Wikipedia:Today's featured article/December 16, 2015

Geastrum quadrifidum, commonly known as the rayed earthstar, is an inedible species of mushroom belonging to the genus Geastrum, the earthstar fungi. First described by Christian Hendrik Persoon in 1794, it is a cosmopolitan but uncommon species found in Europe, the Americas, Africa, Asia, and Australasia. The fungus feeds off decomposing organic matter in the litter and soil of coniferous forests. The small, grayish-brown fruit bodies are enclosed by a skin, or peridium, made up of four layers of tissue. The outer layer splits to form star-like rays and expose a spore case, inside of which is the gleba—fertile spore-producing tissue. The spore case, set on a short, slender stalk, has a well-defined narrow pore at the top through which mature spores escape. The mushroom's outer skin is purplish-brown, with four or five cream or yellowish-brown rays whose tips are stuck in the substrate. This species is one of several earthstars whose rays arch downward as they mature, lifting the spore sac upward and allowing it to catch air currents that disseminate the spores.