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Species Information
Summary: Armillaria sinapina is a member of the Armillaria mellea group. It is differentiated from the other members of group by a general brownish color with reddish tinges, a thin delicate ring (annulus), growth on conifers and hardwoods, cylindric rhizomorphs, and clamp connections on basidia as well as binucleate subhymenial cells. The description is derived from Berube except where noted. According to Volk(2), accessed February 9, 2015, the golden yellow color of the universal veil has not been observed on western specimens, but in fact golden yellow veiled Armillaria collections are found in BC, WA, and AB (Jim Ginns, Andrew Parker, Martin Osis, pers. comm.).
It is found at least in BC from 49 to 57 degrees North (widespread and common), (Allen), WA, ID, AK, (Volk(2)), and QC and NY (Berube).
Cap: 2-6cm across, conic - bell-shaped to bell-shaped, convex then flat-convex, occasionally mammillate, margin straight; sometimes hygrophanous, grayish orange or 'cinnamon', sometimes with very dark shades of 'Venetian red', 'eye brown' or 'chestnut'; dry, fibrillose, rarely bald, usually covered with dark brown or 'tile red' tufts of hairs and fibrils or sometimes densely covered with small scales, universal veil 'golden yellow' to 'mustard yellow', leaving small tufts of fibrils, sometimes wart-like, less frequent at center of mature fruiting bodies, margin sometimes with striations, with membranous white patches, remnants of partial veil still adhering to cap
Flesh: thin to thick, firm; white to cream
Gills: sinuate, subdecurrent to sometimes strongly decurrent, thick, close; ''cream'' to ''cinnamon'' when old
Stem: 4-8cm x 0.5-1cm, club-shaped, fibrous, ring (annulus) fibrous; covered with fine fibers, grayish brown to ''brick red'', occasionally bruising ''photo brown'', darker at the base, zoned with ''golden yellow'' ringlets of universal veil, sometimes reduced to faint yellow fibers; slightly striate
Veil: universal veil ''golden yellow'' to ''mustard yellow'', covering entirely the primordia and immature fruiting bodies, leaving small tufts of fibrils on cap, sometimes wart-like, less frequent at center of mature fruiting bodies; partial veil leaves remnants still adhering to cap; ring (annulus) "fibrous, sometimes membranous but very thin and delicate", later collapsing and usually appressed to stem, white to ''cream'' on upper part, ''golden yellow'' to ''mustard yellow'' on lower part, sometimes totally ''golden yellow'' or ''mustard yellow''
Microscopic spores: spores 8.2-10 x 5.9-8 microns, broadly elliptic to ovate, smooth, inamyloid, apiculate; basidia 4-spored, club-shaped, some with clamp connections at base; pleurocystidia absent; subhymenial hyphae filamentous, binucleate, without clamp connections
Spore deposit: ivory
Habitat / Range
singly or in small fasciculate (bundled) groups or two to five on dead stumps and healthy roots, and trees, (hardwood and conifer), (Berube), singly, or sometimes in clusters of two or three; in northeastern North America found mainly on hardwoods and occasionally conifers, but in the Pacific Northwest more common on conifers, (Volk)
Similar Species
Armillaria ostoyae, A. mellea, and A. gallica are similar, but Armillaria sinapina "can be differentiated by its general brownish color often with tile red tinges but more specifically by its golden yellow universal veil that entirely covers immature fruiting bodies and later leaves remnants consisting of yellow warts or lumps of tissue on the cap, a yellow annulus, and many patches and fibers on the stipe"; in addition, rhizomorphs are cylindrical in A. sinapina (belt-shaped in A. ostoyae), (Berube). It is difficult to distinguish between A. ostoyae and A. sinapina in a colonized stump because both produce white mycelial fans in the bark and cambial zone; however, A. sinapina produces an extensive network of monopodially-branched rhizomorphs while A. ostoyae produces small amounts of dichotomously branched ones; also the fruiting bodies of A. sinapina are usually darker in color, with darker cap scales, smaller, and more numerous than those of A. ostoyae, (Allen). Armillaria mellea sensu stricto is similar but A. sinapina has a nonviscid, predominantly brownish cap with numerous small scales or fibrils, and clamp connections on basidia, as well as binucleate subhymenial cells, (Berube). Armillaria gallica has no cells in the annulus greater than 8 microns, in contrast to A. sinapina which has some, (Volk).
