P OLLEN and seed morphology of 19 species representing 12 genera of the Mimosoideae and Caesalpinioideae was studies using light and electron microscopy. Observed variations were recorded comparatively in a data matrix and analyzed numerically by the PRIMER Ver.6 program package for cluster analysis. The ensuing dendrogram indicates the division of the species into two main groups. One group includes all members of the Mimosoideae together with all three species of Senna from the Caesalpinioideae. The remaining eight species of the latter subfamily constitute the second group. Apart from the deviation of Senna from the Caesalpinioideae, the distinction between the two subfamilies seems corroborated by differences in pollen and seed morphology. Senna is distinct from Cassia and deserves generic rank. The generic concept in the two subfamilies is taxonomically sound since the group of species representing one genus are attached together before joining those of other genera. Individual genera (such as Calliandra) can be singled out by their pollen aggregations.