The solar granulation, with its horizontal temperature fluctuations, and its associated velocity field, is a consequence of overshooting convective motions. Theoretical estimates of the magnitude of the temperature fluctuations and mass fluxes involved were obtained in a recent paper (Nordlund, 1976, Astronomy & Astrophys. 50, 23). Here, a simple model of the instantaneous granular velocity field is presented, and the effects of this velocity field on photospheric spectral lines are described.