Bolbitius titubans

Description
Mushroom Identification
Look-Alikes
History
Synonyms

Description

Bolbitius titubans is a widespread nonpoisonous species of mushroom found in America and Europe. It is a small, yellow, attractive fungus that is easily recognized by its viscid, striate cap, yellow-brown gills, rust-brown spores, and lack of a ring. It grows chiefly on dung or heavily fertilized soil, and sometimes on grass.

Like many small Coprinus (s.l.) species, fruitings are ephemeral, mushrooms opening in the morning, then shriveling by the end of the day. Occasionally, unusually robust specimens are found which may persist for several days.

Common names: Yellow Fieldcap, Dooiergele mestzwam (Netherlands), Goldmistpilz (German), Slzečník žloutkový (Czech Republic).

Mushroom Identification

Cap

1.5-5 cm; egg-shaped or nearly round when young, expanding to broadly bell-shaped or broadly convex, and eventually flat with a depressed central bump; fragile; slimy when fresh; yellow or greenish-yellow (sometimes brownish or grayish), often fading to grayish or pale tan but (usually) retaining a yellowish center; smooth; usually strongly lined by maturity, often nearly all the way to the center. Specimens developing a pocketed or veined cap surface as the slime dries out are not infrequent. Young specimens sometimes display a felty, whitish cap margin, but this appears to be the result of contact with the stem (which also features the feltiness) in the button stage, rather than remnants of a true partial veil.
Gills

Free from the stem or narrowly attached to it; close; fragile and soft; whitish or pale yellowish, becoming rusty cinnamon; often gelatinizing somewhat in wet weather.
Stem

3-12 cm long; up to nearly 1 cm thick; equal or tapering to the apex; hollow; fragile; finely scaly, powdery, or finely hairy--or more or less smooth; white with a yellowish apex and/or base, or yellowish overall.
Flesh

Insubstantial; yellowish.
Odor and Taste

Not distinctive.
Chemical Reactions

KOH on cap surface negative to dark gray.
Spore Print

Rusty brown.
Habitat

Saprobic, growing alone, scattered, or gregariously on dung and in fertilized grass; summer and fall (and winter in warm climates); widely distributed in North America.
Microscopic Features

Spores 10-16 x 6-9 µ; more or less elliptical, with a truncated end; smooth; with a pore. Brachybasidioles and cheilocystidia are present. Basidia abruptly clavate. Pileipellis a hymeniform trichoderm.

Look-Alikes

Leucocoprinus birnbaumii

A tropical species in the Bay Area occurs mostly in greenhouses, is similar in size and cap color but the cap is not viscid, the gills are free, there is a ring, and the spores are white.
Pluteus chrysophaeus

The spores are pink rather than cinnamon brown. Grows on wood rather than on grass.
Bolbitius expansus

Has a yellow stem and a grayish yellow cap that lacks a retained yellowish center at maturity.
Bolbitius variicolor

Has a dusky olive cap and a scaly yellow stem.
Conocybe siliginea

Differ only slightly in size, shape, and color. However, experienced mushroom observers notice small differences right away. Paler to brownish caps without yellow tones, only a fine ridge in old age, mucusless caps, brownish stems, and different micro-characteristics separate this mushroom from the B. titubans.

History

In 1789 French mycologist, Jean Baptiste Francois Pierre Bulliard described this species and named it Agaricus titubans. In 1838 Swedish mycologist Elias Magnus Fries renamed it Bolbitius titubans.

The genus name Bolbitius means "of cow dung". The specific epithet titubans means staggering or wavering.