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Inocybe cookei, commonly known as the straw fibrecap, is a species of mushroom in the Inocybaceae family. It was first described in 1892 by Giacomo Bresadola, and is named in honour of Mordecai Cubitt Cooke. The species can be found in Europe, Asia and North America. It produces small mushrooms of an ochre colour, with a prominent umbo, fibres on the cap and a distinctive bulb at the base of the stem. It grows from soil in mixed woodland, and is encountered in summer and autumn, though is not common. Ecologically, it feeds through use of ectomycorrhiza. Inocybe cookei has been described as both toxic and non-toxic, but either way, is not advised for consumption.

Inocybe cookei
Four light yellow mushrooms growing from dark soil. One has been pulled from the Earth, and lies on its side.
Scientific classification
I. cookei
Binomial name
Inocybe cookei

Inocybe kuthanii Stangl & J.Veselský
Inocybe cookei var. kuthanii (Stangl & J.Veselský) Kuyper

Inocybe cookei
View the Mycomorphbox template that generates the following list
Mycological characteristics
gills on hymenium
cap is campanulate
hymenium is adnexed
stipe is bare
spore print is brown
ecology is mycorrhizal
edibility: poisonous


Taxonomy and namingEdit

I. maculata f. fulva

I. maculata

I. cookei

I. quietiodor

I. rhodiola

I. adaequata

I. erubescens

Phylogeny and relationships of I. cookei and related species in section Maculata based on ITS, large-subunit, and mitochondrial small-subunit rRNA sequence data.[2]

Inocybe cookei was first described by Giacomo Bresadola in 1892;[1] the specific epithet cookei honours the British mycologist Mordecai Cubitt Cooke.[3] Mycologists J. Stangl and J. Veselský described Inocybe kuthanii in 1979,[4] which was later described as a variety of Inocybe cookei (Inocybe cookei var. kuthanii) by Thom Kuyper in 1986,[5] but MycoBank now lists both names as synonyms of I. cookei.[1] The mushroom is commonly known as the straw fibrecap.[6]

Within Inocybe, it is placed within the subgenus Inosperma,[2] and was previously categorised within the section Rimosae.[7] However, phylogenetic analysis has shown that section Rimosae as formerly defined does not form a monophyletic group (that is, descended from a single exclusive ancestor), and former Rimosae species are better grouped into two clades, Maculata and Rimosae. Phylogenetic analysis has placed the species in the clade Maculata. Other species joining I. cookei in the Maculata clade include I. maculata, I. quietiodor, I. rhodiola, I. adaequata, and I. erubescens.[2]


Inocybe cookei has a conical or bell-shaped cap of between 2 and 5 centimetres (0.79 and 1.97 in) in diameter. As the mushrooms age, the cap becomes flatter, and an umbo becomes prominent. The margin of the cap frequently cracks towards the centre. The cap is an ochre colour, and the upper surface is covered in long fibres.[8] The silky fibres thickly cover the cap, starting and the centre and extending to the cap's margin.[9] The species has a whitish or ochre stem of 30 to 60 millimetres (1.2 to 2.4 in) in height by 4 to 8 millimetres (0.16 to 0.31 in) in thickness.[8] There is a distinctive marginate bulb at the base of the stem,[10] and no ring.[9] The flesh is white, becoming yellow with age.[9] Inocybe cookei mushrooms have closely packed adnexed gills (gills that are attached to the stem only on part of their depth).[8][11] Gills on young mushrooms are whitish, then become a grey-tinged pale ochre before becoming cinnamon yellow.[9]

Microscopic featuresEdit

Inocybe cookei leaves a snuff-brown spore print. The spores themselves are bean-shaped,[8] measuring from 5.5 to 10 micrometres (0.00022 to 0.00039 in) by 4 to 6 micrometres (0.00016 to 0.00024 in). The walls of the spores (which are around 0.5 micrometres (2.0×10−5 in) thick) can be smooth or slightly wrinkled, and there is a distinct depression just above the hilum (the scar where the spore was once attached to the basidium).[7] The basidia are four-spored, and the thin-walled, gill-edge cheilocystidia are pear-shaped.[9]

Similar speciesEdit

I. praetervisa (left) and I. rimosa (right) are lookalikes.

The species can be differentiated from the similar I. praetervisa by its spores; the latter "has irregular, lumpy spores".[10] Inocybe rimosa, the split fibrecap, is also similar in appearance; the rarer I. cookei can be differentiated by the smell of honey and the marginate bulb.[6] The colouration, as well as the thick stem with a bulb, are features shared by two other species of Inocybe; I. mixtilis and I. cryptocystis.[12] Another fragrant Inocybe is I. pyriodora, which has an odor resembling cinnamon, or ripe pears in mature specimens; unlike I. cookei, it lacks a bulb at the base of its stem, and bruises a reddish colour when handled or with age.[13]

Distribution and habitatEdit

Inocybe cookei is an occasional to frequent mushroom, found growing in mixed woodland on the ground.[8][10] It is ectomycorrhizal,[14] and grows from summer to late autumn,[8] solitarily or in "trooping groups".[9] It has been recorded in Europe,[8] Russia,[15] China,[16] Mexico,[14] and the United States.[17]

Toxicity and edibilityEdit

Inocybe cookei has been described as both poisonous (due to the presence of muscarine compounds)[10] and non-toxic.[11] Consumption of mushrooms containing muscarine compounds could lead to a number of physiological effects, including: excess salivation, lacrimation, uncontrolled urination or defecation, gastrointestinal problems and emesis (vomiting); this array of symptoms may also be known by the acronym SLUDGE.[18] Other potential effects include a drop in blood pressure, sweating and death due to respiratory failure.[18] The flesh of the mushroom has a mild taste and a slight smell of honey.[6][8] Regardless of its actual toxicity or edibility, it is considered "best avoided".[11]

See alsoEdit


  1. ^ a b c "Inocybe cookei". MycoBank. International Mycological Association. Retrieved 2010-12-23.
  2. ^ a b c Larsson, E.; Ryberg, M.; Moreau, P.-A.; Mathiesen, Å. Delcuse; Jacobsson, S. (2009). "Taxonomy and evolutionary relationships within species of section Rimosae (Inocybe) based on ITS, LSU and mtSSU sequence data" (PDF). Persoonia. 23: 86–98. doi:10.3767/003158509X475913.
  3. ^ Rea, Carleton (1922). British Basidiomycetaceae: a Handbook to the Larger British Fungi. Cambridge, UK: Cambridge University Press. p. 205.
  4. ^ Stangl, J.; Veselský, J. (1979). "Inocybe kuthanii sp. nov. Eine neue Art in Sektion Rimosae, Stirps Cookei Heim gehörend. (Beiträge zur Kenntnis seltenerer Inocyben. Nr. 15)". Ceská Mykologie (in German). 33 (3): 134–37.
  5. ^ Kuyper, T.W. (1986). "A revision of the genus Inocybe in Europe. I. Subgenus Inosperma and the smooth-spored species of subgenus Inocybe". Persoonia Supplement. 3: 51.
  6. ^ a b c Sterry, Paul; Hughes, Barry (2009). Complete Guide to British Mushrooms & Toadstools. HarperCollins. p. 192. ISBN 978-0-00-723224-6.
  7. ^ a b Pegler, D.N.; Young, T.W.K. (1972). "Basidiospore form in the British species of Inocybe". Kew Bulletin. 26 (3): 499–537. doi:10.2307/4120316.
  8. ^ a b c d e f g h Phillips, Roger (1981). Mushrooms and Other Fungi of Great Britain and Europe. London: Pan Books. p. 149. ISBN 0-330-26441-9.
  9. ^ a b c d e f Jordan, Michael (2004). The Encyclopedia of Fungi of Britain and Europe. Frances Lincoln. p. 287. ISBN 978-0-7112-2378-3.
  10. ^ a b c d Kibby, Geoffrey (2003). Mushrooms and Toadstools of Britain and Northern Europe. Hamlyn. p. 99. ISBN 978-0-7537-1865-0.
  11. ^ a b c Pegler, David N. (1983). Mushrooms and Toadstools. London: Mitchell Beazley Publishing. p. 85. ISBN 0-85533-500-9.
  12. ^ Esteve-Raventós, Fernando (2001). "Two new species of Inocybe (Cortinariales) from Spain, with a comparative type study of some related taxa". Mycological Research. 105 (9): 1137–43. doi:10.1016/s0953-7562(08)61978-4.
  13. ^ Arora, D. (1986). Mushrooms Demystified: a Comprehensive Guide to the Fleshy Fungi. Berkeley, California: Ten Speed Press. p. 459. ISBN 0-89815-169-4.
  14. ^ a b Reverchon, Frédérique; Ortega-Larrocea, María d.P.; Pérez-Moreno, Jesús; Peña-Ramírez, Víctor M.; Siebe, Christina (2010). "Changes in community structure of ectomycorrhizal fungi associated with Pinus montezumae across a volcanic soil chronosequence at Sierra Chichinautzin, Mexico". Canadian Journal of Forest Research. 40 (6): 1165–74. doi:10.1139/X10-062.
  15. ^ Peintner, U; Horak, E. (2002). "Inocybe (Basidiomycota, Agaricales) from Kamchatka (Siberia, Russia): taxonomy and ecology". Sydowia. 54 (2): 198–241.
  16. ^ Bi, Zhishu; Zheng, Guoyang; Li, Taihui (1993). The Macrofungus Flora of China's Guangdong Province. Chinese University Press. p. 428. ISBN 978-962-201-556-2.
  17. ^ Kauffman, C.H. (1917). "Tennessee and Kentucky Fungi". Mycologia. 9 (3): 159–66. doi:10.2307/3753332. ISSN 0027-5514. JSTOR 3753332.
  18. ^ a b Hall, Ian Robert; Buchanan, Peter K.; Stephenson, Steven L.; Yun, Wang; Cole, Anthony L.J. (2003). Edible and Poisonous Mushrooms of the World. Timber Press. pp. 108–109. ISBN 978-0-88192-586-9.