  We studied dendritic side-branching mechanism in the experiment of
anisotropic viscous fingering. We measured the time dependence of growth speed
of side-branch and the envelop of side-branches. We found that the speed of
side-branch gets to be faster than one of the stem and the growth exponent of
the speed changes at a certain time. The envelope of side-branches is
represented as Y ~ X^1.47.
