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The Nut Beds Flora of the Clarno Formation, dated at about 44 million years, is one of the most diverse fossil plant assemblages of North America, and contains fruits, seeds, woods, and leaves. The middle Eocene was a globally warm climatic interval and the diversity and composition of the Nut Beds fossil flora is considerably greater than that of the site’s present-day arid semi-desert vegetation. Based upon examination of more than 600 samples of permineralized woods, 66 genera and 76 species are recognized, making the Nut Beds wood assemblage the most diverse fossil wood assemblage ever described from a single locality. The Nut Beds woods provide a dataset useful for systematic, evolutionary, biogeographic, and paleoecologic studies, and complement the data already provided by the rich co-occurring fruit and seed assemblage (145 genera, 173 species). Some families are known only from woods (Cercidiphyllaceae, Malvaceae sl, Ginkgoaceae, Taxodia ceae). Others are known from both wood and fruits and seeds (Aceraceae, Alangiaceae, Anacardiaceae, Annonaceae, Araliaceae, Betulaceae, Fagaceae, Hamamelidaceae, Juglan daceae, Lauraceae, Leguminosae, Magnoliaceae, Platanaceae, Rosaceae, Sabiaceae, Sapin daceae, Ulmaceae sl, Vitaceae, Palmae, Pinaceae). The discussion of Nut Beds Meliosma (Sabiaceae) woods includes new information on wood anatomical groups within extant Meliosma. Within these shared families, comparison of the fruits and seeds and wood shows: 1) similarity in relationships to modern genera (Hamamelidaceae, Rosaceae, Pina ceae); 2) woods are more diverse than fruits/seeds …