  We study the grand-canonical solution of a system of hard polydispersed rods
placed on the square lattice using transfer matrix and finite size scaling
calculations. We determine the critical line separating an isotropic from a
nematic phase. No second transition to a disordered phase is found at high
density, contrary to what is observed in the monodispersed case. The estimates
of critical exponents and the central charge on the critical line are
consistent with the Ising universality class.
