Geastrum quadrifidum

What You Should Know

Geastrum quadrifidum is an inedible mushroom belonging to the genus Geastrum, or Earth star mushroom. First scientifically described by Christian Hendrik Persoon in 1794, G. quadrifidum is a cosmopolitan but uncommon species in Europe, America, Africa, Asia and Oceania. Fungi are saprophytes that feed on decomposing organic matter present in soil and coniferous forest debris.

The small, tough fruiting bodies are gray-brown spheres, initially surrounded by skin or capsule, and composed of four distinct layers of tissue. The outer layers of the tissue split open to form star rays, exposing the circular spore shells. Inside the spore box are gleba - fertile tissue that produces spores that are white and hard when young but turn brown and powdery with age. The gray-brown spore coat is located on a short, slender stem with a clear, narrow hole at the top through which mature spores can escape.

Fully expanded, the fruit body reaches dimensions up to 2–3 cm (0.8–1.2 in) wide and up to about 3 cm (1.2 in) tall. The outer skin is purplish-brown, with four or five cream or yellowish-brown colored rays that have their tips stuck in the substrate. There is a flat mat of interwoven mycelia between ray tips. The spores are spherical, warty, and have a diameter of up to 6 μm. Geastrum quadrifidum is one of several earthstars whose rays arch downward as they mature, lifting the spore sac upward, high enough to catch air currents that disseminate the spores into new habitats. The species is easily confused with Geastrum fornicatum, larger earthstar without a well-defined pore mouth.

Other names: Rayed Earthstar, Four-Footed Earthstar.

Geastrum quadrifidum Mushroom Identification

1. Fruit Bodies

   up to 2 cm in diameter, rounded shape, with a short-conical top, after opening the diameter of the fruit body reaches 3-4 cm.

2. Outer Shell

   The exoperidium (outer shell) is hard, three-layered, white or whitish, both externally and internally, when ripe it breaks into 4 (8) pointed blades that bend downwards, raising the glebe above the soil level, sometimes the exoperidium is divided into two additional layers, which at the ends of the blades remain undivided.

3. Inner Shell

   Endoperidium (inner shell) single-layered, papery, cervically narrowed under the glebe, thin, smooth or fibrous, grayish-blue, bluish-gray, whitish, brownish, blackish, located on a short, whitish, cervically narrowed, flattened stem, with a disk-like expansion – an apophysis, with a cone-shaped, fibrous-ciliated, radial-fibrous peristome, with an opening for the release of the spore mass.

4. Spore-Bearing Layer

   The soil (spore-bearing layer) is 0.9–1.3 cm high, 0.5–1.2 cm in diameter, dark brown or purplish-brown, and dusty when ripe.

5. Spores

   3.5-6 μm, rounded, with a warty surface, light brown or brown.

6. Spore Print

   Dark brown with a purple tint.

7. Habitat

   It grows from August to October, in coniferous and mixed forests, with pines and spruces, on sandy soils, and on coniferous and deciduous litter. Dried fruiting bodies are stored until the spring of the following year.

Geastrum quadrifidum Look-Alikes

G. fornicatum (left) and G. pectinatum (right) are also fornicate earthstars.

Geastrum quadrifidum is readily confused with G. fornicatum, which is larger—up to 15 cm (5.9 in)—and has smaller spores (4–5 μm in diameter). Geastrum minimum, although small like G. quadrifidum, is distinguished by having more rays (usually more than seven), and it is not fornicate. Also, its mycelial layer is attached to the fibrous layer for a long time, without forming a mycelial cup like G. quadrifidum. The Chilean species G. jurei does not have a clearly demarcated peristome.

Geastrum quadrifidum is also similar to G. dissimile, G. leptospermum, and G. welwitschii in its fruit body morphology, especially the exoperidial rays, endoperidial body, and peristome. Geastrum dissimile differs from G. quadrifidum by its often sulcate or silky fimbriate, smooth peristome, and slightly smaller spores (4–5 μm in diameter). Geastrum leptospermum can be distinguished from G. quadrifidum by its smaller spores (2–3 μm in diameter), and by its preference for growing in mosses on tree trunks. G. welwitschii differs from G. quadrifidum by its epigeal mycelial cup with a felted or tufted outer surface, and indistinctly delimited peristome.

Geastrum quadrifidum Taxonomy and Etymology

The Dutch mycologist Christian Hendrik Persoon published the first official description of Geastrum quadrifidum in 1794, and later sanctioned this name in his 1801 Synopsis Methodica Fungorum (as Geastrum quadrifidum var. minus, a variety now considered synonymous with G. quadrifidum). Although the species had been previously described as Lycoperdon coronatum by Jacob Christian Schaeffer (1763) and Giovanni Antonio Scopoli (1772), then afterward as Geaster coronatus by Joseph Schröter (1889), the epithet coronatus is not to be used because of the existence of the sanctioned name.

In Japan, G. quadrifidum has occasionally been called "Geastrum minus" (Pers.) G. Cunn. (for example, as in Imai, 1936); within taxonomical terminology, this usage is an auctorum non—a misapplication or misinterpretation of the species name.

According to Stanek's classification of the genus Geastrum, (a classification later endorsed in Sunhede's 1989 monograph of European Geastrum species), G. quadrifidum belongs in the subsection Glabrostoma of the section Perimyceliata, a grouping of similar Geastrum species that incorporate and encrust debris in the mycelial layer, and have an even peristome (opening) that is fibrillose (made of more or less parallel thin thread-like filaments). Several common names for G. quadrifidum have been suggested, including "rayed earthstar", "four-pointed earthstar" and "four-footed earthstar". Samuel Frederick Gray called it the "four-cut shell-puff" in his 1821 The Natural Arrangement of British Plants, but the name was not adopted by subsequent authors. The specific epithet quadrifidum is derived from Latin, and means "four-forks".

Geastrum quadrifidum Synonyms

1. Geastrum coronatum (Scop.) J.Schröt., 1889, nom. illeg.

2. Geastrum quadrifidum var. minus Pers., 1801

3. Geastrum minus (Pers.) G.Cunn., 1926

4. Lycoperdon coronatum Scop., 1772

5. Lycoperdon secundum Schaeff., 1763, nom. inval.

Sources:

Photo 1 - Author: Adrien BENOIT à la GUILLAUME (Creative Commons Attribution-Share Alike 4.0 International)

Photo 2 - Author: Sasata (Creative Commons Attribution 3.0 Unported)

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