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Geastrum saccatum
Fries
Syst. Myc. 3: 16. 1829.
Common Name: Earthstar
Sporocarp
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
Spores 3.5-4.5 µm, nearly round, warted. Spores dark-brown in mass.
Habitat
Solitary to scattered from late fall to early spring in mixed hardwood & coniferous forests.
Edibility
Inedible, at least when mature.
Comments
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.
References
Calonge, Francisco D. (1998). Flora Mycologica Iberica. Vol. 3. Gasteromycetes, I. Lycoperdales, Nidulariales, Phallales, Sclerodermatales, Tulostomatales. J. Cramer: Berlin, Germany. 271 p.
Smith, A.H. (1951). Puffballs and Their Allies in Michigan. University of Michigan Press: Ann Arbor, MI. 131 p.
Sunhede, Stellan (1989). Geastraceae (Basidiomycota) -- Morphology, Ecology, and Systematics with Special Emphasis on Northern European Species. Fungiflora: Oslo, Norway. 535 p.
Other Descriptions and Photos
- Taylor F. Lockwood: Geastrum saccatum (CP) -- immature sporocarp, before the outer peridium begins to split into rays
- Taylor F. Lockwood: Geastrum saccatum (CP) -- sporocarp just beginning to open
- Taylor F. Lockwood: Geastrum saccatum (CP) -- open sporocarp
- Taylor F. Lockwood: Geastrum saccatum (CP) -- older specimen with rays lifting sporocarp from substrate; note sessile spore sac
- Michael Wood: Geastrum saccatum (CP)

- Boleslaw Kuznik -- Hunting for Mushrooms: Geastrum saccatum (CP)
- George Barron's Fungi of Canada (East): Geastrum saccatum (D & CP)
- Eileen's Mushroom Mania: Geastrum saccatum (CP)
- Mushroom Observer: Geastrum saccatum (CP)
- Arora (1986): p. 703 (D), p. 704 (P)
- Lincoff: p. 818 (D), plate 636 (CP)
- McKenny et al.: p. 193 (D & CP)
- Miller: sp. 350 (D & CP)
- Phillips: p. 286 (D & CP)
(D=Description; I=Illustration; P=Photo; CP=Color Photo)
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