rounded earthstar

The immature fruiting body is 0.6 to 2.5 centimetres (1⁄4 to 1 in) in diameter and 0.8 to 1.5 cm (3⁄8 to 5⁄8 in) tall. Initially, the fruiting body is egg-shaped—similar in appearance to puffballs—and has strands of mycelia (rhizomorphs) at the base that attach it to the growing surface. The 'skin,' or peridium, is composed of two separate layers: the outer layer (exoperidium), which is a golden tan to yellowish-brown color, separates away from the inner basidiocarp and splits into five to eight rays that curve backward (recurve) to the base. The mushroom is 2 to 5 cm (3⁄4 to 2 in) in diameter after the rays have expanded. Unlike some other members of the genus Geastrum (like G. fornicatum), the arms do not push the basidiocarp off the ground; rather, it lies flat. The inner spore-bearing basidiocarp is 0.5 to 2 cm (1⁄4 to 3⁄4 in) broad, and has a central pore surrounded by a circular dull-brown apical disc; the disc is distinctly ridged or depressed. The inside of the interior sphere is white when young, but matures into a mass of brown, powdery spores mixed with thick-walled fibres known as capillitium. The flesh is bitter.

Spores. The spores are rounded, with warts, and have dimensions of 3.5–4.5 μm.

Mechanism of dehiscence. …

Geastrum saccatum is saprobic, and grows scattered or clustered together in leaf litter of humus, usually in late summer and fall. It has a cosmopolitan distribution, and is well adapted to tropical regions. It is common in Hawaiian dry forests. The species has been collected in North America (Canada, the United States and Mexico), Central America (the Congo and Panama), South America (Argentina, Uruguay, and Brazil), Cuba, Africa (Tanzania, West Africa, and South Africa), Asia (China and India), and Tobago and Toowoomba, QLD, Australia. In North America, it is found September–December on the west coast and July–October elsewhere.