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Agrocybe and Cyclocybe  

[ Basidiomycota > Agaricales > Strophariaceae . . . ]

by Michael Kuo

The mushrooms in Agrocybe and Cyclocybe have brown spore prints and are small to medium-sized, saprobic species that grow in grass, wood chips, dung, garden mulch, or in woods—either terrestrially, or from deadwood. They are not subject to rapid decay (in contrast to the mushrooms in Bolbitius), and the caps, with a few exceptions, are dry. Unlike species of Conocybe, which have "cone heads," Agrocybe species have convex to bell-shaped or nearly flat caps.

In my area (central Illinois) May and June are the months for most Agrocybe species, and the little mushrooms proliferate in urban settings and along country roads in ditches and fields. There's no stopping them—but, after the first or second excited Agrocybe stop of the year, my eager slides to meager. The truth is, they're kind of boring, and many of them look very similar.

Field characters used to identify Agrocybe and Cyclocybe species include overall dimensions, the presence or absence of a partial veil (leaving remnants on the edge of the cap, or a ring on the stem), and information about where the mushrooms were growing: in grass, in woodchips, in the woods, or in urban settings.

However, identification in Agrocybe and Cyclocybe often hinges on microscopic examination. Observation of spores—their dimensions, and the size of the pore at one end of the spore, if present—can settle several identification quandaries in this group of mushrooms. Occasionally, observation of cystidia is also important.

Traditionally, Cyclocybe erebia and Cyclocybe cylindracea (AKA cylindrica and aegerita) were treated as species of Agrocybe, since the mushrooms share so many morphological features. But recent research (Vizzini, Angelini & Ercole 2014) demonstrates that erebia and cylindracea are actually not very closely related to Agrocybe species, using phylogenetic species concepts.

 

Agrocybe praecox

Agrocybe pediades

Cyclocybe erebia

Agrocybe praecox



Key to 16 Species of Agrocybe and Cyclocybe in North America



1.Partial veil present, covering the gills in young specimens and later leaving remnants on the cap margin and/or on the stem as a ring or ring zone—or, less often, disappearing entirely by maturity.
2

1.Partial veil absent in all stages of development.
9


2.Cap dark brown in all stages of development; gills running down the stem.

2.Cap paler, at least by maturity; gills attached to the stem or pulling away from it, but not running down it.
3


3.Usually growing in grass; occasionally growing elsewhere.
4

3.Usually growing in woodchips, on soil in gardens or landscaping, or in woods on soil or on wood; occasionally growing in grass.
5


4.Stem 2–4 mm thick; cap honey yellow to dull yellow; veil evidence quickly disappearing; cap surface red or pinkish with KOH.

4.Stem 3–15 mm thick; cap white to creamy yellowish; veil often persisting on cap margin and stem; cap surface negative to yellowish with KOH.


5.Growing in clusters on wood; rare in North America, possibly limited to the Southeastern United States and Mexico; cap brown when young, becoming pale from the margin inward with development; spores with only a small (0.5 µm) germ pore.
Cyclocybe cylindracea

5.Not usually growing in clusters; variously distributed in North America; cap variously colored; spores with a germ pore 1–2 µm wide.
6


6.Appearing almost exclusively in urban settings, usually in woodchips or compost areas, in spring.

6.Appearing in woodland settings.
7


7.Stem 2–4 mm thick; usually growing in marshes and bogs; cheilocystidia mostly clavate.

7.Stem 4–10+ mm thick; growing in various ecosystems, including riverine locations, but not usually in marshes and bogs; cheilocystidia mostly utriform.
8


8.Distributed from the Rocky Mountains westward.

8.Distributed east of the Rocky Mountains.


9.Growing from the deadwood of hardwoods in woodland settings; spores under 9 µm long.

9.Growing in grass, or on woodchips in urban settings; spores variously sized.
10


10.Mature stem 5–20 mm thick.
11

10.Mature stem 2–5 mm thick.
13


11.Fresh cap dry and velvety; pileocystidia present.
Agrocybe putaminum

11.Fresh cap sticky; pileocystidia absent.
12


12.Fresh cap brown to reddish brown; spores 8–11 µm long.
Agrocybe sororia

12.Fresh cap with olive shades; spores 11–13 µm long.
Agrocybe smithii


13.Growing on dung; taste bitter.
Agrocybe amara

13.Growing in grass; taste not bitter.
14


14.Most spores longer than 10.5 µm.
15

14.Most spores shorter than 10.5 µm.
16


15.Widely distributed; KOH red on cap; pleurocystidia absent or very rare.

15.Tropical and subtropical; KOH reaction not recorded; pleurocystidia present.
Agrocybe retigera


16.Odor mealy; spores with a large (1–2 µm) germ pore; pleurocystidia with fingerlike projections.
Agrocybe arvalis

16.Odor not distinctive; pleurocystidia without fingerlike projections; spores with small, inconspicuous germ pore.
Agrocybe vervacti



References

Caciali, G., V. Caroti & F. Doveri (1997). Note su alcune Bolbitiaceae Singer. Rivista di Micologia 2: 109–123.

Calaça, F. J. S., V. G. Cortez & S. Xavier-Santos (2020). Dung fungi from Brazil: Agrocybe pediades (Fr.) Fayod (Basidiomycota) in Cerrado. Scientia Plena 16: 1–6.

Cortez, V. G. & R. M. B. da Silveria (2005). First report of Agrocybe retigera (Speg.) Singer (Bolbitiaceae, Agaricales) from Brazil. Biosciências 13: 227–229.

Flynn, T. & Miller, O. K. Jr. (1990). Biosystematics of Agrocybe molesta and sibling species allied to Agrocybe praecox in North America and Europe. Mycological Research 94: 1103–1110.

González, P. & LaBarere, J. (1998). Sequence and secondary structure of the mitochondrial small-subunit rRNA V4, V6, and V9 domains reveal highly species-specific variations within the genus Agrocybe. Applied and Environmental Microbiology 64: 4149–4160.

Halama, M. (2016). Agrocybe putaminum (Agaricales, Basidiomycota), new for Poland. Polish Botanical Journal 61: 293–299.

Lechner, B. E. (2015). Especies de Agaricales (Basidiomycota) halladas por primera vez en la Argentina: Agrocybe molesta, Coprinopsis romagnesiana y Gymnopus villosipes. Boletín de la Sociedad Argentina de Botánica 50: 303–307.

Malysheva, E. F. & A. A. Kiyashko (2011). Contribution to the study of Agrocybe pediades complex (Agaricales) in Russia based on nrITS sequences. Mycologia Balcanica 8: 115–124.

Nauta, M. M. (2003). A new Agrocybe on woodchips in northwestern Europe. Persoonia 18: 271–274.

Nauta, M. M. (2004). Notulae ad floram agaricinam Neerlandicam--XLIII. Notes on Agrocybe. Persoonia 18: 429–433.

Nauta, M. M. (2005). Agrocybe. In Noordeloos, M. E., Th. W. Kuyper & E. C. Vellinga, eds. Flora Agaricina Neerlandica: Critical monographs on families of agarics and boleti occurring in the Netherlands. Volume 6. Boca Raton: Taylor & Francis. 204–221.

Niveiro, N., M. Uhart & E. Albertó (2020). Revision of the genera Agrocybe and Cyclocybe (Strophariaceae, Agaricales, Basidiomycota) in Argentina. Rodriguésia 71: e02272018.

Ryman, S. (2018). Agrocybe Fayod. In Knudsen, H. & J. Vesterholt, eds. Funga Nordica: Agaricoid, boletoid, clavarioid, cyphelloid and gastroid genera. Copenhagen: Nordsvamp. 928–931.

Singer, R. (1977). Agrocybe. In: Keys for the identification of the species of Agaricales I. Sydowia 30: 194–206.

Uhart, M. & E. Albertó (2007). Morphologic characterization of Agrocybe cylindracea (Basidiomycetes, Agaricales) from America, Europe and Asia. Revista Mexicana de Micología 24: 9–18.

Vizzini, A., C. Angelini & E. Ercole (2014). Le sezioni Velatae e Aporus di Agrocybe sottogenere Aporus: rivalutazione del genere Cyclocybe Velen. ed una nuova specie. Bollettino della Associazione Micologica ed Ecologica Romana 92: 21–38.

Watling, R. (1982). British Fungus Flora, Agarics and Boleti, 3: Bolbitiaceae: Agrocybe, Bolbitius & Conocybe. Edinburgh: Her Majesty's Stationery Office. 139 pp.

Watling, R. & H. E. Bigelow (1983). Observations on the Bolbitiaceae—22. Mycotaxon 17: 377–397.



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Kuo, M. (2021, February). Agrocybe and Cyclocybe. Retrieved from the MushroomExpert.Com Web site: http://www.mushroomexpert.com/agrocybe.html


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