Common Name: Earthstar
Fruiting body puffball-shaped at first, 1-2.5 cm wide, the peridium splitting into 5 to 8 rays yielding a final diameter of approximately 5 cm.; rays, thick, fleshy, upper surface pinkish-tan to yellow-brown, recurving from the base; spore sac sessile, 0.5-2.0 cm broad, round, smooth, brown rupturing via an apical pore, the latter surrounded by a small but well-defined slightly depressed disc.
Spores 3.5-4.5 µm, nearly round, warted. Spores dark-brown in mass.
Solitary to scattered from late fall to early spring in mixed hardwood & coniferous forests.
Inedible, at least when mature.
Geastrum saccatum is distinguished from the several species of earthstars that occur in the S.F. Bay area by its sessile spore sac which has a small depressed disc surrounding the apical pore, and recurved non-hygroscopic rays. Geastrum triplex is similar but the spore sac sits in a shallow cup formed from splitting of peridial wall tissue; Geastrum fimbriatum also has a sessile spore sac, but the apical pore is not surrounded by a well defined depressed disc; Geastrum fornicatum has a spore sac with a short stalk and stands erect from the substrate on the tips of its rays, while Astraeus hygrometricus and A. peteridis are told apart by their hygroscopic rays.