The pollen morphology of eight Macroptilium species occurring in Mexico and Central America is described by means of light and scanning microscopy. In this region, members of the genus have pollen grains 3colporate, mediumsized, with polar shapes from prolatespheroidal, suboblate to oblatespheroidal. Differences in ectoaperture (length, apex shape and membrane), ornamentation, margo, and the outline in polar side identify two pollen types: Type I. Pollen with small colpi (brevicolpate), margo thickened, apex of the ectoaperture round, membrane granular, polar outline convex angular, exine tectate or semitectate, apocolpium punctate or rugulate, and mesocolpium microreticulate or rugulate. Species of section Microcochle, including M. gibbosifolium, M. pedatum, and M. supinum are characterized by this pollen type. Type II. Pollen with long colpi (longicolpate) margo nonthickened, apex of the ectoaperture acute, membrane granular, pollen outline circular to semiangular, exine tectate or semitectate, apocolpium punctate to foveolate, and mesocolpium microreticulate to foveolate. Species of section Macroptilium comprising, M. atropurpureum, M. erythroloma, M. gracile, M. lathyroides, and M. longipedunculatum are distinguished by this pollen type. Palynological descriptions of five species of Macroptilium are provided for the first time.
