Scleroderma polyrhizum

Description
Mushroom Identification
Look-Alikes
History
Synonyms

Description

Scleroderma polyrhizum is a basidiomycete fungus and a member of the genus Scleroderma, or "earthballs". Found in dry, sandy soils, this species begins completely buried before slowly forcing the soil aside as it cracks apart to form a rough, star-shaped body with a diameter of 12–15 cm (4.7–5.9 in). At the center is the dark, brownish spore mass. Widely distributed wherever the soil and climate are favorable, it is known from Asia, Europe, and the Americas.

Growing completely buried, before slowly forcing itself to the surface and pushing the sand aside. As the mushroom matures and reaches the surface, the peridium (outer skin) cracks apart to form a rough star shape exposing an inner spore mass. The peridium is tough and thick, with a rough surface. Although it is white initially, it changes to light brown as it matures.

The fruitbodies of Scleroderma polyrhizum have been used in traditional Chinese medicine for the treatment of detumescence and hemostasis (Gong et al., 2005).

It is highly toxic, may be fatal if eaten. The size, thickness, and firmness of the fruiting body make this a readily identifiable fungus. They contain the steroid compounds ergosta-4,6,8(14) 22-tetraen-3-one and 5α,8α-epidoxyergosta-6,22-dien-3β-ol as well as palmitic acid and oleic acid.

Common names: Dead Man's Hand, Earthstar Scleroderma, Many-rooted Earthball.

Mushroom Identification

Ecology

Probably saprobic, but possibly mycorrhizal; growing alone, scattered, or gregariously in the grass and disturbed-ground settings; often appearing in urban settings; summer, fall, and early winter; widely distributed in North America.
Fruiting Body

8-13 cm across before splitting and spreading; round or nearly round; very tough; partially submerged in the ground; surface when young fairly smooth, often covered with whitish down; with age becoming pocked, pitted, or minutely scaly in places, and usually covered with adhering soil and debris; often bruising reddish or yellowish when rubbed; with maturity splitting near the top and peeling back in irregular rays to expose the spore mass; skin to 5 mm thick or more, whitish but blushing pink when sliced; sometimes with white rhizomorphs attached to the base; odor not distinctive.
Spore Mass

Black to purplish-black and hard at first, becoming dark brown and powdery; with whitish to pale yellowish threads interspersed.
Chemical Reactions

Fresh surface negative or slightly yellowish with KOH.
Microscopic Features

Spores 7-10 µ; round or nearly so; with very tiny spines (mostly under .5 µ); partially but not completely reticulate.

Look-Alikes

Scleroderma texense

Has a fruitbody similar in appearance to S. polyrhizum.
Scleroderma cepa, Scleroderma laeve, and Scleroderma albidum

Have non-reticulate spores.
Scleroderma areolatum and Scleroderma verrucosum

Have distinct scales, non-reticulate spores and dehiscence are rarely star-like.
Scleroderma floridanum

Has a surface covered in irregular scales and cracks (Sims).
Scleroderma citrinum

Has scales in rosettes and spores that often but do not always have a well-defined reticulum (Sims).
Scleroderma bovista and Scleroderma hypogaeum

Have larger spores with a well-defined reticulum.

History

The species was first described by Johann Friedrich Gmelin in 1792 as Lycoperdon polyrhizum. Christiaan Hendrik Persoon transferred the species to the genus Scleroderma in his 1801 work Synopsis methodica fungorum. Elias Fries's Scleroderma geaster (published in 1829) is a synonym; the epithet geaster refers to the similarity with earthstar fungi of the genus Geastrum. In 1848, Joseph-Henri Léveillé considered the star-shaped opening of mature fruit bodies to be a distinct characteristic and proposed the genus Sclerangium to contain the taxon.

According to the classification of Scleroderma proposed by Gastón Guzmán in 1970, Scleroderma polyrhizum is placed in the subgenus Sclerangium, which includes species with partially reticulate spores.