  In 1993, Chemin proved that vorticity possessing negative Holder regularity
in directions given by a sufficient family of vector fields (striated
regularity) maintains such regularity for all time when measured against the
push-forward of those vector fields. Later work of Gamblin and Saint Raymond,
and of Danchin, established analogous results in higher dimension. We give an
alternative proof of these results, and establish the propagation of striated
regularity of the Lagrangian velocity in a positive Holder space.
