Thirty four species of Aristida L. were confirmed so far for Brazil, 13 of them exclusives of this area. Most are related to two general patterns of geographical distribution: the tropical and the subtropical. Both include species with a broad distribution and species with a limited distribution. Seven taxonomic characters are analysed and correlated to the species distribution: type of inflorescence; relative lenght of the glumes; and lemma: column, callus, articulation, ventral groove and awns. As a general rule, the species which occur in Northern and Central Brazil present a more remarkable morphological discontinuity than the species from the South, and can more easily be differentiated in the field. A list of the species, their geographical distribution and a discussion about the 7 taxonomic characters mentioned above, including illustrations of the latter, are presented.
Diversity; geographical distribution; Gramineae; Aristida