E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Features include 1) a large cup that becomes expanded and undulating, with the upper surface light yellowish brown to chestnut brown, 2) thin fragile flesh, 3) exterior lighter in color and almost smooth, 4) growth on ground in woods, and 5) microscopic characters including spores with fine punctate ornamentation.

Peziza arvernensis is found at least in OR, ID, AB, and UT, (Larsen). P. sylvestris (Boud.) Sacc. & Trott found at least in BC, WA, OR, ID, CA, UT, and WY, (Larsen), Switzerland (Breitenbach), United Kingdom (Dennis), Denmark, Finland, and Sweden, (Hansen), and OR, CA, Denmark, and the Netherlands, (Hansen, K.).

Upper surface:
3-10cm, saucer-shaped, bladder-shaped, irregularly undulating; spore-bearing upper surface hazelnut brown to chestnut brown, smooth, (Breitenbach), up to 4cm, cup-shaped then expanded and undulating; upper spore-bearing surface light yellowish brown, (Dennis)

Flesh:
thin, fragile, (Breitenbach), fragile (Dennis)

Underside:
lighter in color than upper surface and becoming paler toward the margin; finely furfuraceous, almost smooth, (Breitenbach), paler; almost smooth, (Dennis)

Stem:
none (Breitenbach)

Microscopic:
spores 14-17 x 8-9 microns, (according to literature 14.5-19 x 8-11 microns), broadly elliptic, finely punctate and rough, colorless, without droplets; asci 8-spored, 180-240 x 11-13 microns, positive reaction with iodine; paraphyses cylindric, septate, tips with slight clavate widening to 5-7 microns, (Breitenbach), 17-19 x 9-10 microns, elliptic, with fine punctate ornamentation, without droplets; paraphyses straight, round at the tip, guttulate [with droplet(s)], (Dennis), spores 15-20 x 9-10 microns, lacking large oil droplets, (Trudell)