The Featured Mushroom for
December 2013 was
The Barometer Earthstar
a.k.a. Austraeus hygrometricus
The barometer earthstar is in the same class, Gasteromycetes, as the puffballs. In particular this earthstar is related to the order, Sclerodermatales, that contains the Sclerodermas like the poison pigskin puffball, Scleroderma citrinum or S. aurantium. Austraeus hygrometricus has a central, rounded spore sac, like puffballs, surrounded by a set of star-like rays. The rays bend backwards toward the ground when wet and curl back inward when dry protecting the spore sac. The name of the genius refers to the star shaped rays and the species epithet refers to the way the rays change with moisture.
The whitish spore sac with a rough skin is ½ to 1 ¼ inches across and is nearly round. With age the spore sac will develop a irregular tear on top to release spores. The spore mass is white becoming brown with age. The rays are 1 to 2 inches long and are formed when the outer wall of the spore sac splits into 6 to 12 sections. In wet weather the rays can bend back enough to raise the spore sac above the forest floor. The spore mass is reddish brown to brown when mature.
The barometer earthstar can be found in almost any habitat where mushroom can grow arranging from sand dunes to high mountains. The common name, of course, refers to the way this mushroom responds to changes in the weather.