Calvatia pachyderma

Sporocarp
Fruiting body subglobose, cushion-shaped, to turbinate, 6.0-11.0 cm tall, 7.0-13.0 cm broad, abruptly tapered towards the base, sometimes with a root-like attachment to the substrate; exoperidium persistent, thin, less than 1.0 mm thick, glabrous, pallid to pale greyish-tan, basal area dull purple-brown in age; endoperidium 2.0-3.0 mm thick, punky, brittle; gleba cream-colored, then ochre, eventually dull yellowish-brown, occasionally tinged olive, powdery; subgleba and sterile base absent; fruiting body opening by splits or polygonal fractures; odor of mushrooms; taste untried.

Spores
Spores 4.0-6.0 x 3.5-5.0 µm, subglobose to ovoid, mostly the latter, smooth, with a central oil droplet and a short, < 1.0 µm pedicel; spores dull yellowish-brown to tobacco-brown in mass; capillitium with round to oval pits.

Habitat
Solitary or in small groups in native grasslands or dry, open areas; fruiting shortly after the fall rains, again in the spring; known from coastal locations but probably occurs elsewhere at low elevations; occasional.

Edibility
Edible and good. Should be eaten only when young and firm with the gleba still pure white.

Comments
The principal fieldmark of this Calvatia, as the species name suggests, is a relatively thick peridium. Mycenastrum corium and Bovista pila are similar, though usually smaller. They mimic Calvatia pachyderma in lacking a sterile base, opening by cracks, and fruiting in grass. Mycenastrum corium can be differentiated by a tough, leathery, not brittle peridium, and a firm, not powdery gleba. It also has a distinctive capillitium, the main branches giving rise to short, antler-like stubs. Bovista pila can be distinguished by a thin, parchment-like endoperidium, usually with a purple-brown metallic sheen, and a capillitium composed of thick-walled, more or less dichotomously branched individual elements.