  We have investigated the time dependence of remanent magnetostriction in a
(La,Pr)$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ single crystal, in order to examine
the slow dynamics of lattice distortion in bilayered manganites. A competition
between double exchange and Jahn-Teller type orbital-lattice interactions
results in the observed lattice profile following a stretched exponential
function. This finding suggests that spatial growth of the local lattice
distortions coupled with e$_{g}$-electron orbital strongly correlates with the
appearance of the field-induced CMR effect.
