pdvmushroom's Identifications

Large, imbricate-pileate polypores growing on cottonwoods (Populus )
Flesh thick, tough-punky, cap surface slightly fibrillose to smooth.
Flesh 2.5 cm deep, tube layer 5 mm deep.
Pore mouths small, subtly angular (not perfectly round), 3-4/mm.
Fresh specimens juicy, with strong almond extract/marzipan/maraschino odor when cut.
Pores turning yellow-orange when dried.

Microscopy:
Hyphae mostly of one type, simple, unseptate, with thick walls. No clamps observed. No cystidia observed. Spores smooth, ellispoid to long-ellipsoid, 7 x 3 microns or longer. Inamyloid.

At first I thought they might be Osteina due to general appearance, but not growing on conifer, not drying bone-hard, and with different micro characters.

Comments from polypore expert Otto Miettinen:

"the fruitbody
structure, spore shape and hyphal structure point towards Polyporus (in the wide, traditional sense). The hyphae look like skeleto-binding
hyphae typical of Polyporus and the core polyporoid clade / polyporaceae
in the modern sense."