Geastrum triplex

Appearance

Like all mushrooms, the fruit body of ''Geastrum triplex'' is the visible part of a larger organism. Hidden from sight are masses of nearly invisible fungal threads called mycelium, which form the active feeding and growing structures of the fungus.

The fruit body—created when environmental conditions such as temperature, moisture, and nutrient availability are optimal—is designed to produce and disseminate spores. ''Geastrum triplex'' has the largest fruit body of the earthstar mushrooms. The immature fruit body is typically 1 to 5 cm in diameter, and up to 8 to 9 cm broad after the rays have spread out. It is composed of a roughly spherical to egg-shaped structure, the endoperidium, topped by an opening, the ostiole, covered by fragments of tissue that form a small pointed beak.

The endoperidium is typically lacking any sort of stem grayish brown to "wood brown" when young but light yellow-brown in dried, unopened specimens. The outer tissue layer, the exoperidium, develops splits which radiate from the apex and form between four and eight rays that separate from the endoperidium. The latter's thin and papery envelope surrounds a mass of spores and fertile tissue known as the gleba. The central part of the gleba contains a pseudocolumella , that is typically cylindrical or club-shaped, and extends up from the base. Because of the variability in columella persistence, size, structure and shape within the genus, its value for identification is limited.

The exoperidium's rays are 2 to 4 cm long and up to 4 mm thick. The outer surface of the rays and unopened specimens have a rough texture. In several ''Geastrum'' species, dirt and debris adhere to the underside, this is not the case in ''G. triplex''. The inner fleshy layers of these rays are near "wood brown" in color when dried, and have a layer of surface tissue that cracks into patches. There is a great deal of variation, however, to the extent in which the upper surface tissue of the rays crack: this tissue layer may also remain closely attached as a sheet over the unsegmented part of the outer wall with the part adhering to the rays variously cracked and sometimes finally peeling off in places.

Distribution

''Geastrum triplex'' has a widespread distribution, and has been collected in Asia, Australia, Europe, and Africa. In North America, its range extends north to Canada and south to Mexico, including the whole continental United States and Hawaii. In Central and South America the fungus has been reported from Panama, Trinidad and Tobago, Argentina, Brazil, and Chile.