Pollen and seed morphological data refute that Borreria hockii (R.D. Congo, Katanga) is synonymous to Spermacoce thymoidea (Southwest Angola, Huila). For the former, the necessary combination Spermacoce hockii is given; Spermacoce homblei, described from Katanga, is shown to be synonymous. The name Spermacoce thymoidea was also used for Zambian material from Mwinilunga that represents in fact a new species, Spermacoce stipularis, also collected from central Angola and Katanga. Spermacoce stipularis mainly differs from Spermacoce thymoidea in the presence of an elaiosome and in the type of pollen grain, and from Spermacoce hockii in the more slender and taller habit, the absence of heterophylly, and the smaller flowers. The value of the characters used in the taxonomy of the genus Spermacoce is briefly reviewed with special emphasis on the importance of seed and pollen data. The three species are restricted to high plateaus of the Zambezian regional center of endemism; they are geoxylic plants, a life form very common in the grass savannahs of these plateaus. Further comments on the ecology of the plateaus and their endemism are also provided.