Details about map content are available here Click on the map dots to view record details.
Species Information
Summary: Armillaria nabsnona is a member of the Armillaria mellea group, designated North American Biological Species IX. Distinguishing features from other Armillarias are a more orange coloration when fresh, lack of scales on the cap (but small black hairs may be found as in A. mellea), a narrower stem in comparison to the size of the cap, a darker stem, especially when dried, and hardwood habitat especially red alder. Microscopically the pattern of branching of the basidia is distinctive. It is the only Armillaria known to fruit in spring in the Pacific Northwest (although commoner in fall). The information here is derived from Volk(1) unless otherwise stated.
It is found at least in BC, WA, OR, ID, AK, and CA, (Volk), and Japan, (Baumgartner).
Cap: 4-7cm across, convex becoming flat, margin incurved slightly; hygrophanous, "snuff-brown" on disc, paler toward margin, often with darker bruise-like areas on or near surface; appears slimy when wet, smooth, no scales but sometimes with short dark fibrils (hairs) on disc when young, translucent-striate to furrowed, (Volk(1)), orange-brown (Volk(2))
Flesh: 0.05-0.1cm thick; white, in stem white
Gills: adnate to subdecurrent [somewhat decurrent], subdistant, 0.075-0.1cm wide; white to cream-colored, darkening to pinkish tan, often developing brownish patches
Stem: 8-10cm x 0.2-0.3cm, widening to 0.4-0.5cm at base, fibrous, peeling away in parallel strips as is typical for Armillaria species; "mummy brown" [blackish brown] at base, paler "buckthorn brown" to "warm buff" near ring, white cottony patches below ring, rhizomorphs frequently lacking but when present thick (0.1-0.2cm), black and branching
Veil: partial veil "dense white cottony until rupture", ring flares up at first, soon becomes ragged, sometimes persisting as evanescent cortina
Microscopic spores: spores (6)8-10 x 5.5-6.5 microns, smooth, inamyloid, colorless, somewhat thick-walled when mature; basidia 4-spored, 25-35 x 5.5-6 microns, clavate, has a distinctive pattern of branching in the development of the basidia, virtually all basidia basally clamped, second basidium emerges from clamp of first, the third from the second and so on, particularly obvious in immature specimens; pleurocystidia and cheilocystidia not observed, but thin (2-3 microns) wide hyphae-like cells can sometimes be found among basidia; clamp connections on basidia, in some hyphae in subhymenium, occasional in gill trama, but septa simple in stem cuticle, stem context, and partial veil
Spore deposit: white
Habitat / Range
primarily on hardwoods in riparian areas, especially Alnus (alder), in gregarious clusters but not cespitose, spring and fall, (Volk(1)), on hardwood, especially Alnus rubra (Red Alder), (Volk(2))
Similar Species
Armillaria mellea is similar, but A. nabsnona is not cespitose, has unbranched terminal cells in the cap cuticle, and has clamps at the base of the basidia. (A. mellea has frequently branching terminal cells in the cap cuticle and lacks clamps at the bases of basidia.). See also SIMILAR section of Armillaria ostoyae.
