  We report detailed shape measurements of the tips of three-dimensional
ammonium chloride dendrites grown from supersaturated aqueous solution. For
growth at small supersaturation, we compare two different models: parabolic
with a fourth-order correction, and power law. Neither is ideal, but the
fourth-order fit appears to provide the most robust description of both the tip
shape and position for this material. For that fit, the magnitude of the
fourth-order coefficient is about half of the theoretically expected value.
