Geaster

Geastrum
Geastrum triplex
Geastrum saccatum
Scientific classification
Kingdom:	Fungi
Division:	Basidiomycota
Class:	Agaricomycetes
Subclass:	Phallomycetidae
Order:	Geastrales
Family:	Geastraceae
Genus:	Geastrum Pers.
Type species
Geastrum pectinatum Pers.
Species
About 50; See text

About 50; See text

Geastrum (orthographical variant Geaster) is a genus of mushroom in the family Geastraceae. Many species are known commonly as earthstars.

The name comes from geo meaning earth and aster meaning star.

The name refers to the behavior of the outer peridium. At maturity, the outer layer of the fruiting body splits into segments which turn outward creating a star-like pattern on the ground. The inner peridium is a spore sack. In some species, the outer peridium splits from a middle layer, causing the spore sack to arch off the ground. If the outer peridium opens when wet and closes when dry, it is described as hygroscopic.

In some species, the inner peridium is borne on a stalk or pedicel. The columella is a column-like clump of sterile tissue to be found inside the inner peridium. The network of fertile tissue inside the inner peridium, the capillitium, arises from the columella. The mouth in most species of "earth-stars" is quite prominent, often arising as a small cone at the apex of the inner peridium. It may be even or sulcate (grooved).

They are generally not toxic but considered non-edible due to their fibrous texture in the mature stage that they are generally found at.

Although the Dictionary of the Fungi (2008) estimated roughly 50 species in Geastrum, a more recent estimate (2014) suggests that there may be up to 120 species. Some similar species that are otherwise difficult to differentiate using classical morphological features (such as G. triplex, G. saccatum, and G. lageniforme) can be identified using chemical spot tests that detect phenoloxidase enzymatic activity, as well as differences in the crystal structure of calcium oxalate deposits. Species include:

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