The
fruit body of the fungus is characterized by its purplish-black, semicircular
caps with spines on the cap underside. The caps, which measure up to wide by broad and thick at the base, become tough and woody when dried. The spines on the cap underside are up to 3 mm long, and are densely packed, numbering about 1–3 per millimetre.
Nigrohydnum has a dimitic
hyphal system, containing both generative hyphae with
clamp connections and skeletal hyphae. The
spores of
Nigrohydnum nigrum are cylindrical, thin-walled,
hyaline, and measure 4.5–2
μm. They are
inamyloid. ==Distribution==