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Geastrum saccatum

Geastrum saccatum
Geastrum 20070721.jpg
Scientific classification
Kingdom: Fungi
Phylum: Basidiomycota
Class: Agaricomycetes
Subclass: Phallomycetidae
Order: Geastrales
Family: Geastraceae
Genus: Geastrum
Species: G. saccatum
Binomial name
Geastrum saccatum
Fr.
Geastrum Saccatum
Mycological characteristics
glebal hymenium
no distinct cap
spore print is brown
ecology is saprotrophic
edibility: inedible

Geastrum saccatum, commonly known as the rounded earthstar, is a species of mushroom belonging to the Geastrum genus. It has a worldwide distribution and is found growing on rotting wood. It is considered inedible by mushroomers because of its bitter taste. It is a common mushroom, but collections are at their peak during late summer. 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. In Brazil, its common name translates to "star of the land".

The immature fruiting body is 0.6 to 2.5 centimetres (0.24 to 0.98 in) in diameter and 0.8 to 1.5 centimetres (0.31 to 0.59 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 several rays that curve backward (recurve) to the base. The mushroom is 2 to 5 centimetres (0.79 to 1.97 in) in diameter after the rays have expanded. Unlike some other members of the genus Geastrum (such as Geastrum 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 centimetres (0.20 to 0.79 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 spores are rounded, with warts, and have dimensions of 3.5–4.5 µm.


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