ARUNDO, in botany, a genus of the triandria digynia class. The calix consists of two valves, and the floccules are thick and downy. There are six species of arundo, four of which are natives of Britain, viz. the phragmitis, or common red-grass; the calamogrostis, or branched red-grass; the epigejos, or small red-grass; and the arenaria, or sea red-grass.