Mycenastrum is a fungal genus in the family Agaricaceae. The genus is monotypic, containing one widely distributed species, Mycenastrum corium, known by various common names: the giant pasture puffball, leathery puffball, or tough puffball. The roughly spherical to turnip-shaped puffball-like fruit bodies grow to a diameter of 6–24 cm (2–9 in). Initially covered by a thick, felted, whitish layer, the puffballs develop a characteristic checkered skin (peridium) in age. As the spores mature, the gleba turns first yellowish then purplish brown. Spores are released when the peridium eventually splits open into irregularly shaped sections. Microscopically, the gleba consists of spherical, dark brown spores with rounded bumps on their surfaces, and capillitia—masses of intricately branched fibers—that form long thornlike spines. The puffball grows on or in the ground in prairie or desert habitats. Although widely distributed, it is not commonly encountered. It is a threatened species in Europe. When the internal spore mass (the gleba) is firm and white, the puffball is edible, although some individuals may suffer mild gastrointestinal symptoms after eating it.
Taxonomy The species was originally described in 1805 as Lycoperdon corium in the second volume of Augustin Pyramus de Candolle and Jean-Baptiste Lamarck's Flore Française. They attributed authorship to French botanist Louis Ben Guersent, who discovered it in an alfalfa field between the town of La Sotte and Rouen in northern France. Synonyms include Scleroderma corium, published by Arthur Harmount Graves in 1830, and Steerbekia corium, published by Elias Magnus Fries in 1849. The species was given its current name by Nicaise Auguste Desvaux in 1842, who circumscribed the genus Mycenastrum to contain it. Generic synonyms are Vassilii Czernajew's 1845 Endonevrum and Stephan Schulzer von Müggenburg's 1876 Pachyderma. In 1948, Sanford Myron Zeller circumscribed the new family Mycenastraceae, containing both Mycenastrum as the type genus, and Bovista. A 2001 molecular study supported the inclusion of Mycenastrum corium in the Lycoperdales, where it was traditionally placed. In a more recent (2008) cladistic analysis, Mycenastrum was shown to be a sister group to the Lycoperdaceae; authors Larsson and Jeppson agreed with Zeller (1949) and Pilat's (1958) decision to regard Mycenastrium as a monotypic genus in the separate family Mycenastraceae. Despite this, several taxonomic authorities prefer to fold Mycenastraceae into the Agaricaceae. It is commonly known as the "leathery puffball", the "tough puffball", or the "giant pasture puffball". María Homrich & Jorge E. Wright published the variety M. corium var. diabolicum in 1973 from South America. M. corium subspecies ferrugineum was described in 2005 from Jefferson County, Colorado, by Orson K. Miller.
Former Mycenastrum Most species historically named as Mycenastrum have since been transferred to other genera, usually Scleroderma, but also Glyptoderma, Bovista, and Gastropila. Many, including those species that have not been reclassified are poorly known; the nomenclatural authority Index Fungorum considers only four of these former Mycenastrum species to be currently valid: Bovista bovistoides, B. lycoperdoides, Gastropila fragilis, and Glyptoderma coelatum.
Description
The gleba is white when young and has a cheesy appearance and consistency. As the puffball matures, it undergoes a lytic process involving water loss. Subsequently, the gleba becomes olivaceous, olive-brown, and finally, dark olive when dry, and then develops a characteristic pungent smell. The fruit body usually grows to a diameter of 6–15 cm (2–6 in), although extremes of 3 cm (1.2 in) and 27 cm (11 in) have been reported. Its shape ranges from roughly spherical, to obovate (egg-shaped) or pyriform (pear-shaped), sometimes plicate (crumpled, wrinkled) around a somewhat fibrous, persistent tuft of mycelium. The puffball is initially covered by a thick, felted, whitish layer (the exoperidium). This is continuous at first but eventually cracks and peels away in thin flakes, exposing a leathery to corky, nearly smooth, light brown to dark pinkish-brown surface. This tough layer of tissue (the endoperidium) measures about 2 mm thick and encloses the gleba. In maturity, the endoperidium opens by irregular splits that eventually extend towards the base in a star-shaped manner. These torn segments of endoperidium sometimes turn inside out, sometimes drying rigid, exposing a felt-like internal surface. Fruit bodies that grow underground have a conspicuously different morphology–a smooth, chocolate-brown coloured surface that lacks the patches characteristic of above-ground fruit bodies, and their capillitia are bifurcate with stumpy spines. The odor and taste of the species have been described as pungent or earthy and its taste astringent. Its spores are spherical, measuring 8–13 μm, and have a surface of irregular, coarse warts. The capillitia comprise late-maturing, thick-walled cells in the gleba. The main axes of these branched cells are 20–30 μm thick, and they are covered with numerous spines. Mycenastrum corium subsp. ferrugineum has a deep rusty red to reddish orange gleba, clearly distinguishing it from the glebal coloring of the main subspecies. M. corium var. diabolicum has an extremely spiny capillitium.
Puffball maturation
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