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The morphology and anatomy of the African monospecific genus Colletoecema E. Petit (Rubiaceae) is documented and illustrated (including wood anatomy, pollen morphology, gynoecial and exotestal structure). Morphological and anatomical comparison shows that Colletoecema differs in many aspects from the Psychotrieae (e.g., wood anatomy, seed structure). Consequently, the genus' provisional position in the Psychotrieae cannot be maintained. Morindeae, the second tribe Colletoecema has been associated with, has a different gynoecial structure. The oily endosperm and large embryo of Colletoecema is found in several genera that often were or still are included in the Psychotrieae or Morindeae (Trichostachys, Saldinia, Ronabea, and Lasianthus). However, they differ in several other aspects, which makes a close relationship doubtful. Colletoecema exhibits a unique combination of characters including axillary inflorescences, banded parenchyma in the wood, ovules attached around the middle of the septum, bilocular pyrenes, seeds with oily endosperm and large embryo, and verrucate exotestal thickenings, not encountered elsewhere in the Rubioideae. A cladistic analysis based on nucleotide sequence variation in the rps16 intron (chloroplast DNA) confirms that Colletoecema is related neither to Psychotrieae nor to Morindeae. Colletoecema appears as a sister genus of Ophiorrhiza in a weakly supported clade among the basalmost clades of the subfamily Rubioideae, but there is very little morphological support for this relationship.Key words: anatomy, chloroplast DNA, cladistics, morphology, Psychotrieae, Rubioideae.

Coccocypselum is a small neotropical genus of creeping herbs belonging to the Rubiaceae (Rubioideae). A recent macromolecular study suggested a previously unknown relationship between Coccocypselum and two other neotropical genera, Declieuxia and Hindsia, but the morphological evidence for this relationship was obscure. In the present paper, morphological characters supporting the conclusions from macromolecular data are presented. The most important similarities between Coccocypselum, Declieuxia, and Hindsia are found in their pollen and stipule morphology. Pollen of the three genera share a typical exine ornamentation, called a complex reticulum, which consists of a psilate suprareticulum and spinulate infrareticulum. In some specimens of Hindsia longiflora, a transitional stage between a complex reticulum and a simple, spinulate reticulum is encountered. The interpetiolar stipules of Hindsia, Declieuxia and Coccocypselum have an identical basic structure: they bear a central, colleter‐tipped awn that extends downwards to the next node as a distinct stem ridge. Some less conspicuous similarities of habit, calyx, and corolla are also discussed. The morphological data are, in part, confirmed by distributional data, Declieuxia and Hindsia having a remarkably congruent centre of diversity in the southeast of Brazil. It is concluded that the macromolecular data, combined with this new morphological and distributional evidence, justify an extended tribe Coccocypseleae, comprising the genera Coccocypselum, Hindsia, and Declieuxia.

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