  We report on Ferromagnetic-Resonance experiments in a single crystal of
La_0.8Sr_0.2MnO_3 in the temperature range from 4 to 300 K. The observed
anisotropy of the resonance line changes on crossing the transition from the
orthorhombic O-phase to the rhombohedral R-phase at T~100 K and indicates a
reorientation of the spins at about 130 K.
