Truffle Genus: Hymenogaster

Hymenogaster boozeri basidiospore scale = 15µm

Kingdom: Fungi Phylum: Basidiomycota Order: Agaricales Family: Strophariaceae

Spore Characters

Surface: Wrinkled to irregularly ridged or ornamented with warts or pegs.
Shape and Size: Symmetrical, ellipsoid to ovoid, obovoid, fusoid, citriform, or subcylindrical with an obscure to prominent apical hump, 9-35 (-40) x 4.5-18 µm (including ornamentation); sterigmal attachment usually broad.
Wall: Mostly single layer 0.5-1 µm thick beneath the ornamentation; apical projection, when present, thin-walled.
Color in Water: Pale yellow-brown to dark brown from the pigmented ornamentation; the apical projection, when present, is pale brown to hyaline.
Melzer's Reaction: Not distinctive.
Comments: Related in spore and sporocarp characters to the mushroom genus Hebeloma (Peintner et al., 2001). Its apical hump distinguishes it from the genus Protoglossum, which is related to the mushroom genus Cortinarius.

View photos of Hymenogaster spores

Sporocarp Characters

Shape and Size: Subglobose to globose or irregular, 0.4-50 mm broad.
Peridium: White to yellow or black-brown, in some species staining lilac to dark brown where bruised or exposed, smooth or felty or wrinkled, often thin and fragile.
Gleba: Cinnamon; basal pad sometimes present and columella somteimes prominent, cylindrical to dendroid.
Odor: Not distinctive to strongly farinaceous, of green corn, cheesy, or of pine pitch.

View photos of Hymenogaster sporocarps

Name Derivation

Named by Italian obstretrician and mycologist (1800-1865) Carlo Vittadini (1831) from Greek, hymeno- (membrane or thin skin) and -gaster (literally meaning "stomach", but in mycological usage referring to Gasteromycetes, i.e. the puffballs), hence "thin-skinned puffball."

Distribution

Beneath ectomycorrhizal shrubs and trees in the Northern Hemisphere.
Season: Individual species may be strongly seasonal, others fruit throughout the year. In the Pacific Northwest, Hymenogaster subalpinus is the most common hypogeous fungus in winter.
Species known from North Temperate Forests: About 50 described species seem to be valid, although the genus needs critical revision. Some Southern Hemisphere species have been introduced to the Northern Hemisphere as "hitchhikers" on roots of imported Eucalyptus seedlings.

Keys and Descriptions

The most complete work on Hymenogaster (Dodge and Zeller, 1934) needs revision. Less inclusive keys and descriptions are found in Smith (1966) and Fogel (1985) for North America and Soehner (1962) and Gross et al. (1980) cover most European species. With the present state of knowledge, attempts to identify species more often than not result in frustration. Montecchi and Sarasini (2000).