Hygrocybe is agenus ofagarics (gilled fungi) in thefamilyHygrophoraceae. Calledwaxcaps in English (sometimeswaxy caps in North America),basidiocarps (fruit bodies) are often brightly coloured and have dry to waxycaps, whitespores, and smooth, ringlessstems. In Europe they are characteristic of old, unimproved grasslands (termedwaxcap grasslands) which are a declining habitat, making manyHygrocybe species ofconservation concern. Four of these waxcap-grassland species,Hygrocybe citrinovirens,H. punicea,H. spadicea, andH. splendidissima, are assessed as globally "vulnerable" on theIUCN Red List of Threatened Species.^[2] Elsewhere waxcaps are more typically found in woodlands. Most are ground-dwelling and all are believed to bebiotrophs. Around 150 species are recognized worldwide. Fruit bodies of severalHygrocybe species are considerededible and are sometimes offered for sale in local markets.

Hygrocybe
Hygrocybe cantharellus
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Basidiomycota
Class:	Agaricomycetes
Order:	Agaricales
Family:	Hygrophoraceae
Genus:	Hygrocybe (Fr.)P.Kumm. (1871)
Type species
Hygrocybe conica (Schaeff.) P.Kumm. (1871)
Synonyms[1]
GodfriniaMaire (1902) BertrandiaR.Heim (1936) Pseudohygrocybe(Bon) Kovalenko (1988)

Hygrocybe was first published in 1821 by Swedish mycologistElias Magnus Fries as a subsection ofAgaricus and in 1871 was raised to the rank of genus byKummer. In several papers,Karsten andMurrill used the nameHydrocybe, but this is now taken as an orthographic variant ofHygrocybe. The generic name is derived from theGreek ῦγρὁς (= moist) + κυβη (= head).^[3][4]

Despite its comparatively early publication, the genusHygrocybe was not widely accepted until the 1970s, most previous authors treating it as a synonym ofHygrophorus, a related genus ofectomycorrhizal agarics.^[3][5]

Recentmolecular research, based oncladistic analysis ofDNA sequences, has shown thatHygrocybesensu lato isparaphyletic and does not form a singleclade within the Hygrophoraceae. As a result, many species formerly referred toHygrocybe have been transferred to the generaChromosera,Cuphophyllus,Gliophorus,Gloioxanthomyces,Humidicutis,Neohygrocybe, orPorpolomopsis.^[6][7][8][9] This leavesHygrocybesensu stricto as a smaller but more cohesive genus of species related to thetype,Hygrocybe conica.

No comprehensivemonograph of the genus has yet been published. InEurope, however, species ofHygrocybe have been illustrated and described in a standard English-language guide by Boertmann (2010)^[10] and also (together withHygrophorus) in an Italian guide by Candusso (1997).^[11] European species have also been covered, more briefly, in descriptive French keys by Bon (1990).^[12] Dutch species were illustrated and described by Arnolds (1990).^[13] No equivalent modern guides have been published forNorth America, the most recent being byHesler &Smith (1963).^[5] There is, however, a guide to Californian species by Largent (1985).^[14] InAustralia,Hygrocybe species have been illustrated and described by Young (2005)^[15] and inNew Zealand by Horak (1990).^[16]

•  
  Hygrocybe flavescens
•  
  Hygrocybe conica
•  
  H. chlorophana
•  
  H. appalachianensis

Fruit bodies ofHygrocybe species are allagaricoid, most (but not all) having smooth to slightly scaly caps that are convex to conical and dry to waxy or viscid when damp. Many (but not all) are brightly coloured in shades of red, orange, or yellow. Where present, the gills beneath the cap are often equally coloured and usually distant, thick, and waxy. One atypical South American species,Hygrocybe aphylla, lacks gills.^[17] The stems ofHygrocybe species lack aring. Thespore print is white. Fruit bodies of some species, notablyHygrocybe conica, blacken with age or when bruised. Microscopically,Hygrocybe species lack truecystidia and have comparatively large, smooth,inamyloidbasidiospores.^[10]

Species ofHygrocybe are soil-dwelling. In Europe, most species are typical of unimproved (nutrient-poor), short-sward grasslands, often termed "waxcap grasslands",^[18] but elsewhere they are more commonly found in woodland.

Their metabolism has long been debated, but recent research suggests that they are notsaprotrophic^[19][20] but rathersymbiotically associated with the roots of higher plants or mosses. Hyphae ofH. conica have been detected in plant roots.^[20]

Species are distributed worldwide, from the tropics to the sub-polar regions. Around 150 have been described to date.^[21] Waxcaps receive most attention in northern Europe,^[22] where they are found in nutrient-poor pastures.^[10] However, outside Europe, waxcaps are more commonly associated with woodland habitats, for example the sclerophyll forests site atLane Cove Bushland Park andFerndale Park,Sydney.^[23]

In Europe, waxcap grasslands and their associated fungi are of conservation concern, since unimproved grasslands (formerly commonplace) have declined dramatically as a result of changes in agricultural practice. This decline has led to four EuropeanHygrocybe species,Hygrocybe citrinovirens,H. punicea,H. spadicea, andH. splendidissima, being assessed as globally "vulnerable" on theIUCN Red List of Threatened Species.^[2]

Elsewhere, several rare and localized endemic species are assessed as globally "endangered" on the IUCN Red List of Threatened Species.^[2] They includeHygrocybe boothii in Australia,Hygrocybe noelokelani andHygrocybe pakelo in Hawaii,Hygrocybe striatella in Chile, andHygrocybe flavifolia in California.

BecauseHygrocybe species cannot be maintained inculture,^[24] none is cultivated commercially. Fruit bodies of a few species are considered edible in eastern Europe, south-east Asia, and Central America and are collected and consumed locally.^[25]

• WaxCap Website,University of Wales, Aberystwyth