The cortex of the large brain contains in its 4th layer (lamina IV) a thin, to the naked eye invisible, layer of longitudinal myelinated nerve fibers (the outer layer of Baillarger). Within the primary visual cortex (area 17), this layer is heavily thickened and just visible to the naked eye as a white line or streak. This streak is called after its discoverer (1700s) Stria Gennari.
The primary visual cortex, in turn, is therefore often called Area striata.