Measurements are presented of txcitation tmnsport ir i E quasi-l-D solid using time-resolved laser spectroscopy. Energy migration xs a function of temperature and dopant concentration is describable in terms of step-%ise incoherent trmsfer US~II~ a I-D sampling function_ The data indicate the effect of a superelchange interaction between clusters. Real I-D solids, if they exist. provide an opportunity to examine the detarled nature of excitation transport-Dynamically speaking, finite cross-chain interactions may alter excitation transport dramatically and conventional cw optical spectra will not reveal the fiier features of the motion_ We present new observations on the transient behavior for electronic excitation transport [I] in a disordered quasi-l-D system (isotopic&y mixed crystaliine 1 +dibromonaphthalene; DBN). By probing different portions of the irhomogeneously broadened lines with narrow-band iaser excitation (=9 GHz), we find no evidence of a "mobility edge"_ Instead, the data illustrate the direct role of superexchange between impurity cIusters. DBN was chosen because the interaction between molecuies is short range and the disorder can be '&controlled" by doping DBNJz6 with DBNd6, thus forming barriers in the crystal_ In the limit of heavy disorder, we fmd that the traspnort of DBN?z6 triplet excitation and effective dimensional&y can be described by (a) a sampling function with time-dependent (f-l/") energytransfer rate, and (bj a 1-D configuration-weighted average superexchange matrix element_