  We display the vertex operators for all states in the conformal supergravity
sector of the twistor string, as outlined by Berkovits and Witten. These
include `dipole' states, which are pairs of supergravitons that do not
diagonalize the translation generators. We use canonical quantization of the
open string version of Berkovits, and compute N-point tree level scattering
amplitudes for gravitons, gluons and scalars. We reproduce the Berkovits-Witten
formula for maximal helicity violating (MHV) amplitudes (which they derived
using path integrals), and extend their results to the dipole pairs. We compare
these trees with those of Einstein gravity field theory.
