Summary: Features include 1) a cup-shaped fruitbody with a grayish brown upper surface and a scurfy exterior that is gray in lower part becoming brownish toward the margin, 2) growth on burned ground or burned wood, and 3) microscopic characters.
Microscopic: spores 10-12 x 5.5-6 microns, finely warted, with 2 oil droplets; asci about 200 x 10 microns; paraphyses somewhat clavate, up to 7 microns wide at tip, "which contains brown globules and is often curved", (Dennis), spores 11-12 x 6-6.5 microns, narrowly elliptic, with elongate delicate warts (illustration indicates warts in the form of short ridges), with 2 small droplets, (Hansen), spores 15-17 x 8-10 microns, elliptic, becoming minutely warted, colorless to faintly yellowish, uniseriate; asci reaching a length of 275 microns and width of 12-14 microns; paraphyses strongly widened in upper part and reaching width of 7-8 microns at tip, (Seaver)
Notes: Peziza petersii is found at least in BC, WA, and OR, (Larsen), and NY to WI and WY, (Seaver).
Habitat and Range
SIMILAR SPECIES
See also SIMILAR section of Peziza domiciliana.
Habitat
often clustered, on "burnt ground in woods and on charred stumps", June to October, (Dennis), on burnt ground in hardwood forests with rich soil, fall, (Hansen), gregarious, scattered or cespitose on charcoal and burned areas, (Seaver)