Geastrum saccatum

Geastrum saccatum, commonly known as the sessile earthstar or rounded earthstar, or star of the land, is a species of mushroom belonging to the genus Geastrum. The opening of the outer layer of the fruiting body in the characteristic star shape is thought to be due to a buildup of calcium oxalate crystals immediately prior to dehiscence. G. saccatum is distinguished from other earthstars by the distinct circular ridge or depression surrounding the central pore.

The species has a worldwide distribution and is found growing on rotting wood. It is a common mushroom, but peaks in popularity during late summer. It is considered inedible but contains bioactive compounds.