Tuber microspermum

A species of Truffles

Fruit bodies of Tuber microspermum are yellow-brown, roughly spherical, and measure up to 1.5 cm (0.6 in) in diameter. The surface of the peridium (outer skin) is either smooth, or has minute wart-like projections. The peridium comprises two distinct layers of tissue. The 80–120 μm-thick outer layer is made of somewhat angular to roughly spherical cells that are typically 7.5–12.5 μm in diameter. These cells have thick walls that contain a brown pigmentation. The inner tissue layer of the peridium consists of interwoven hyaline (translucent), thin-walled hyphae measuring 2.5–5 μm wide. The internal spore-bearing tissue (gleba) of the truffle is brown when it is mature. It features white to yellowish-white narrow veins that give it a "marbled" appearance. The truffle has thick-walled asci that have a somewhat spherical, elliptical, or somewhat irregular shape. These asci are usually on a short stalk, contain between one and five spores, and measure 45–70 by 40–60 μm. The spores are elliptical, and dark brown in mature specimens. The size of the spores is typically 15–25 by 12.5–20 μm, although spores from single-spored asci are larger, measuring 30–35 by 22.5–25 μm. Spores have a network pattern (reticulation) and discrete spines on their surface that are usually 4–6 μm long.