Summary:
This is a member of the Phellinus igniarius complex according to Zhou, L.-W.(1). Features include 1) a bracket-like fruitbody on living aspen, attached to branch scars by a granular core of tissue, 2) the upper surface (at about 45 degrees) pale brown tomentose, becoming black, crusted and cracked, 3) the pore surface at about 45 degrees and purplish brown with small circular pores, 4) tubes that are stuffed with white mycelium, and 5) microscopic characters.

Odor:
sweet wintergreen, (Gilbertson), similar to methyl salicylate (Breitenbach from Romagnesi), indistinct (Buczacki)

Taste:
indistinct (Buczacki)

Microscopic:
spores 4.5-5 x 4-4.5 microns, nearly round, smooth, inamyloid, colorless, "with thickened wall at maturity"; basidia 4-spored, 8-10 x 6-7 microns, broadly ovoid, simple-septate at base; setae few to numerous, 12-30 x 6-7.5 microns, projecting to 15 microns, ventricose to subulate [awl-shaped], brown in KOH, thick-walled; hyphae of context of 2 types: 1) 2-3 microns wide, pale yellowish to almost colorless, thin-walled, simple-septate, 2) 4-6 microns, dark reddish brown, thick-walled; granular core "composed of densely interwoven, branching hyphae with clusters of thick-walled, dark reddish brown, irregularly shaped and contorted cells"; hyphae of trama with parallel arrangement, (Gilbertson), spores 4.8-5.6 x 3.5-5 microns, nearly round, smooth, inamyloid, colorless, thick-walled; setae common, 16-25 x 7-9 microns, brown, thick-walled, (Breitenbach)

Spore Deposit:
white (Buczacki)

Notes:
Phellinus tremulae has been found in BC, WA, OR, ID, AB, MB, NT, NB, NF, NS, ON, PQ, SK, YT, AK, AZ, CA, CO, CT, IA, IL, IN, MA, MD, ME, MI, MN, MT, ND, NH, NM, NV, NY, OH, PA, SD, UT, VA, VT, WI, WV, and WY, (Gilbertson). It also occurs in Europe (Breitenbach).

Synonyms and Alternate Names:
Corticium pini-canadensis (Schwein.) D.P. Rogers & H.S. Jacks.
Fomes igniarius orma tremulae Bondartsev
Radulum pini-canadensis Schwein.