  We have measured the distributions of the jet energies in e+e- --> qq^bar g
events, and of the three orientation angles of the event plane, using hadronic
$Z^0$ decays collected in the SLD experiment at SLAC. We find that the data are
well described by perturbative QCD incorporating vector gluons. We have also
compared our data with models of scalar and tensor gluon production, and
discuss limits on the relative contributions of these particles to three-jet
production in e+e- annihilation.
