Brachyelytrum is a small and morphologically distinct genus of grasses distributed throughout eastern North America and eastern Asia. In the past, plants in the genus have been variously treated as one to three taxa at the specific, subspecific, and varietal ranks. The taxonomy of Brachyelytrum has not been investigated across its entire geographic range. Based on herbarium and field studies, we present a revised taxonomic treatment. Morphological and label data were studied on approximately 665 herbarium sheets. A multivariate statistical analysis of 19 morphological characters, measured on 110 specimens representing both the morphological and geographical range of variation in Brachyelytrum, was conducted to investigate patterns of morphological variation and species limits. Scanning electron microscopy was used to search for taxonomically informative micromorphological characters. Geographic data were obtained from specimens and the literature and were plotted to determine the geographic distributions of characters and taxa. Based on a combination of morphological and phytogeographical data, we recognize three distinct species in Brachyelytrum. Brachyelytrum erectum and B. aristosum are distinguished by differences in lemma hair length and lemma width and have somewhat overlapping but ecologically distinct distributions in eastern North America, while B. japonicum is distinguished by its narrow leaf blades and long rachillas and is distributed in eastern Asia. A key to taxa is included.

Key words: Brachyelytrum, multivariate analysis, Poaceae, taxonomy