text: I think this is referring to the epiphyseal line that forms after full maturation of the bone.  The "growth plate" that we have as children (epiphyseal plate, or growth plate) in long bones such as the femur contain cartilage which allows our bones to elongate - making us taller as we grow.  When we reach our maximum height, the epiphyseal plate replaces cartilaginous tissue with bony tissue.  After this transition, the plate is referred to as the epiphyseal line and growth of the bone stops.