f4 O(90 Z777Z. JOURNAL OF THE ARNOLD ARBORETUM VOL. 58 APRIL 1977 NUMBER 2 SYSTEMATICS OF THE NEOTROPICAL GENUS CENTRADENIA (MELASTOMATACEAE) FRANK ALMEDA, JR. CENTRADENIA IS A WELL-DEFINED GENUS of subshrubs and suffrutescentperennial herbs comprising six taxa which are largely restricted to Mexicoand Central America. The genus is unique among Mesoamerican Melasto-mataceae in having basally oblique leaves; pyriform, clavate, or dolabri-form seeds with a conspicuous lateral raphe; and pronounced anisophylly.Despite its small size, comparatively limited range, and remarkable di-versity in androecial morphology, Centradenia has never been the subjectof a comprehensive study. Because previous knowledge of the genus hasbeen limited to regional floristic surveys, the limits and ranks of certaintaxa have remained controversial. This study was undertaken in an effortto clarify the confusion by providing new information on chromosomenumbers, ecogeographic distribution patterns, and the breeding systemsof selected taxa. Based on the cumulative information obtained from theseapproaches together with an evaluation of morphological criteria, I hererecognize four species (two of which are divided into two subspecies). TRIBAL AND GENERIC CONSIDERATIONS The genus Centradenia has been assigned by various authors to two ofthe five neotropical tribes of Melastomataceae with capsular fruits, theTibouchineae (Krasser, 1893) and the Microlicieae (Cogniaux, 1891;Hooker, 1867; Triana, 1871), Tribal disposition of genera in the familyhas rested heavily on characters such as capsule symmetry, position ofstaminal appendages, prolongation of the connective, and seed shape. Kras-ser apparently emphasized the ventral position of appendages when he rele-gated Centradenia to the Tibouchineae; Cogniaux, Hooker, and Triana,however, gave greater weight to seed shape when they assigned it to theMicrolicieae. Tribal limits, especially among the Microlicieae, Rhexieae, and Tibou-chineae, are not always clear. Consequently, tribal assignment often de-pends in large part upon which of the differences and similarities in stamensand seeds one chooses to emphasize. In a family such as the Melastomata-� President and Fellows of Harvard College, 1977.