Summary:
Lentinellus flabelliformis is recognized by 1) small size, 2) clustered and gregarious habit on hardwood, 3) fan shape with absent or sometimes a short lateral stem (or merely an off-center stem and a more mushroom-like cap), and 4) saw-toothed gills. Other features include 5) a hygrophanous, fawn to vinaceous to buffy ochraceous or grayish brown cap, 6) decurrent close gills that are clay to vinaceous buff, 7) a slightly farinaceous-peppery-bitter taste, 8) a white spore deposit, 9) spiny amyloid spores, and 10) clamp connections. Breitenbach(3) say that they understand Lentinellus omphalodes (Fr.) Karst. to include Lentinellus tridentinus (Sacc. & Syd.) Singer, L. bisus Quel., and L. flabelliformis (Bolt.: Fr.) Ito. Lentinellus micheneri (Berk. & Curt.) Pegler is the preferred name for L. omphalodes Fr.

Cap:
0.5-3cm, fan-shaped, convex becoming flat-convex with margin often incurved, expanding when old and margin slightly crenate [scalloped]; "fawn to vinaceous to clay buff and finally fading to ivory in places"; smooth, (Watling), (0.3)0.5-3.5cm, petaloid to fan-shaped, convex becoming flat, margin somewhat downcurved, expanding fully when old and often slightly crenate, at times somewhat depressed when old near point of attachment; "vinaceous-buff", "pinkish buff", to "tilleul buff", fading to whitish, and at the edge in some, brown, "snuff brown", (Miller), 1.2-3.5cm broad, extremely polymorphic, omphalioid (centrally stemmed), eccentrically to laterally stemmed, phaeomarasmioid [like Phaeomarasmius], to laterally short-stemmed to occasionally laterally sessile (crepidotoid), cap depressed to infundibuliform [funnel-shaped], more or less circular, rounded-petaloid, broadly cuneate, flabelliform [fan-shaped], more or less dimidiate [more semicircular than circular] or broadly reniform [kidney-shaped], margin inrolled to descending, entire, thin; hygrophanous, when fresh watery alutaceous to brownish cinnamon, buffy ochraceous to grayish avellaneous, sometimes with dark brown to "orange cinnamon" poorly defined patches and radial streaks, outward "tilleul buff" to "cinnamon buff", drying tan to sand color, margin yellowish gray when fresh, dark brown when dry; smooth, nearly bald to suede-like, minutely laccate [appearing varnished] when dry "and then sometimes concentrically wrinkled, or minutely micaceous (35X), usually delicately radially streaked dark brown inward and there occasionally splitting", margin striate less than 0.1cm, (Petersen)

Flesh:
thin; colored as cap, (Watling), pliant and more or less tough; whitish, sometimes dark brown, (Petersen)

Gills:
decurrent on stem or radiating from a central point, close to subdistant; clay to vinaceous buff; edges broadly dentate, (Watling), decurrent when stem present, radiating from point of attachment, close to subdistant, 2-3 tiers of subgills, gills broad (up to 0.5cm); nearly colored as cap, "pale pinkish cinnamon" to "pale pinkish buff"; edges "serrate to deeply serrate or dentate", (Miller), subdecurrent to decurrent, extending as lines down stem, subdistant, in at least three ranks, up to 0.35cm broad; whitish to pallid brownish to sand color when fresh, fleshy brown, dull ochraceous brown to "light ochraceous buff" or "cream buff" when dry; "entire when young, to digitate-serrate by maturity", (Petersen)

Stem:
usually absent or if present short, less than 1.5cm, eccentric to lateral; colored as cap or paler; striate from gills, woolly mycelium at base, (Watling), usually absent, if present very short (up to 1.8cm long), off-center to lateral, fluted by decurrent gill edges, "light buff" to "pinkish buff", surrounded at base by cottony mat of fluffy vinaceous to pallid mycelium, (Miller), 0.1-0.9(2.8)cm x 0.15-0.6cm, equal to obclavate, terete [round in cross-section] to longitudinally lined to grooved, tough; dark brown to brown-black, or more or less colored as cap or tinted "Rood''s brown", dark brown to deep purplish brown; base sometimes with delicate grayish brown tomentum and/or delicate rhizomorphs, rhizomorphs flattened, less than 0.1cm wide, webbed at branch points, avellaneous tan to grayish brown; stem smooth to subglabrous [nearly bald], (Petersen)

Odor:
none (Watling), none or slightly aromatic (Miller), weak, sometimes fruity, typical of Lentinellus [usually described as aromatic or peppery-aromatic], (Petersen)

Taste:
slightly mealy-peppery (Watling), subfarinose [somewhat farinaceous] to slightly peppery, (Miller), "weak, more or less bitter and weakly anesthetic when fresh", sometimes slowly weakly acrid [peppery], (Petersen)

Microscopic spores:
spores 4.5-5.5(6.5) x 4-5 microns, nearly round to short-elliptic, minutely punctate (echinulate), amyloid; basidia 4-spored, 25-30 x 5-7.5 microns, "fusiform to narrowly clavate often with attenuated tip, thin-walled", colorless; pleurocystidia similar to cheilocystidia [which are however not described by Watling]; clamp connections present, (Watling), |spores 5-6.5(7) x 4-5(6), nearly round to short-elliptic, minutely echinulate [finely spiny], light yellowish in KOH, walls and spines amyloid (deep blue); basidia 4-spored, 22-32 x 5-7.5 microns, clavate, thin-walled, colorless; pleurocystidia and cheilocystidia (25)30-42(55) x (4)5-7 microns, protruding 1/3-1/2 of total length, "fusiform often with narrowly attenuated apex", colorless, thin-walled, scattered or occasionally numerous on gill edge; cuticle of erect densely packed hyphae 2.5-8 microns wide, with protruding to embedded pileocystidia 30-148 x (2.5)4.2-8.0 microns, incrusted if embedded, and dingy yellow-brown in KOH or Melzer''s reagent, (Miller), |spores 4.5-7.0 x 3.4-5.0 microns, elliptic to broadly ovate, usually adaxially flattened, ornamentation of scattered verruculae sometimes distinctly visible at 1500x, spores weakly to moderately amyloid, colorless, thin-walled (up to 0.5 microns), one to several droplets, hilar appendix small, obscure; basidia 4-spored, 18-30 x 4.0-6.0 microns, emergent up to 12 microns, "clavate to plump cigar-shaped when mature", finely multigranular, with clamp connections, hymenium composed of up to 3 other elements: 1) pleurocystidia emergent up to 20 microns, 26-34 x 5.0-13 microns, "fusiform with lanceolate to bluntly lanceolate apex", colorless, thick-walled in lower part (wall up to 0.7 microns thick), thin-walled at top, "contents homogeneous to gloeoplerous in median inflated area", 2) gloeocystidia emergent up to 20 microns, 3.5-8.0 microns wide, arising in hymenium or from lateral stratum, bluntly to narrowly clavate, yellow-refringent in KOH, contents coscinoidal [foamy] or with acicular inclusions, and 3) leptocystidia emergent up to 25 microns, 2.5-4.5 microns wide, filamentous, gloeoplerous; cap cuticle 15-20 microns thick, "a repent, coherent, radial layer of generative hyphae involved in mucus", hyphae 2.0-7.5 microns wide, thin-walled to thick-walled (up to 0.7 microns thick), "with occasional to common erect short branches", colorless, watery tan in mass, with clamp connections, suprapellis not developed; cap trama loosely to tightly interwoven, dimitic, 1) generative hyphae 2.0-7.0(30.0) microns wide, thin-walled to thick-walled (commonly up to 1.2 microns thick, rarely to commonly blocking cell lumen), tortuous, often branched, commonly inflated to vermiform, "clavate, strangulate, or fusiform shapes (and there usually thick-walled)", inamyloid to weakly amyloid (pale gray) over thick-walled segments, colorless, with clamp connections, 2) gloeoplerous hyphae 2.0-7.0 microns wide, occasional, [but abundant in subpellis (2.0-6.5 microns wide, coarsely coscinoidal) and gill trama (2.0-4.5(6.5) microns wide, hardly coscinoidal to coscinoidal)] refringent in KOH, pale straw-colored in KOH, thin-walled, contents finely coscinoidal to resinous with acicular crystals, (Petersen)

Spore deposit:
white (Watling, Miller)

Notes:
Lentinellus flabelliformis material was examined from WA, OR, ID, AZ, CO, ME, MD, MI, NH, Sweden, and Switzerland, (Miller(10)). Collections were examined from OR, NS, MI, NY, Mexico, Ecuador, Austria, Finland, France, Italy, Macedonia, Sweden, Switzerland, and the United Kingdom, (Petersen(25)). There are collections from BC at the University of British Columbia.

EDIBILITY

Synonyms and Alternate Names:
Claudopus subargillaceus Kauffman