Background and aims – The identity of Diodia assurgens K.Schum. is unclear and the taxon has never been studied in detail since its description. In the present paper we aim to clarify its status and taxonomic position. Methods – Normal practices of herbarium taxonomy have been applied to study all herbarium material available. Pollen of Diodia assurgens and Diodia s.str. species was studied using the acetolysis method. Key results – The comparative morphological study clearly shows that Diodia assurgens K.Schum belongs to the genus Spermacoce s.str. and that it should be excluded from Diodia s.str. The new name Spermacoce spiralis Bacigalupo & E.L. Cabral is proposed and a lectotype is designated. The species is also described and illustrated. The palynological characters of Spermacoce spiralis agree well with those observed in other species of Spermacoce s.str.

DIODIA; RUBIACEAE; SPERMACOCE; SPERMACOCEAE