European Water Clover

European water clover, Marsilea quadrifolia, is an aquatic fern of the family Marsileaceae native to Europe and temperate Asia, growing rooted in the mud of ponds and slow-moving water with its four-lobed, clover-like fronds floating or held just above the surface. Unlike most ferns, it produces two distinct types of spores contained in hardened, bean-shaped structures called sporocarps, and the species has become an invasive aquatic weed in parts of North America, introduced through the aquarium and water-garden trade.