Collybia cookei

Description

Collybia cookei is a species of fungus in the family Tricholomataceae, and one of three species in the genus Collybia. It can be distinguished by its small dingy white mycenoid stature and growth from small pumpkin-colored sclerotia buried in humus, very rotten wood, or on the blackened remains of other fungi. If the sclerotia are not seen, the species is indistinguishable from Collybia cirrhata. In California, there occur two other sclerotium-forming collybias, Collybia tuberosa and Dendrocollybia racemosa.

It is known in Europe, Asia, and North America. The edibility of the mushroom has not been determined.

Common names: Splitpea Shanklet.

Mushroom Identification

1. Ecology

   Saprobic; growing gregariously on the remains of decayed mushrooms or humus (occasionally on well-rotted wood); found under hardwoods or conifers; summer and fall; fairly widely distributed in North America.

2. Cap

   2-9 mm; convex with a somewhat inrolled margin when young, becoming broadly convex to flat, with or without a shallow central depression; dry or moist; more or less bald; whitish to buff, sometimes with a darker central area.

3. Gills

   Attached to the stem; close or almost distant; whitish.

4. Stem

   1-6 cm long; 1-2 mm thick; more or less equal; dry; whitish; becoming hollow; attached to sclerotia which are more or less round, yellowish to orangish-yellow, and measure 4-10 mm.

5. Flesh

   Whitish; thin.

6. Spore Print

   White.

7. Microscopic Features

   Spores 4.5-6 x 3-3.5 µ; smooth; ellipsoid or sublacrymoid; inamyloid. Pleuro- and cheilocystidia absent. Pileipellis a cutis or ixocutis of cylindric elements 3.5-7 µ wide; with scattered, rare pileocystidia.

Look-Alikes

1. Collybia tuberosa

   Differs in forming ellipsoid, dark reddish-brown to almost black sclerotia and typically develops from old, rotten mushrooms.

2. Dendrocollybia racemosa

   Differs in forming a stipe covered with short side branches topped with asexual spores.

3. Asterophora lycoperdoides

   Is distinct from C. cookei because of the powdery brown asexual spores (chlamydospores) produced on the cap surface.

History

The species was first described in the scientific literature in 1928 as Collybia cirrhata var. cookei by the Italian mycologist Giacomo Bresadola. In a 1935 publication, Jean D. Arnold reported a series of cultural studies with monokaryon isolates (hypha having only a single haploid nucleus) of several Collybia species to determine their mating type. All attempts to produce hybrids between C. cirrhata var. cookei and C. cirrata or mycelial fusions between the two species failed. This sexual incompatibility indicated that the two taxa were separate species, and she raised the taxon from varietal to specific status, calling it Collybia cookei.

The species has also been called Microcollybia cookei in a 1979 publication by Joanne Lennox, but the genus Microcollybia has since been folded into Collybia. Marcel Bon and Régis Courtecuisse considered the species a variety of Collybia tuberosa in a 1988 publication. A 2001 molecular analysis based on the ribosomal DNA sequences confirmed that C. cookei is phylogenetically related to C. tuberosa and C. cirrhata, and that the three species form a monophyletic group that comprise the genus Collybia.

The specific epithet cookei honors the British mycologist Mordecai Cubitt Cooke.

Synonyms

1. Collybia cirrhata var. cookei Bres. (1928)

2. Microcollybia cookei (Bres.) Lennox (1979)

3. Collybia tuberosa var. cookei (Bres.) Bon & Courtec. (1987)

Photo sources:

Photo 1 - Author: alan_rockefeller (Attribution-ShareAlike 4.0 International)

Photo 2 - Author: wearethechampignons (Public Domain)