Stropharia semiglobata
Description
Protostropharia semiglobata (Psilocybe semiglobata) is an agaric fungus of the family Strophariaceae. A widespread species with a cosmopolitan distribution, the fungus produces mushrooms on the dung of various wild and domesticated herbivores. The mushrooms have hemispherical straw yellow to buff-tan caps, grayish gills that become dark brown in age, and a slender, smooth stem with a fragile ring.
Protostropharia semiglobata is described in some field guides as edible and in others as inedible or suspect. Since they grow on dung and that some fungi in this genus are known to be at least moderately poisonous, we recommend that this species should be regarded as a toxic toadstool.
Common names: Dung Roundhead, The Halfglobe Mushroom, Hemispheric Stropharia.
Mushroom Identification
Cap
The hemispherical cap of the Dung Roundhead is 1 to 3cm in diameter. It is viscid when wet; smooth and shiny when dry. The thin cap flesh is very pale.
Gills
At first pale clay-brown, the moderately spaced adnate gills of Stropharia semiglobata darken to cinnamon with pale edges as the spores mature.
Stem
Concolorous with the cap, 2 to 3mm in diameter and 5 to 10cm tall, the smooth, slender stem of the Dung Roundhead is very pale at the apex and pale ochre below the transient ring; its flesh is solid and pale ochre.
The ring zone is white at first but discolors purple-brown as the fruitbody ages and spores are released from the gills.
Spores
Ellipsoidal to ovoid, smooth, 15-19 x 9-11μm; thick-walled; with a small apical germ pore - most clearly visible in the spores at top left and bottom left as a thin region in the outer wall at the sharper (apex) end of the ovoid spore.
Spore Print
Purple-brown.
Habitat & Ecological Role
Protostropharia semiglobata is saprobic on animal dung and freshly manured grassland.
Look-Alikes
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Also occurs on dung; it retains its stem ring and provides a black spore print.
Deconica coprophila and its close cousin Deconica merdaria
Differs in having reddish-brown to brown sub-viscid caps and lack of a ring.
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Has a grayish-brown, fringed, non-viscid cap and also lacks a ring.
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Larger, annulate species with a cream-colored, distinctively wrinkled, viscid cap.
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Differs in possessing a non-viscid, striate-margined annulus, and has brown, not purple-brown gills and spores.
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Occasionally fruits on dung. It has a viscid, yellowish cap with a striate margin, ochre-colored gills, and lacks a veil.
History
In 1786 by August Johann Georg Karl Batsch (1761-1802) named it Agaricus semiglobatus.
After being moved through several other genera, the Dung Roundhead was finally settled into its present taxonomic position in 1872 with the help of the French mycologist Lucien Quélet.
In 2013 American mycologist Scott Redhead and colleagues proposed a new genus, Protostropharia, to contain those Stropharia species in which astrocystidia rather than crystalline acanthocytes form on their mycelia; Redhead has made Protostropharia semiglobata the type species of this proposed genus. Kew and the British Mycological Society in their checklists of fungi have now adopted the Protostropharia separation, and so Stropharia semiglobata (Batsch) Quél. is a deprecated scientific name of this species in Britain.
Synonyms of Protostropharia semiglobata include Agaricus semiglobatus Batsch, Agaricus stercorarius Schumach., Agaricus virosus Sowerby, Coprinus semiglobatus (Batsch) Gray, Stropharia stercoraria (Schumach.) Quél., Stropharia semiglobata var. stercoraria (Schumach.) Bon, Psilocybe semiglobata (Batsch) Noordel., and Stropharia semiglobata (Batsch) Quel.
Proto- means first, while stropharia means with a belt - surely a reference to the stem rings of Stropharia species - while the specific epithet semiglobata means just what it sounds like - half a globe (hemispherical, therefore).
Photo sources:
Photo 1 - Author: Dr. Hans-Günter Wagner (CC BY-SA 2.0)
Photo 2 - Author: Jason Hollinger (CC BY-SA 3.0)
Photo 3 - Author: Dr. Hans-Günter Wagner (CC BY-SA 2.0)
Photo 4 - Author: Dr. Hans-Günter Wagner (CC BY-SA 2.0)
