  The n-string braid group of a graph X is defined as the fundamental group of
the n-point configuration space of the space X. This configuration space is a
finite dimensional aspherical space. A. Abrams and R. Ghrist have conjectured
that this braid group is a right angled Artin group if X is planar. We prove
their conjecture if X is a tree whose nodes all lie in a single interval of X.
