E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
The distinctive feature is the bright yellow-orange rhizomorphs which are seen in the litter or humus layers of acid coniferous forests, more commonly than the fruitbodies. Other features include 1) resupinate growth on rotten wood or other substrates, 2) soft, cottony fruitbodies that are generally yellow (but sometimes whitish), and smooth to slightly tuberculate (fine-pored under a 50x lens), 3) spores that are nearly round, smooth, rather thick-walled, non-amyloid, and colorless, and have one droplet, and 4) a monomitic hyphal system, the hyphae without clamp connections, the basal and rhizomorph hyphae with yellow encrustation. Corticium bicolor Peck may be a different species but the name has been used for this species in the past. Furthermore the online Species Fungorum, accessed June 10, 2016, gives the current name of Piloderma fallax (Lib.) Stalpers as Piloderma bicolor (Peck) Julich with Corticium bicolor Peck as a synonym. Piloderma fallax is evidently a common species in the whole of the temperate region of the northern hemisphere, (Eriksson). Not all of the yellow rhizomorphs in the acid forest soils belong to this species but that is by far the most frequent species with bright yellow rhizomorphs, (Eriksson).

Piloderma fallax has been found in BC, WA, OR, ID, AB, MB, ON, PQ, SK, AZ, CA, CO, MA, ME, MI, MN, MT, NC, NH, NJ, NM, NY, PA, and WI, (Ginns). It has also been found in Austria, Czechoslovakia, Denmark, Finland, France, Germany, Hungary, Norway, Poland, Sweden, and the USSR, (Julich). It occurs in Switzerland and in Asia, (Breitenbach).

Fruiting body:
resupinate, loosely attached to substrate, forming thin, membranous patches several centimeters across, consistency cottony, soft; ocher-yellow, saffron-yellow, to sulfur-yellow, sometimes also cream or white; "smooth to slightly tuberculate (fine-pored with strong magnification)"; "margin irregularly fringed with fine rhizomorphs", these permeating the substrate, 0.01-0.1cm wide, branched, conspicuously bright yolk-yellow, (Breitenbach), "resupinate, at first thin and soft, then submembranaceous, loosely attached"; initially usually bright yellow, with the thickened part of the spore-bearing surface fading to pale yellow or even almost white; "finely porulose (lens 50 x), smooth to irregularly folded or somewhat tuberculate"; margin not differentiated; rhizomorphs "regularly present, conspicuous, yellow-orange", 0.01-0.1cm thick, more or less branched, (Eriksson), spore deposit white (Buczacki)

Microscopic:
SPORES 3-3.5 x 2.5-3 microns, nearly round, smooth, inamyloid, colorless, rather thick-walled, with one droplet; BASIDIA 4-spored, 12-18 x 3-4.5 microns, narrowly clavate, somewhat constricted, without basal clamp connection; CYSTIDIA not seen; HYPHAE monomitic, without clamp connections; SUBHYMENIAL HYPHAE 2.5-3.5 microns wide, smooth to slightly encrusted; BASAL HYPHAE 3.5-4.5 microns wide, strongly encrusted with fine crystals; RHIZOMORPH HYPHAE 3 microns wide, encrusted with large, elongated crystals that are yellowish in Melzer''s reagent, as well as small crystals, (Breitenbach), SPORES 3-3.5(4.5) x 2-3(3.5) microns, mostly nearly round, sometimes subelliptic, smooth, yellowish in Melzer''s reagent when single, more or less reddish brown in masses, spore with thickened walls, usually with one large oil droplet; BASIDIA 12-20 x 3.5-4.5 microns, "clavate, basal part often narrowed to a hypha-wide part which may be prolonged", without basal clamp connection; normally 4-spored; CYSTIDIA none; HYPHAE monomitic, 2.5-3.5 microns wide, without clamp connections, "with numerous anastomoses, often with attached baculiform crystals"; SUBBASIDIAL HYPHAE thin-walled, richly branched; SUBICULAR HYPHAE with straight, sparsely branched, with thin or slightly thickened walls, covered with small, yellow grains (visible in Melzer''s reagent), single hyphae yellow in Melzer''s reagent but in mass (e.g. in rhizomorphs) reddish brown; RHIZOMORPH HYPHAE "parallel, densely packed, kept together by anastomoses", (Eriksson)