Mealy tooth

The fruit bodies of Hydnellum ferrugineum are more or less top-shaped with caps that are 3–10 cm (1.2–3.9 in) in diameter. They are at first convex, then pulvinate (cushion-shaped), later flattening or becoming slightly depressed in the center. The cap surface of young fruit bodies is uneven, with a velvety to felted texture, and a whitish to pink color. It sometimes exudes blood-red drops of fluid in the depressions. The surface later becomes flesh-colored to dark reddish brown, but with wavy margin remaining whitish. The lower surface of the fruit body bears the hymenium, the fertile spore-bearing tissue. It comprises a dense arrangement of white to reddish brown spines up to 6 mm long, hanging vertically downwards. The stout stipe measures 1–6 cm (0.4–2.4 in) long by 1–3 cm (0.4–1.2 in) thick, and is the same color as the cap. Fruit bodies have a "distinctly mealy" odor (similar to the smell of freshly ground flour), but are inedible. The flesh is reddish or purplish-brown with white flecks. Initially spongy and soft, it becomes tough and corky as the fruit body matures. In the stipe, the flesh can become blackish in age. Like other Hydnellum species, fruit body tissue is made of generative hyphae that do not expand. This slows the growth of the fruit body, often enabling it to persist for several months. The fungus employs an indeterminate growth pattern, in which the fruit body formation begins from a vertical column of hyphae that eventually expand at the top to form the cap. Any solid objects encountered during growth, such as grass or twigs, can be enveloped by the expanding fruit body. Similarly, closely neighboring caps can fuse together during growth. The broadly ellipsoid to roughly spherical spores are 5.5–7.5 by 4.5–5.5 μm. Their surfaces are covered with small rounded bumps. The basidia (spore-bearing cells) are narrowly club-shaped, four-spored, and measure 25–30 by 6–7.5 μm. The hyphae of the flesh are brownish with thin walls, and measure 4–6 μm; hyphae in the spines are thin-walled, septate, and sometimes branched, measuring 3.5–4.5 μm. The hyphae do not have clamp connections.