The study of climatic effects in trees has two closely related objectives. One seeks to evaluate the importance of the various factors which influence tree growth; the other studies ring widths as an indicator of climatic history. Each of these can well supplement the other. Fundamental differences in emphasis can result, however, from these different objectives. For example, the first problem, which has been extensively treated by botanists, demands an equal study of all forest sites, while the second leads to a search for those special sites which permit the tree-ring series to reveal past climate most clearly. It is this latter, dendrochronologic type which is the approach of this paper. The need of strong crossdating in treering series which are to be studied as climatic indicators has been especially emphasized by Douglass ('20, '41a); the results of his work from the general ecological standpoint have been outlined recently by the writer ('41a). The purpose of the present study is to investigate in some detail the possibilities of crossdating in pines in the state of Arkansas, partly in order to establish a tree-ring chronology of climate for that region, and partly for the light it might cast on the complex problem of dating the moundbuilder and other ruins of the Mississippi Valley by means of the rings in ancient building timbers.