Cyperus is a Pantropical genus and the second richest in species in Cyperaceae. It encompasses about 550 species worldwide, with about 100 of these occurring in Brazil. Studies on the taxonomy of this genus are scarce and punctual in Brazil. In this study, the occurrence of species was surveyed through 27 collecting expeditions across different regions in the state of Rio Grande do Norte and analyzis of specimens of several herbaria. Twenty four species of Cyperus were identified, including six new occurrences and one new species, here described, but that will be properly published in other work. This study includes a dichotomous key for the identification of the species, as well as illustrations, descriptions, taxonomic comments and geographical distribution.

This article describes the riparian vegetation of a river in the Rio Grande do Norte state for the first time. This is a seasonal river in the semiarid region of the Caatinga biome. The study is based on data from herbarium collections and new expeditions from July 2007 to October 2008. Two hundred and forty seven taxa were recorded and of these, 116 are herbs and three of which are epiphytes, 25 sub-shrubs, 77 shrubs or trees, 26 lianas, one parasite, and two palms. This list of species of riparian vegetation in the river Apodi-Mossoró was compared with only two available lists from rivers in the northeast with similar environmental characteristics and showed a low similarity. This study points to the need for preservation of the species and remnants of riparian vegetation of the river Apodi-Mossoró and to increase efforts in the study of this vegetation type.

New records of Poaceae in Brazil and Bolivia are documented from expeditions, collections and review of herbarium specimens. Eleven new records are confirmed and comments, IUCN Threatened Species Categories and illustrations for these taxa are provided. Mesosetum comatum and M. filifolium are new records for Brazil, and M. ansatum is a new record for Bolivia. Paspalum burchellii, P. lepton, P. oteroi and P. trinitense are new records for Bolivia.

Mesosetum is a Neotropical genus with 25 species, and 21 of them occur in Brazil. Mesosetum forms a clade closely related with Keratochlaena rigidifolia and Tatianyx arnacites. The objective of this work was to establish the taxonomic value of the upper anthecium micromorphology for the group. A total of 96 specimens, representing all Mesosetum species (except M. wrightii), K. rigidifolia and T. arnacites were examined under a scanning electron microscope (SEM). PCA and UPGMA analysis were applied using the micromorphological characters. Fifithteen useful taxonomic characters were identified. We highlight the following characters to distinguish the Mesosetum species: the presence, type and distribution of papillae on the abaxial surface of the upper lemma; the presence of unicellular macrohairs and bicellular microhairs; presence or absence of silica cells and the structure of the germination lid. The present work shows that the micromorphological characters identified are important taxonomically at the specific level, allowing the species identification in many cases.

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