  We present an implementation of the hierarchical tree algorithm on the
individual timestep algorithm (the Hermite scheme) for collisional $N$-body
simulations, running on GRAPE-9 system, a special-purpose hardware accelerator
for gravitational many-body simulations. Such combination of the tree algorithm
and the individual timestep algorithm was not easy on the previous GRAPE system
mainly because its memory addressing scheme was limited only to sequential
access to a full set of particle data. The present GRAPE-9 system has an
indirect memory addressing unit and a particle memory large enough to store all
particles data and also tree nodes data. The indirect memory addressing unit
stores interaction lists for the tree algorithm, which is constructed on host
computer, and, according to the interaction lists, force pipelines calculate
only the interactions necessary. In our implementation, the interaction
calculations are significantly reduced compared to direct $N^2$ summation in
the original Hermite scheme. For example, we can archive about a factor 30 of
speedup (equivalent to about 17 teraflops) against the Hermite scheme for a
simulation of $N=10^6$ system, using hardware of a peak speed of 0.6 teraflops
for the Hermite scheme.
