Evolution of anatomical characters in Acianthera section Pleurobotryae (Orchidaceae: Pleurothallidinae).

Acianthera section Pleurobotryae is one of ten sections of the genus Acianthera and include four species endemic to the Atlantic Forest. The objective of this study was to describe comparatively the anatomy of vegetative organs and floral micromorphology of all species of Acianthera section Pleurobotryae in order to identify diagnostic characters between them and synapomorphies for the section in relation of other sections of the genus. We analyzed roots, ramicauls, leaves and flowers of 15 species, covering eight of the nine sections of Acianthera, using light microscopy and scanning electron microscopy.