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

Summary:
Features include 1) resupinate growth on conifer wood, 2) a soft-cottony to somewhat waxy, easily separable fruitbody that is cream to pale buff, smooth to papillate or strongly hydnaceous, the margin abrupt, floccose, and rhizomorphic, 3) spores that are oval to nearly round, minutely echinulate, amyloid, and colorless, 4) projecting gloeocystidia that are cylindric or with irregular constrictions and swellings, and are not incrusted, and 5) subicular hyphae of 3 types: a) narrow, thick-walled, aseptate, dextrinoid, b) narrow, thick-walled, septa with clamp connections, and non-dextrinoid, and c) wide and with rare clamp connections, non-dextrinoid.

Scytinostromella arachnoidea has been found in BC, WA, OR, ID, AK, AZ, FL, NC, NH, NM, and NY, (Ginns(5)).

Fruiting body:
"annual, soft-cottony, easily separable"; cream to pale buff; "smooth to papillate or strongly hydnaceous"; margin rhizomorphic, (Gilbertson), widely effused, 0.04-0.06cm thick, subceraceous [somewhat waxy]; cream buff; "broken into tufted areolae, exposing the woolly floccose subiculum"; "margin abrupt floccose", (Jackson)

Microscopic:
SPORES 3.5-4.5 x 2.5-3.5 microns, oval to nearly round, minutely echinulate, amyloid, colorless in KOH solution; BASIDIA 14-16 x 5-5.5 microns, clavate, with median constriction; CYSTIDIA hymenial, "as projecting ends of large, thin-walled hyphae", "cylindric or with irregular constrictions and swellings", 6-8 microns wide and projecting up to 70 microns, not encrusted; subicular hyphae of 3 types: 1) 2-2.5 microns wide, thick-walled, aseptate, moderately to strongly dextrinoid, 2) 2-2.5 microns, thin-walled, nodose-septate (septa with clamp connections), not dextrinoid, and 3) 5-8 microns wide, thin-walled, with rare clamp connections, not dextrinoid, (Gilbertson), gloeocystidia cylindric or with irregular constrictions and swellings; hyphae of 2 types: some thick-walled, aseptate, dextrinoid, (Martin), SPORES 3.5-4.5 x 3-3.5 microns, nearly round or broadly elliptic, "slightly depressed on one side with inconspicuous apiculus", minutely asperulate, strongly amyloid, thin-walled; BASIDIA 4-spored, 35-45 x 5-5.5 microns, narrowly clavate, sterigmata upright, subulate; GLOEOCYSTIDIA numerous, 60-120 x 5.5-8 microns, cylindric to clavate, somewhat flexuous [wavy], "contents guttulate becoming pseudoseptate after withdrawal of contents"; an upper layer of more or less upright, thin-walled hyphae with clamp connections gives rise to the gloeocystidia and basidia; subiculum made up in part of densely interwoven basal layer of fibrous, nonseptate hyphae, 1.5-2.5 microns wide, with thick walls, turning brown in Melzer''s reagent, (Jackson), SPORES 3.5-4.5 x 3-3.5 microns, oval, finely asperulate, and strongly amyloid; gloeocystidia, sulfo-reaction unknown; possesses dextrinoid, sparsely branched hyphae, (Boidin)