Comparative Anatomy of the Moraceae and Their Presumed Allies

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Abstract
The secondary xylem from stems of 465 spp. in 165 genera representing 22 families centering about the Moraceae was examined. Interpreting the anatomical data given for each family in the light of the lines of specialization in the structures of the plant stele (such lines as those formulated for the evolution of vessel elements, fibrous tracheary elements, rays, wood parenchyma, etc.), together with a consideration of the facts from floral anatomy, nodal anatomy, floral morphology, and the available evidence from the fields of paleobotany and cytology, the following are some of the conclusions reached: The Hamamelidaceae are derivatives of the Magnoliales. The Casuarinales, Fagales, and Urticales are derivatives of the Hamamelidaceae. The Cunoniales are derivatives of the Magnoliales. The Rosales have been derived from some group in the Cunoniales. In the Urticales, the Ulmaceae are most primitive, the Moraceae less so, and the Urticaceae are least primitive. In the Moraceae, anatomical specialization seems to have proceeded from the sub-family Moroideae to the Artocarpoideae to the Conocephaloideae to the Cannaboideae. The tribe Fatoueae of the sub-family Moroideae appears to be the most primitive tribe in the family. In general, the evolutionary development of anatomical structures seems to be correlated with the evolution of floral structures.