, but described from France.

EDIBILITY

may be edible but not recommended because easy to confuse with poisonous species, e.g. Lepiota castanea, (Arora)