  The data on the dispersion of the magnetic excitations of CuGeO_3 in the
spin-Peierls dimerized phase are analyzed. On the basis of the lattice
structure it is shown that even along the chains the $d=2$ character cannot be
neglected. The symmetry of the dispersion differs from the one assumed so far.
The magnetic resonance data is reinterpreted. The possibility of interchain
rather than intrachain frustration is discussed.
