  This paper reports a series of measurements that characterize the directional
dependence of the scintillation response of crystalline anthracene to incident
DT neutrons, DD neutrons, Cs-137 gamma rays, and, for the first time, cosmic
ray muons. The neutron measurements give the amplitude and pulse shape
dependence on the proton recoil direction over one hemisphere of the crystal,
confirming and extending previous results in the literature. In similar
measurements using incident gamma rays, no directional effect is evident, and
any anisotropy with respect to the electron recoil direction is constrained to
have a magnitude of less than a tenth of that present in the proton recoil
events. Cosmic muons are measured at two directions, and no anisotropy is
observed. This set of observations indicates that high dE/dx is necessary for
an anisotropy to be present for a given type of scintillation event, which in
turn could be used to discriminate among different hypotheses for the
underlying causes of the anisotropy, which are not well understood.
