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Species Information
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.
Peziza petersii is found at least in BC, WA, and OR, (Larsen), and NY to WI and WY, (Seaver).
Upper surface: up to 5cm, cup-shaped; spore-bearing upper surface brown with grayish tints, (Dennis), 2-5cm across, deeply cup-shaped, upper surface grayish brown with blue tinge, (Hansen), reaching 3-5cm across, at first closed and spherical, gradually expanding, regular or much contorted; upper surface pale brown to dark brown; margin usually crenate [scalloped], (Seaver)
Flesh: thin; gray, (Dennis)
Underside: lead-gray in lower part, becoming brownish toward margin; scurfy, (Dennis), "outer surface above glabrous, bluish", (Hansen), whitish, becoming dingy when old; densely pustulate, the pustules giving rise to bran-like particles as the fruitbody matures, (Seaver)
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)
Habitat / Range
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)
