Volume 25 of Flora North America is one of two volumes on grasses to be published in this series. Together they will provide a comprehensive, authoritative, illustrated account of this important group of plants. Most of the species treated are either native to North America north of Mexico or are introduced species that are now established in the region, but there are many that do not fit into these categories. Among the additional species are several that the USDA has identified as major weed threats; and others that are known only as cultivated plants, some being cultivated for their ornamental value, others as sources for human food or animal forage. For instance, volume 25 includes such ecologically important species as Big and Little Bluestem, economically important species of Sorghum and Corn, ornamental species such as Job's Tears and Hakonechloa, and noxious weeds such as Itchgrass. The volume includes identification keys, descriptions, line drawings, and ecological characteristics for each of the species; distribution maps for the native and established species; and a list of the synonyms currently in use for the accepted names. The treatments, each of which has been extensively reviewed, are based on a combination of original observations and critical review of the literature.