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Peziza species 01 (brunneoatra)

by Michael Kuo, 3 July 2024

I've collected this cup fungus a few times over the years, and it's pretty distinctive. It appears in spring, in hardwood forests in the Midwest, growing directly from the ground. It's a small to medium-sized cup with a bald upper surface, and its colors are somber, ranging from dark brown to black. Under the microscope, it features ascus tips that turn blue in Melzer's Reagent, slightly swollen paraphyses, and ellipsoid spores with very prominent ornamentation—a series of ridges and nodule-like warts up to 2 µm high (enlarge the bottom illustration).

Given its vernal appearance and its size, comparison to Peziza badioconfusa is warranted; could my collections merely represent old specimens of the latter species, beginning to blacken? But the specimens in my collections are not particularly old, and plenty of black, but immature, specimens have been among them. Also, the nearly fusiform, delicately ornamented spores of badioconfusa are not even remotely similar.

I suspect that the cup fungus I've been collecting is what several North American authors have mistakenly called "Peziza brunneoatra." The latter species is a rare European fungus, characterized by dark surfaces and spores with comparatively low ornamentation that consists of isolated warts, rather than ridges. Beginning with Seaver (1928), North American authors have applied the name brunneoatra, which means "brown-black," to basically any mid-sized, blackish brown to black Peziza—a tradition also followed by many European taxonomists until fairly recently.

But type studies and investigations of more recent Peziza brunneoatra collections by van Vooren and collaborators (2018) have narrowed the contemporary concept of the species, which has spores ornamented with low, isolated warts; the authors conclude that "the North American concept of this species . . . clearly contradicts the data of our review and could represent another species or a mixture of different species."


Ecology: Probably mycorrhizal; growing gregariously in bare soil in hardwood forests; spring; distribution uncertain. The illustrated and described collections are from Illinois and Ohio.

Fruiting Body: Cup-shaped when young, remaining so in maturity, or becoming saucer-shaped; 1–3 (rarely 5) cm across; upper surface bald, dark brown to black, becoming a little wrinkled centrally, the margin blackening; undersurface finely fuzzy (with a hand lens) or nearly bald, dark brown to black; stem absent; attached to the substrate at a central location; flesh brown, brittle, not exuding juice when squeezed.

Odor: Not distinctive.

Spore Print: White (enlarge the 4th illustration to see spore print caused by the scanner's light).

Microscopic Features: Spores 15–20 x 8–12 µm including ornamentation (in one collection spores were smaller, 12–15 x 6–8 µm); more or less ellipsoid; at first smooth, but soon developing nodules and ridges up to 2.5 µm or more high, often arranged longitudinally, creating the impression of striae or a partial reticulum; developing large polar caps up to 4 µm wide and 3 µm high; in KOH hyaline to yellowish and 1- or 2-guttulate; in Melzer's yellowish to golden, with some ornamentation amyloid. Asci 8-spored; with amyloid tips. Paraphyses hardly exceeding the asci; 4–8 µm wide at the apex; apices subclavate to clavate; smooth; hyaline to yellow-brown (en masse) in KOH. Excipular surface of textura globulosa-angularis, appearing nearly hymeniform; terminal elements 20–40+ µm long, globose to ellipsoid or pyriform, smooth, hyaline to brownish in KOH.

REFERENCES: (Seaver, 1928; Dennis, 1968; Arora, 1986; Raymundo et al., 2012; Medel et al., 2013; van Vooren et al., 2018.) Herb. Kuo 05300401, 06241001, 06071301, 06082401.

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Peziza species 01

Peziza species 01

Peziza species 01

Peziza species 01

Peziza species 01
Asci in MLZ, developing spores

Peziza species 01

Peziza species 01

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