Description: Rhizome usually long-creeping, often branched.
Sterile fronds borne at intervals along the rhizome; stipe varying in length depending on whether the plant is growing in standing water or not, stipe terminated by 4 leaflets (2 close pairs) that are narrow-cuneate to broadly fan-shaped, glabrous or pubescent; veins anastomosing.
Sporocarps stalked, arising at the base of or from the lower part of the stipe, solitary or in groups, usually densely hairy, variously shaped, often with 1 or 2 teeth near the summit of the stalk. Most species are widespread, especially in inland areas, in wet ground or standing water, often in areas subject to seasonal inundation.
Distribution and occurrence: World: c. 60 species, cosmopolitan. Australia: 8 species, all States.
Text by Peter G. Wilson
Taxon concept:
| | Key to the species | |
| 1 | Rhizomes and fronds virtually glabrous, a few hairs sometimes present at the base of the leaflets; body of sporocarp globose, lacking teeth | Marsilea mutica |
| Rhizomes and fronds variously hairy; sporocarps not globose, teeth present | 2 |
| 2 | Sporocarps with stalk 1.5–10 times the length of the body of the sporocarp | Marsilea drummondii |
| Sporocarps with stalk shorter than the length of the body of the sporocarp
Back to 1 | 3 |
| 3 | Upper side of the sporocarps flat or concave, the apex pointed; teeth 2, the lower one usually recurved | Marsilea exarata |
| Upper side of sporocarps flat or convex, the apex rounded; teeth 1 or 2, the lower one, when present, not recurved
Back to 2 | 4 |
| 4 | Teeth 2, triangular, ± equal; leaflets 5–13 mm wide, usually equally arranged | Marsilea hirsuta |
| Tooth 1, often a second, false, tooth is formed by the apex of the stalk; leaflets to 5 mm wide, unequally arranged and distinctly paired
Back to 3 | Marsilea costulifera |
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