• (n.) A longitudinal rank, or row, of leaves along a stem.
Or·thos'ti·chy noun ; plural Orthostichies . [ Ortho- + Greek ... row.] (Botany) A longitudinal rank, or row, of leaves along a stem. 
orthostichy (s), orthostichies (pl) A longitudinal rank, or row, of leaves along a stem.
a vertical rank or row. · an arrangement of members, as leaves, at different heights on an axis so that their median planes coincide.