- A family or subgroup genus of the fungi of which Boletus edulis or cep is the most well known. All varieties are characterized by close-packed tubular structures under the cap in place of the more common gills and only one variety, the bitter boletus, is poisonous and is distinguished from the cep by its bitter taste. Of the others, the white boletus, B. albidus, the devil’s boletus, B. satanus, the red-stalked boletus, B. erthropus, and the yellow boletus, B. calopus, are inedible. All the other 23 varieties are edible. However all pickers should be trained by an expert.