cal·la 
(kălə)
(kălə)n.
1. A calla lily.
2. A marsh plant (Calla palustris) of northern temperate regions, having small, densely clustered, greenish flowers partly enclosed in a spreading white spathe. Also called water arum.
[New Latin Calla, genus name, from Greek kallaia, wattle of a cock, perhaps from kallos, beauty.]