Marsileaceae
| Marsileaceae Temporal range: Lower Cretaceous to recent |
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| Pilularia (top) and Marsilea (bottom) | |
| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta |
| Class: | Polypodiopsida / Pteridopsida (disputed) |
| Order: | Salviniales |
| Family: |
Marsileaceae Mirb. |
| Genera | |
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The Marsileaceae /mɑːrsɪliˈeɪsiː/ are a small family of heterosporous aquatic and semi-aquatic ferns, though at first sight they do not physically resemble other ferns. The group is commonly known as the "pepperwort family" or as the "water-clover family" because the leaves of the genus Marsilea superficially resemble the leaves of a four-leaf clover (a flowering plant). Leaves of this fern have sometimes been used to substitute for clover leaves on Saint Patrick's Day. In all, the family contains 3 genera and 50 to 80 species with most of those belonging to Marsilea.
Members of the Marsileaceae are aquatic or semi-aquatic. Plants often grow in dense clumps in mud along the shores of ponds or streams, or they may grow submerged in shallow water with some of the leaves extending to float on the water surface. They grow in seasonally wet habitats, but survive the winter or dry season by losing their leaves and producing hard, desiccation-resistant reproductive structures.
There are only three living genera in the family Marsileaceae. The majority of species (about 45 to 70) belong to the genus Marsilea, which grows worldwide in warm-temperate and tropical regions.Marsilea can be distinguished from the other two genera by the presence of four leaflets on each leaf, although some species occasionally produce six leaflets per leaf. A second genus Regnellidium includes a single living species that grows only in southern Brazil and neighboring parts of Argentina; it has only two leaflets per leaf. The third genus Pilularia grows widely in temperate regions of both the northern and southern hemispheres. Its leaves do not subdivide into leaflets but are slender and tapered to a point, so that it is often overlooked and mistaken for a grass. There are only about five species known.
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