sentences:  The cork oak in particular is an important symbiont, and the distribution of "B. aereus" aligns with the tree across Europe and North Africa.The ectomycorrhizae that "B. aereus" forms with sweet chestnut ("Castanea sativa") and downy oak ("Quercus pubescens") have been described in detail.They are characterized by a lack of hyphal clamps, a plectenchymatous mantle (made of parallel-orientated hyphae with little branching or overlap), and rhizomorphs with differentiated hyphae.