A premixed flame, propagating away from a point ignition source into an unlimited domain displays an increasing flame speed after the flame size has grown beyond a transition radius. Experiments by Gostintsev et alare described by the relation R = R1+ At3/2, where t is the time from ignition and, where SLis the flame burning velocity and is the thermal diffusivity. The non-dimensional function a() is determined from the experimental results to be equal to 0.0022, where is the density ratio across the flame.