Truffle Genus: Radiigera

Radiigera atrogleba basidiospore

Kingdom: Fungi Phylum: Basidiomycota Order: Geastrales Family: Geastraceae

Spore Characters

Surface: Minute coarse warts.
Shape and Size: Globose to broadly ellipsoid, 2.5-6.5 µm in diameter (including ornamentation); attachment not evident or sometimes prominent as a scar, straight.
Wall: Single, thin.
Color in Water: Nearly hyaline to brown.
Melzer's Reaction: Not distinctive.

View photos of Radiigera spores

Sporocarp Characters

Shape and Size: Subglobose to globose with indented basal attachment, 2-8 cm broad.
Peridium: White to pale brown, often staining pink to olive where exposed, bruised, or cut, 3-8 mm thick. With a thin, felty outer layer over a thick, crisp-fleshy layer; some species have a thin, third innermost membrane.
Gleba: White in youth, with a prominent, soft, capitate, white columella, from which straight hyphae radiate to connect with the peridium. The gleba becomes pale brown to black from maturation of the pigmented spores, which at full maturity form a powdery mass.
Odor: Usually mushroom-like or not distinctive, sometimes metallic-disagreeable at maturity.
Comments: Related to the puffball genus Geastrum in the family Geastraceae but remaining closed and below ground. Radiigera and its close relative Pyrenogaster have the smallest ornamented spores of all truffle-like fungi. The two differ primarily in the arrangement of spore-bearing tissue of the gleba. These genera do not separate out from small-spored Schenella species in the key.

View photos of Radiigera sporocarps

Name Derivation

Named by distinguished Oregon mycologist and plant pathologist, Sanford Zeller (1884-1948) (1944) from Latin radii- (radii) and the suffix -ger (bearing), hence "bearing radii" in reference to the straight glebal hyphae that radiate strikingly from the columella of the sporocarp to its peridium.

Distribution

Western United States, at low to mid-level elevations, and northern Europe; associated with species of Populus, Quercus, and the Pinaceae; also two species are known from Australasia and one other from South America.
Season: Spring, summer, or early autumn.
Species known from North Temperate Forests: Four.

Keys and Descriptions

Zeller (1944) initially described three North American species, then added a fourth (Zeller, 1948). Kers (1976) reported the European finds. Toledo and Castellano (1996) present a modern treatment of all species.