The growth of planar jets is studied using the hydrogen bubble technique of flow visualization. A five-fold range of nozzle exit Reynolds number (1860 to 10,800) is considered. Generation of streaklines and timelines permits characterization of the process of vortex formation and coalescence. Both symmetrical and asymmetrical modes of vortex growth and coalescence, along with the resultant deformation of the jet core flow, are examined. Nascent and mature stage coalescence are defined and portrayed. Vortex axial transport velocity and frequency of formation of the vortices are evaluated for selected Reynolds numbers.