CALLA, in botany, a genus of the arum family (Araceae), comprising only one species (C. palustris), known as arum lily, water arum or wild calla, found widely in bogs in cool north tem perate and subarctic regions. It is a handsome plant, with heart shaped leaves, showy white flowering spathes and a fruit cluster of brilliant red berries. The well-known calla or calla lily of the gardeners is a species of Zantedeschia (q.v.). (See ARACEAE.)