A row unit of a row crop harvester head, the row unit having first and second gathering chains (32, 34) and first and second stripper plates (40, 42), the first and second stripper plats (40, 42) laterally spaced to define a slot therebetween, the slot having a width and defining a longitudinal path of travel along which crop stalks pass as the row unit moves forwardly through a field harvesting the row crop, wherein the first gathering chain defines a first continuous loop adapted to rotate, forwardly to rearwardly, above the first stripper plate along a first side of the slot; wherein the second gathering chain defines a second continuous loop adapted to rotate, forwardly to rearwardly, above the second stripper plate along a second side of the slot; a plurality of lateral extensions attached to each of the first and second gathering chains (30, 32) creating respective first and second gathering chain assemblies, characterized by: the plurality of lateral extensions comprising a plurality of individual bristle blocks, each individual bristle block having a base, the base having bristles extending laterally outward from a front side of the base, a back side of the base removably, yet rigidly attaching to the respective first and second gathering chains (32, 34); whereby the bristles of the plurality of bristle blocks of the first gathering chain assembly provide a first substantially continuous conveying surface above and along the first side of the slot; and whereby bristles of the plurality of bristle blocks of the second gathering chain assembly provide a second substantially continuous conveying surface above and along the second side of the slot; and whereby the first and second substantially continuous conveying surfaces extend substantially across the width of the slot such that as the stalks of the row crop are pulled through the conveying surfaces, the bristles capture and prevent loose kernels of the row crop being harvested from falling through the slot. wherein the first gathering chain defines a first continuous loop adapted to rotate, forwardly to rearwardly, above the first stripper plate along a first side of the slot; wherein the second gathering chain defines a second continuous loop adapted to rotate, forwardly to rearwardly, above the second stripper plate along a second side of the slot; a plurality of lateral extensions attached to each of the first and second gathering chains (30, 32) creating respective first and second gathering chain assemblies, characterized by: the plurality of lateral extensions comprising a plurality of individual bristle blocks, each individual bristle block having a base, the base having bristles extending laterally outward from a front side of the base, a back side of the base removably, yet rigidly attaching to the respective first and second gathering chains (32, 34); whereby the bristles of the plurality of bristle blocks of the first gathering chain assembly provide a first substantially continuous conveying surface above and along the first side of the slot; and whereby bristles of the plurality of bristle blocks of the second gathering chain assembly provide a second substantially continuous conveying surface above and along the second side of the slot; and whereby the first and second substantially continuous conveying surfaces extend substantially across the width of the slot such that as the stalks of the row crop are pulled through the conveying surfaces, the bristles capture and prevent loose kernels of the row crop being harvested from falling through the slot. the plurality of lateral extensions comprising a plurality of individual bristle blocks, each individual bristle block having a base, the base having bristles extending laterally outward from a front side of the base, a back side of the base removably, yet rigidly attaching to the respective first and second gathering chains (32, 34); whereby the bristles of the plurality of bristle blocks of the first gathering chain assembly provide a first substantially continuous conveying surface above and along the first side of the slot; and whereby bristles of the plurality of bristle blocks of the second gathering chain assembly provide a second substantially continuous conveying surface above and along the second side of the slot; and whereby the first and second substantially continuous conveying surfaces extend substantially across the width of the slot such that as the stalks of the row crop are pulled through the conveying surfaces, the bristles capture and prevent loose kernels of the row crop being harvested from falling through the slot.