Marsilea is a genus of about 65 species of aquatic ferns of the family Marsileaceae . The name honors the Italian naturalist Luigi Ferdinando Marsilli (1656–1730).
These small plants have an unusual appearance and do not resemble the common fern. Common names include water clover and four-leaf clover because the long stalked leaves have four clover – like lobes and are either present above water or submerged.
Some Australian species of Sporocarps are very drought-resistant, surviving up to 100 years in dry conditions. When wet, the gelatinous interior of the sporocarp swells, splitting it and releasing a worm-like mass containing the sori, which eventually leads to germination and fertilization of the spores.
Marsilia hirsuta was introduced to the Azores, but was previously considered an endemic species, M. azorica
The sporocarps of some Australian species, such as Marsilea dramondi , are edible and were eaten by aborigines and early white settlers, who knew it as ngardu or nardu . Parts of Marsilia drummondii contain an enzyme that destroys thiamine (vitamin B1), which causes brain damage in sheep and horses . During a flood in the Gwydir river basin, 2,200 sheep died after eating nardu. However, three-quarters of the sheep that were affected responded to the thiamine injection. Thiamine deficiency from improperly prepared nardo can lead to starvation and death of Burke & Wills.  
The leaves of Marsilia crenata are part of Indonesia’s East Javanese cuisine, especially in the city of Surabaya. It is called Pesel Semangi and is served with spicy peanut and sweet potato chutney.
Some species in the genus, such as Marsilea crenata , Marsilea exarata , Marsilea hirsuta , and Marsilea quadrifolia , are grown in aquariums.
- Marsilia aegyptica Wild.
- Marsilia Encyclopoda A.Braun – Tropical Water Clover
- marcelia aposita launert
- Marsilia Burchelli A. Braun
- Marsilia capensis A.Braun
- Marsilia Coromandelina Wild.
- Marsilia crenata C. Presl
- Marsilia Crotophora DM Johnson
- Marsilia deflexa A.Braun
- Marsilia distrota A. Braun
- Marsilia Drummondi A. Braun
- Marsilea ephippiocarpa एल्स्टन
- Marsilia farinosa launert
- Marsilia fenestrata launert
- Marsilia Hirsuta R. Br.
- Marsilia macrocarpa C.Pressl
- Marsilia Macropoda Angleum . Former A. braun
- Marsilia minuta L. – Dwarf Water Clover
- Marsilia Mollis B.L. Rob. and Fernald
- Marsilia Mutica Met.
- Marsilia Nubica A. Braun
- Marsilia oligospora Gudd.
- Marsilia quadrifolia L. – European water clover
- Marsilia schlepina launert
- Marsilia unicornis longert
- Marsilia Vera Lauert
- Marsilia vestita hook. and Grave. – Hairy water clover.
- Marsilia villifolia Brem. and Obram. East Alston and Schelpe
- Marsilia villosa Kaulf . – Ihiʻihi (Hawaii)