  We interpret D-strings at the bottom of the warped deformed conifold as
axionic strings in the dual cascading SU(N+M) x SU(N) gauge theory. The axion
is a massless pseudo-scalar glueball which we find in the supergravity
fluctuation spectrum and interpret as the Goldstone boson of spontaneously
broken U(1) baryon number symmetry. The existence of this massless glueball,
anticipated in hep-th/0101013, supports the idea that the cascading gauge
theory is on the baryonic branch, i.e. the U(1)_B global symmetry is broken by
expectation values of baryonic operators. We also find a massless scalar
glueball, which is a superpartner of the pseudo-scalar. This scalar mode is a
mixture of an NS-NS 2-form and a metric perturbation of the warped deformed
conifold of a type first considered in hep-th/0012034.
