Development of side branching in dendritic crystal growth

The growth of dendritic crystals of ${\mathrm{NH}}_4$Br from supersaturated solution has been studied in a way that allows high-resolution measurements of the early stages of side branching. The branches are found to be nonperiodic at any distance from the tip, with apparently random variations in both phase and amplitude. Side branches on opposite sides of the dendrite are imperfectly correlated. The rms side-branch amplitude is an exponential function of distance from the tip, with no apparent onset. The implications of these results for several theories of the stability of growing dendrites are discussed.