The surface of the cerebellum is particularly strongly folded, forming a system of thin, flat and tightly packed transverse/transverse folds - folia cerebelli - separated from each other by narrow and very deep fracture bindings.
Thus, folia cerebelli are arranged perpendicular to the longitudinal axis of the brain. A cross section through a cerebellar blade thus runs parallel to the brain's longitudinal axis and is a sagittal section!! This is important for understanding how Purkinje cells' voluminous, but from the sides flattened, disc-like dendrite trees are arranged parallel to the sagittal plane, forming densely packed transverse rows.
The parallel filaments of the granular cells run transversely in the longitudinal direction of the cerebellar leaf and will thus travel perpendicularly through the dendrite tree of the Purkinje cells.