Rhexia

Abstract: Rhexia is a relatively small genus of the Melastomataceae, a pantropical family of approximately 150 genera and 4000 species. The members of this family are, in general, readily recognized, for in addition to their one basic type of floral structure, the leaves are characteristically opposite and have a pronounced palmate-arcuate type of venation. Consequently, in those parts of the tropics where the family is well represented, it contributes a distinctive element to the flora. None of the species of this large family is known to be of any appreciable economic importance. Although a few become large trees, their sporadic and infrequent occurrence prohibits even these from being commercially important as timber. Medicinal substances are unknown in the melastomes, and edible products are limited to the fleshy fruits of only a few species. Although some are cultivated as ornamentals, none has ever become very popular or extensively planted. The family is represented in the United States only by Rhexia and a single West Indian species, Tetrazygia bicolor (Mill.) Cogn., which extends into southern Florida. The genus Rhexia is known only from the United States, except for the southern extension of Rhexia cubensis into the West Indies and the northern extension of Rhexia virginica into Canada. Although Rhexia has been the subject of several revisions during its history, the genus has never been adequately monographed. The limits and rank of certain taxa have continued to be a source of disagreement, and some species are little known or have never been evaluated since they were originally described. Many of the specimens cited herein were specifically collected for this study by R. B. Channell, D. Demaree, E. S. Ford, R. K. Godfrey, C. E. Wood, and the author. The majority of these collections (including those supporting experimental data) are preserved in the Herbaria of Duke University and the Florida Agricultural Experiment Station. However, most of the material examined in the course of this study was borrowed from the following institutions:2

Abstract: The Melastomataceae collected by Giuseppe Raddi (1770-1829) during his expedition to Brazil (1817-1818) and housed at Fl and PI are studied. The collections typify names in the genera Bertolonia Raddi, Leandra Raddi, Melastoma L. and Rhexia L. For 22 species we provide information about types, nomenclature, taxonomy and geographical distribution.

Abstract: The floral anatomy of five taxa of Melastomataceae, namely, Memecylon edule, M. guinensis, M. capitellatum, Rhexia marina and Tabouchina semidecandra has been studied. The regular, epigynous flowers are tetramerous in Memecylon edule, M. capitellatum, Rhexia marina and pentamerous in M. guinensis and Tabouchina semidecandra. The floral parts as well as their traces show varying degrees of adnation. The septate condition of the ovary in Rhexia marina and Tabouchina semidecandra and the presence of rudimentary septa in Memecylon edule, M. guinensis and M. capitellatum reveal that the central placentation in the family is derived from axile or anatomically parietal ancestry. The carpels are 3-traced in Memecylon edule, M. guinensis and M. capitellatum and 5-traced in the rest. The style is vascularized by the dorsal bundles in Memecylon species and by the common median laterals in Rhexia marina and Tabouchina semidecandra.

Abstract: Comolia is a neotropical genus currently represented by 10 accepted species. Since the description of the genus, 47 names have been published within it. When investigating these names, we found that some of them needed to be typified. The aim of the present study was to provide the nomenclatural treatment for Comolia, including a list of all synonyms related to its species, typifications and nomenclatural comments, when necessary. Thirteen lectotypes and one neotype are designated here. Six names were lectotypified using two illustrations. In addition, we synonymized C. ovalifolia var. blanchetiana and C. ovalifolia var. denudata under C. ovalifolia, and we typified Melastoma rhexioides and exclude it from Comolia.