Summary:
Features include 1) resupinate growth on wood, 2) thin, soft, waxy patches that are whitish, and smooth to slightly bumpy, 3) spores that are narrowly elliptic or suballantoid, smooth, inamyloid, and colorless, with numerous oil droplets or with grainy oil contents, 4) cystidial organs of three types: a) cystidia that are generally more or less capitate but sometimes cylindric, apically rounded, projecting, usually naked but when intact apically encrusted with crystals or covered with amorphous matter, b) gloeocystidia that are enclosed, mostly fusiform, always tapering to the apex, with yellowish, homogeneous contents, and c) stephanocysts that are about 10-12 microns wide, with rounded dense homogeneous protoplasm, surrounded by a whorl of small teeth, and 5) a monomitic hyphal system, usually with clamp connections. Eriksson & Strid say that H. praetermissum in the sense they describe is a complex rather than a single species, (Eriksson(3)).

Microscopic:
SPORES 8-10 x 3.5-4.5 microns, "cylindric-oval, some flattened or concave on one side, smooth", inamyloid, colorless, with droplets or granular contents; BASIDIA 4-spored, 25-28 x 6.5-7.5 microns, clavate, with basal clamp connection; CYSTIDIA of 3 types: 1) exserted [projecting] cystidia 30-70 x 7-9 microns, cylindric to somewhat capitate, some encrusted at the tips, or according to the literature surrounded by amorphous material, 2) cystidia imbedded in hymenium, 60-90 x 8-14, +/- fusiform, sulfo-negative, and 3) stephanocysts enclosed in hymenium, pyriform [pear-shaped], "some with toothed equatorial zone" that is difficult to see; HYPHAE monomitic up to 7 microns wide, septa usually with clamp connections, (Breitenbach), SPORES 8-11 x 4-5 microns, narrowly elliptic or suballantoid, "adaxial side often but not always somewhat concave", inamyloid, thin-walled, with numerous oil droplets or with grainy oil contents; BASIDIA 22-28 x 6-7 microns, "subclavate, sometimes constricted or slightly sinuous", "with normally 4 sterigmata and with basal clamp"; CYSTIDIAL ORGANS of three types: 1) cystidia generally more or less capitate but sometimes cylindric, apically rounded, 10-90 x 6-10 microns, the apical head 4-10 microns wide, neck 3-5 microns wide, these cystidia "projecting and always present but varying in number, sometimes few or rare", "in the slides as a rule naked but when intact apically encrusted with crystals or covered with excreted, amorphous matter", 2) gloeocystidia, 50-100 x 8-12 microns, enclosed, always frequent, mostly fusiform, always tapering to the apex, thin-walled, with yellowish, homogeneous contents, and 3) stephanocysts about 10-12 microns wide, "rounded bladders with dense homogeneous protoplasm, surrounded by a whorl of small teeth", "very variable in number", in some slides not found at all, in others numerous and easily found; HYPHAE monomitic about 3-4 microns, thin-walled, "forming a very dense context in the subhymenial part, as a rule looser next to the substrate but with great variation", (Eriksson)

Notes:
Peniophorella praetermissa has been found in BC, WA, OR, ID, AB, MB, NB, NS, ON, PQ, AZ, CO, CT, DC, FL, IA, IL, LA, MA, MD, MI, MN, MS, MT, NC, NH, NJ, NM, NY, TX, VA, and WI, (Ginns). It has also been found in Europe including Switzerland (Breitenbach) and Scandinavia (Eriksson).

Synonyms and Alternate Names:
Phacorrhiza sclerotioides Pers.
Typhula friesii P. Karst.