Tuber rhenanum Fuckel (1869), Jahrbücher des Nassauischen Vereins für Naturkunde 23 u. 24: 247
Ascomata: hypogeous, subglobose or irregular in form and lobed, 1-5 cm in size, warted, reddish brown to blackish. Warts 0,5-2 mm across, polygonal, irregular in form and size, flattened, ridged.
Gleba: firm, solid, brown purplish to black at maturity, marbled with numerous, wide, white, meandering veins.
Odour: strong, pleasant, garlicky, likeTuber magnatum
Taste: strong, pleasant, garlicky, likeTuber magnatum
Tuber macrosporum usually grows in limestones soils and often in clay soils. In Italy, you can find these truffles in the same places as Tuber magnatum. They are associated with the roots of several trees: poplars (Populus), willows (Salix), hazels (Corylus), oaks(Quercus) and lindens (Tilia).
Tuber macrosporum is easily recognizable by the large spores and the low and flattened warts. That truffle sometimes looks almost smooth and receives the popular name of “smooth black truffle”. The first description of this species was probably Tuber cibarium subcinereum alliaceum Bulliard (1791), Histoire Champignons France 74
Tuber macrosporum is is an edible truffle, gastronomically excellent.
Asci: subglobose to ellipsoid, short-stalked, 90-130 x 65-80 µm, 1-3 (-4)-spored (usually 3-spored).
Ascospores: 42-85 x 30-42 (-42) µm excluding ornament, size variable depending on number of spores in the ascus, Q range = 1,40-2,08, ellipsoid, light yellow, brown-reddish at maturity, opaque at maturity, ornamented with a small-meshed reticulum. Meshes polygonal, irregular in form and size, 3-5 (6) µm high, 4-10 µm long, 6-10 across width of spore.
Peridium:150-300 µm thick, composed of agglutinated, interwoven, thick-walled hyphae, brown- reddish in the outermost layers, yellowish in the innermost layers.