Clitocybe rivulosa

What You Should Know

Clitocybe rivulosa is a poisonous fungus that belongs to a large group of mushrooms called Clitocybe. It is a small, white, funnel-shaped fungus that grows in lawns, meadows, and other grassy areas in Europe and North America. When it dries out, it turns pure white and becomes harder to identify. This characteristic is known as hygrophanous, but it should not be confused with smaller, thin-fleshed Clitocybe mushrooms that are commonly referred to as hygrophanous.

Clitocybe rivulosa contains a toxin called muscarine, which causes symptoms similar to nerve agent exposure. After eating the mushroom, symptoms such as excessive salivation, sweating, and tearing may occur within 15-30 minutes. With larger doses, symptoms may include abdominal pain, nausea, diarrhea, blurred vision, and difficulty breathing. These symptoms usually go away within two hours. Death is rare, but in severe cases, it can be caused by breathing problems. The specific antidote is atropine.

Other names: Fool's Funnel, False Champignon, Deadly Clitocybe, Sweating Mushroom, German (Feld-Trichterling, Weißer Gifttrichterling), Netherlands (Giftige weidetrechterzwam).

Clitocybe rivulosa Mushroom Identification

1. Cap

   0.79 to 1.57 inches (2 to 4 cm) wide, shallowly convex in youth, expanding to nearly plane with a slightly depressed to umbonate disc; margin incurved, then decurved to occasionally raised in age; surface canescent, white, ashy-gray to grayish-tan; streaked or water-spotted at maturity; context thin, 0.12 to 0.16 inches (3 to 4 mm) thick at the disc, 1-2 mm at the margin; context soft, cream-buff, unchanging; odor mild; taste mild to slightly astringent with time.

2. Gills

   The gills adnate at first, subdecurrent in age, close, cream-buff, becoming tan, relatively narrow; lamellulae in three to four series.

3. Stem

   0.79 to 1.57 inches (2 to 4 cm) long, 0.16 to 0.31 inches (4 to 8 mm) thick, equal to enlarged at the apex, straight or curved, solid in youth, eventually hollow, often flattened in cross section, not leathery or tough; surface appressed fibrillose, pallid, darkening where handled; partial veil absent.

4. Spores

   Spores 4.0-5.0 x 2.0-3.0 µm, smooth, thin-walled, elliptical-oblong in face-view, elliptical and inequilateral in profile, hilar appendage well-developed, inamyloid; spores white in deposit.

5. Spore Зrint

   White.

6. Habitat

   Clitocybe rivulosa grows in grasslands and pastures, forming fairy rings, and it is infrequent to occasionally common. It is widely distributed from summer to autumn in Europe and North America.

Clitocybe rivulosa Look-Alikes

1. Marasmius oreades

   Its cap is uniform in color, ranging from buff to tan, unlike the pale gray and streaked cap of Clitocybe rivulosa. Its gills are more widely spaced, attached to the stem without running down it, and its stem is tough and leathery. Another unique feature of Marasmius oreades is that its fruiting bodies can revive after drying, which is not observed in Clitocybe rivulosa.

2. Calocybe gambosa

   Can be found in similar habitats. It is characterized by thicker cap flesh and has a mealy odor.

Clitocybe rivulosa Taxonomy and Etymology

The mushroom was first called Agaricus rivulosus by Christian Hendrik Persoon in 1801. Later on, a German naturalist named Paul Kummer renamed it to its current name in 1871.

As the cap of the mushroom ages, it can develop circular cracks on its surface, and the name rivulosa refers to this characteristic.

Another similar mushroom called Clitocybe dealbata may be considered as the same species as C. rivulosa, but if they are differentiated, rivulosa is the preferred name for both. The differences between the two are based on their size, gill shape, and the tendency of the margin to crack up.

The name of the mushroom, Clitocybe, means 'sloping head'. The specific name, rivulosa, comes from a Latin word that means channel, river, or stream. It is likely a reference to the faint channels or ridges that form on the mushroom's cap as it matures.

Clitocybe rivulosa Synonyms and Varietes

• Agaricus rivulosus Pers.

• Agaricus rivulosus var. neptuneus Berk. & Broome

• Clitocybe dealbata

• Clitocybe dealbata var. minor Cooke

• Clitocybe dealbata var. rivulosa (Pers.) P. Kumm., 1871

• Clitocybe dealbata var. sudorifica Peck, 1911

• Clitocybe rivulosa var. neptunea (Berk. & Broome) Massee

• Clitocybe subodorifica (Peck) Peck

• Omphalia rivulosa (Persoon) Quélet, 1886

Sources:

Photo 1 - Author: Strobilomyces (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 2 - Author: Andreas Kunze (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 3 - Author: Georgy Vinogradov (Creative Commons Attribution 4.0 International)

Photo 4 - Author: Gailhampshire (Creative Commons Attribution 2.0 Generic)