Summary:
Features include minute, whitish cups that are pruinose on the disc and downy on the exterior, growth on pyrenomycetes, and microscopic characters including branching paraphyses.

Microscopic:
spores (13.9)14.6-20.5(22.0) x 3.7-5.1 microns, "often slightly curved, shorter at the ascus apex, longer toward base of ascus", aseptate at first, soon 3-septate (evident in KOH-phloxine-glycerine or lactic acid - cotton blue, but many authors have failed to see septa); asci (78)80-110 x (8.0)8.8-10.2(11.0) microns, with pore blue in Melzer''s reagent; paraphyses filiform but apically deformed and propoloid, (Korf), spores 15-21 x 4-4.5 microns, elliptic-fusiform, sometimes slightly bent, smooth, colorless, usually with 4 droplets, biseriate, sometimes with indistinct septum; asci 8-spored, 105-120 x 11 microns, positive reaction in iodine; paraphyses filiform, cylindric, and strongly forked at tips, (Breitenbach)

Notes:
Polydesmia pruinosa is found in BC, WA, and also NY, PA, TN, Canary Islands, and Madeira; it is common and widespread in the United Kingdom and Europe on many different pyrenomycetes; it can be common in the Pacific Northwest, but is rarely collected, (Korf).

Synonyms and Alternate Names:
Chaetoporellus latitans (Bourdot & Galzin) Bondartsev & Singer