Today we feature the fungus Geastrum triplex, commonly known as the saucered or collared earthstar. These images (image 1 | image 2) were taken recently at the State Botanical Garden of Georgia and uploaded to the Botany Photo of the Day Flickr Pool by Hugh Nourse (aka Hugh and Carol Nourse@Flickr). Thanks for sharing, Hugh!
Geastrum triplex, of the Geastraceae, is an earthstar fungus. The earthstars are comprised of the genera Geastrum, Astraeus, and Myriostoma. Earthstars are modified puffballs that have a thick outer skin that splits into star-like rays (Geastrum saccatum was featured on Botany Photo of the Day in 2011). The rays, after splitting, often curve to expose the spore case (inner skin) for spore dispersal. Some earthstars are hygroscopic, though, most geastrums (including Geastrum triplex) are not. After the rays split, the central region of Geastrum triplex often (not always) breaks loose to form a broad cup or saucer around the flattened spore case. The spore case of the saucered earthstar is not elevated on a stalk (like others in the genus), and holds powdery, brown spores that are round and warted.
Geastrum triplex is a saprobic (feeding on dead or decaying matter) fungus that is widely distributed across North America. It grows alone or in groups in forest humus, often under hardwood trees. This species (like all earthstars) is noted to be difficult to find when immature because individuals are inconspicuous, and often develop underground. If you do happen to find this fungus when it is young (white inside), it is considered edible according to Mushrooms Demystified by David Arora. When they are older (and easier to find), they are apparently often too tough and fibrous to eat.