XVI International Botanical Congess

Aciotis is an herbaceous group that is distributed from southern Mexico to northern Bolivia and southeastern Brazil. Using morphological data obtained from herbarium material and from field observations I have reduced the 42 previously recognized species to 13. Of these, two are new a third is a new combination. A group of species of Aciotis (A. caulialata, A. indecora, and A. purpurascens) has thyrsoid inflorescences and indehiscent berry-like fruits, a second group (A. annua, A. ornata, A. polystachya, and A. wurdackii) has cymose inflorescences and dry dehiscent capsules. The remaining species (A. acuminifolia, A. circaeifolia, A. ferreirana, A. olivieriae, A. paludosa and A. viscida) have combinations of characters that do not allow their placement in either group. It seems that there is a possible correlation of the morphological characters of these two main groups with chromosome numbers and geographic distribution. The foveolate testa and the indehiscent berry-like fruits of some species of Aciotis make its placement in Melastomeae (including Tibouchineae) at least doubtful.