Myriostoma coliforme (Dicks.) Corda (1842)

Commonly called the Saltshaker earthstar, or in some areas, the Pepper Pot.

This fungus features a roundish ball called a head or a peridium containing spores. This ball sits on small stalks on top of star-like rays. When immature or dry, the rays (also called the outer peridium or exoperidium) enclose the endoperidium (inner peridium). When the basidiocarp gets wet, the exoperidium splits and folds back, forming the star-shaped structure. The inner peridium remains closed and this is where the spores are formed.

Unlike true puffballs, the basidia where the spores grow are not arranged in a hymenium. Instead the basidia form throughout the entire inside of the head. This spore mass is called the gleba. The gleba becomes powdery with age and the spores are dispersed through holes in the peridium called mouths or pores.

When the mushroom gets dry the star-like rays will fold back up around the endoperidium until it rains again, then they fold back out and the rain droplets can hit the walls of the endoperidium. The force of the droplets ejects spores out of the pores. This behavior allows the fungus to disperse its spores during moist conditions which increases the chance that they will be able to germinate.

Etymology: From Latin, “like a colander”

Previously known as:
 Lycoperdon coliforme Dicks. (1776)
 Geastrum coliformis (Dicks.) Pers. (1801)

(Taxonomy from Index Fungorum )

Widely distributed in North America. Also reported from South America and Europe, most likely found in other parts of the world as well. Most sources indicate that this species is rare. It is the only species in the genus Myriostoma.

Endoperidium: 1.5-7 cm wide, papery, spherical, sometimes flattened. Features several pores or mouths on upper surface which is grayish brown in color. Gleba is white when young, becoming brown and powdery with age, divided into loculi, each of which opens into an ostiole to release spores. Capillitial threads are free and simple.

Stalk: Several short, small stalks connect inner peridium to outer peridium.

Exoperidium: usually 5 to 12 rays, 1-6 cm long, light brown to brownish gray in color. Covering the endoperidium when young, splitting into rays with maturity, and opening/expanding when wet. Exoperidium is actually two layers, the upper layer being the mesoperidium. These two layers don’t easily separate and sometimes are indistinguishable.

Spores: Reddish-brown, spherical, heavily warted, 4-6 um in diameter.

Several Geastrum and Astraeus earthstars look similar. However, Myriostoma coliforme is the only earthstar that has many mouths on the inner peridium, so this is the most distinguishing characteristic to use to separate it from the others. It also is the only earthstar that features several short stalks connecting its inner and outer peridiums (other earthstars sometimes have one stalk, but never several).

See Tom Volk’s page on earthstars.

When young, before the outer peridium has split open, earthstars can resemble puffballs. Myriostoma features 3 peridial layers (the mesoperidium is often inseparable from the exoperidium, but is usually distinct), where as true puffballs only have 2 peridial layers. Also, true puffballs feature basidia arranged in a hymenium, and their spores are usually smooth.

See Tom Volk’s page on puffballs.

Likes to grow in dry woodlands, and in sandy soil in open areas. Solitary or in small groups.

Can be used for decoration because of its aesthetically pleasing appearance. It also plays important roles in the environment, although its exact ecological niche has not been determined with certainty.