Tricholoma acerbum

A species typical of broadleaf forests, preferring calcareous soils, with a convex to flattened pileus, inrolled margin, 5 to 15 cm in diameter, cream to brownish with reddish tints at the center, adnate cream-white lamellae that become spotted with age, cylindrical stipe concolorous with the pileus, lacking a distinct odor, and with a slightly acrid to bitter taste upon mastication.

Cuticle filamentous, formed by thin-walled hyphae containing brownish pigment inside, densely interwoven, 2.5 to 5 µm wide, septate with simple septa (without clamp connections).

Without cystidia or other sterile elements in the hymenium.

Lamellar trama regular.

Basidia cylindric-clavate, 25 to 30 µm long, 5 to 7 µm wide, with simple base and four sterigmata (4-spored).

Spores ovoid to short-ellipsoid, smooth, hyaline, thin-walled, with an eccentric apiculus at one end, 4.5 to 6 µm long, 3.5 to 4.5 µm wide, containing a large oil droplet inside occupying much of the total volume, inamyloid in Melzer's reagent.