Butyriboletus regius

Cuticle filamentous, formed of hyphae interwoven with each other, with intracellular pigment and septa devoid of clamp connections (simple septa).

Cystidia fusiform, ventricose, with attenuated, rounded tips.

Basidia clavate and 4-spored.

Spores cylindrical to slightly fusiform, pale yellow under the microscope, thick-walled, with a lateral apiculus and oil droplets inside.