  In [math-ph/0107005] we have proven that the generating function for
self-avoiding branched polymers in D+2 continuum dimensions is proportional to
the pressure of the hard-core continuum gas at negative activity in D
dimensions. This result explains why the critical behavior of branched polymers
should be the same as that of the $i \phi^3$ (or Yang-Lee edge) field theory in
two fewer dimensions (as proposed by Parisi and Sourlas in 1981).
  -
  In this article we review and generalize the results of [math-ph/0107005]. We
show that the generating functions for several branched polymers are
proportional to correlation functions of the hard-core gas. We derive Ward
identities for certain branched polymer correlations. We give reduction
formulae for multi-species branched polymers and the corresponding repulsive
gases. Finally, we derive the massive scaling limit for the 2-point function of
the one-dimensional hard-core gas, and thereby obtain the scaling form of the
2-point function for branched polymers in three dimensions.
