Three new species of the Neotropical genus Barbacenia (Velloziaceae, Pandanales) from Tocantins, Brazil, are described and illustrated, based on morphology and leaf anatomy. The known species richness of the genus is mapped within the countries of South America and the states of Brazil.

Globally, the Cerrado is the most diverse savanna in terms of plant species, as well as one of the most threatened as the result of human impact; it is therefore considered a priority area for conservation. Some areas of the Cerrado have still not been subject to botanical collections and detailed studies, the Jalapão region being one of these. We describe four recently rediscovered species previously known only from type specimens collected at least 160 years ago: Hyptis caduca Epling (Lamiaceae), Duguetia rotundifolia R.E.Fr. (Annonaceae), Diospyros ovalis Hiern (Ebenaceae) and Rhabdodendron gardnerianum (Benth.) Sandwith (Rhabdodendraceae). Comments on their ecology, conservation status and occurrence are provided, together with a distribution map. New morphological data have been recorded, and all species are considered to be under some degree of threat. These rediscoveries highlight the importance of further fieldwork in poorly sampled and highly biodiverse regions such as Jalapão and neighbouring areas, as well as the urgent need for conservation of the highly threatened Cerrado biome.

Three new corticolous Diorygma species are described from Brazil. Diorygma incantatum has transversely 29–31-septate, filiform ascospores 105–108×6 µm, and produces an unidentified substance with Rf 44 in solvent C. Diorygma pauciseptatum produces norstictic and connorstictic acids and has transversely 7–9-septate, I+ blue-violet, large ascospores 28–32×7 µm, surrounded by a gelatinous sheath c. 2 µm wide that is often somewhat expanded at one end. Diorygma tocantinense contains protocetraric acid and has muriform, broadly fusiform ascospores with rounded ends, 24–40×10–15 µm, surrounded by an gelatinous sheath up to c. 5 µm wide that is somewhat expanded at central parts of the ascospore. A revised world key is given to all currently known species of Diorygma.

Pleonotoma orientalis Sandwith (Bignoniaceae), a poorly known species, is lectotypified, illustrated for the first time and a distribution map is provided. Pleonotoma orientalis Sandwith var. ratteriana Proença & Farias from the Jalapão area (State of Tocantins, Central Brazil) is described and illustrated. The new variety is apparently identical to the typical variety in floral characters but distinct in its ternate-tripinnate leaves with numerous, minute, slightly thickened leaflets, and fruits with rounded or obtuse tips. The collections of this new variety increase its range c.400 km S from Northern Brazil (Maranhão and Pará) into Tocantins in Central Brazil.