Tuber sphaerospermum (Malençon) P. Roux, Guy Garcia & M.C. Roux, in Roux, Mille et Un Champignons: 13 (2006)
Ascomata: hypogeous, subglobose, often irregular in form and gibbous, 2-3 cm in size, smooth, initially whitish, becoming ochre
Gleba: firm, solid, initially whitish, becoming dark brown, marbled with white veins.
Odour: faint, no distinctive.
Taste: faint, nutty
Tuber borchii var. sphaerosperma was originally described in sandy pine forests of the Atlantic coast of Morocco (ancient region of Mauritania). They ripen from April to May. Our specimens were found under evergreen oaks, in siliceous soil, in April and May.
Tuber borchii var. sphaerosperma is not accepted by all authors. For some of them it would be synonymous of Tuber puberulum. They are macroscopically identical to Tuber oligospermum and are harvested in the same habitat, in northern Africa. They differ only by peridium structure.
Asci: subglobose to ovate or ellipsoid, sessile, thick walled, 50-75 x 40-55 µm, 1-4 (-5)-spored (usually 3-spored).
Ascospores: 20-32 (-38) µm diam. excluding ornament, size variable depending on number of spores in the ascus, globose, light yellow, ochre at maturity, translucent, ornamented with a regular reticulum with polygonal meshes 4-6 µm high, 5-6 µm long, 4-6 across width of spore.
Peridium: 200-300 µm thick, pseudoparenchymatous the outermost 50-100 µm, composed of subglobose, thick-walled cells, 10-25 µm diam , inner peridium of interwoven hyphae