The genus Marsilea includes about 60 species of aquatic ferns, adapted to amphibious habitats. It is characterized by 4 heart-shaped pinnae, arranged in a cross, that make it look like a clover. The species distribution is subcosmopolitan, 3 species in western Europe, including 2 in France (protected species). The stipes are thin, their length adaps to the water level. Spores are in sporocarps, small elongated capsules on the stipe base.