Truffle Genus: Stephensia

Stephensia sp. ascospore scale = 10 µm

Kingdom: Fungi Phylum: Ascomycota Order: Pezizales Family: Pyronemataceae

Spore Characters

Surface: Smooth.
Shape and Size: Globose to ellipsoid and 12-26 µm in diameter or ellipsoid and 28-40 x 15-18 µm.
Wall: 1-2 layered, 0.5-1 µm thick..
Color in Water: Hyaline.
Melzer's Reaction: Not distinctive.
Comments: The largest globose spores of Stephensia species barely overlap in size the smallest spores of Hydnocystis species. Barssia yezo-montana keys out with either genus as an intermediate in spore characters, but it is rare and known only from Japan.

View photos of Stephensia spores

Sporocarp Characters

Shape and Size: Subglobose to irregular, 1-7 cm in diameter.
Peridium: Brown, tomentose.
Gleba: Solid white to pale brown-yellow, infolded tissue or with chambers lined with non-amyloid asci and loosely stuffed with cottony hyphae.
Odor: Strong, unpleasant.

View photos of Stephensia sporocarps

Name Derivation

Named by French botanist and mycologist Louis René Tulasne (1815-1885) and his younger brother French physician and mycologist Charles Tulasne (1816-1884) (1851) in honor of the English physician and collector of truffle-like fungi, Henry Oxley Stephens (1816-1881).

Distribution

North America, Europe, and West Asia. The genus is infrequent and usually localized.
Season: Summer and autumn.
Species known from North Temperate Forests: Four; one other has been recorded from the Southern Hemisphere.

Keys and Descriptions

Hawker (1954) describes and illustrates the most common species, Stephensia bombycina (Vittadini) Tulasne and Tulasne. The other described species, S. peyronelii Mattarolo (known only from Italy) and S. shanori (Gilkey) Gilkey (known only from Illinois) and S. bynumii (only known from Oregon) are described by Ceruti (1960), Gilkey (1961), Trappe et al. (1997), and Montecchi and Sarasini (2000) respectively. Trappe et al. (1997) provide a key to the species of the genus.