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Tracheid Dimorphism: A New Pathway In Evolution Of Imperforate Tracheary Elements, Sherwin Carlquist

Aliso: A Journal of Systematic and Floristic Botany

Certain dicotyledon families characteristically have tracheids as their imperforate tracheary element type. Of these, six families are anomalous by having septate (or nonseptate but living) fiber-tracheids or libriform fibers coexisting with the tracheids in some species or genera (Austrobaileyaceae, Celastraceae, Convolvulaceae, Ericaceae, and Grossulariaceae, and Rosaceae). Data from the literature and original data on wood anatomy of these families are presented. A theory of tracheid dimorphism is developed to account for these instances of tracheids combined with fiber-tracheids or libriform fibers. According to this theory, septate or living fiber-tracheids or libriform fibers are produced in addition to tracheids, starting with …