  Closed bosonic string theory on toroidal orbifolds is studied in a Lagrangian
path integral formulation. It is shown that a level one twisted WZW action
whose field value is restricted to Cartan subgroups of simply-laced Lie groups
on a Riemann surface is a natural and nontrivial extension of a first quantized
action of string theory on orbifolds with an antisymmetric background field.
