Peziza domiciliana
This brownish cup fungus surprises people by appearing in their houses, often through cracks in concrete or masonry. It is also found in sandstone and in crumbling building remains, as well as in carpets, plaster, shower stalls, and so on. Peziza domiciliana is not the only species of Peziza that could conceivably grow in such settings, but it is the species that is usually found indoors or in concrete. Identification to a scientific certainty, therefore, requires microscopic analysis (see the list of microscopic features below).
Edibility is not known for Peziza domiciliana; do not experiment.
Description:
Ecology: Saprobic, growing alone or gregariously in indoor settings or outside in garages, concrete rubble, coal bins, sand, and so on; year-round; widely distributed in North America.
Fruiting Body: When young goblet-shaped, with a short stem; in age flattening out to become irregularly saucer-shaped (but usually retaining a depressed center); 2-10 cm wide; upper surface at first whitish, darkening to pale brown, smooth or wrinkled; under surface usually slightly paler; flesh pale, sometimes bruising slowly yellowish; odor not distinctive; often surrounded by whitish mycelium.
Microscopic Features: Spores 11-15 x 6-10 µ; smooth or slightly roughened at maturity; without oil droplets or with 2 small droplets. Asci eight-spored; with blue tips in Melzer's Reagent; up to 250 x 12 µ. Paraphyses slender; septate; with swollen tips.