Rounded earthstar

Appearance

The immature fruiting body is 0.6 to 2.5 centimetres in diameter and 0.8 to 1.5 centimetres tall. Initially, the fruiting body is egg-shaped–similar in appearance to puffballs–and has strands of mycelia at the base that attach it to the growing surface.

The 'skin,' or peridium, is composed of two separate layers: the outer layer, which is a golden tan to yellowish brown color, separates away from the inner basidiocarp and splits into several rays that curve backward to the base. The mushroom is 2 to 5 centimetre in diameter after the rays have expanded.

Unlike some other members of the genus ''Geastrum'' the arms do not push the basidiocarp off the ground; rather, it lies flat. The inner spore-bearing basidiocarp is 0.5 to 2 centimetres 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.

Naming

The related species ''Geastrum fimbriatum'' does not have an apical disc, and its pores are slightly smaller. ''G. saccatum'' may be distinguished from ''G. indicum'' by the absence of loose tissue forming a collar around the base of the endoperidium.

Distribution

''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 the United States, Argentina, Uruguay, Brazil, Canada, China, Congo, Cuba, Mexico, Panama, South Africa, West Africa, Tanzania, and Tobago.