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Shoreline Plants  

 
Species: Marsilea vestita Hook & Grev. (formerly called: Marsilea mucronata A. Br.), pepperwort, clover-fern, water-clover
Family: Marsileaceae

Because of their four-part hairy leaves, pepperwort plants look like clusters of aquatic four-leaf clovers, but they are actually ferns. Pepperwort can grow either on wet ground or in shallow water. These small plants arise from horizontal rhizomes with only the leaves and slender leaf-stalks visible above the surface of the substrate or shallow water. Several small hairy, nut-like spore cases can often be observed at the base of the plant.

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Leaf: Clover-like leaves are composed of four leaflets; each leaflet is 5-15 mm wide and 3-17 mm long. The leaf surface may be either densely hairy or smooth. Depending on water depth, the leaves are emergent or float at the ends of slender 2-20 cm long leaf stalks.

Stem: The thin horizontal rhizome is underground in terrestrial plants or submerged in aquatic plants. Pepperwort plants have no upright stems.

Flower: No flowers. Spores develop in solitary, generally hairy spore cases that arise on short stalks (to 25 mm long) from the leaf bases. Spores are produced when the plants are mostly out of the water, either when the water level drops, or throughout the year if the water is always shallow.

Fruit: Hairy, nut-like spore-cases, 3-8 mm long, resemble peppercorns. When the spore cases open, they release a gelatinous substance containing the spores.

Root: Thin and fibrous, emerging from slender rhizomes.

Propagation: Reproduces by spores and vegetatively by rhizomes.

Importance of plant: Spore cases are eaten by waterfowl, and the plant provides fish shelter.

Distribution: Occurs west of the Mississippi River. There are more than 45 species of Marsilea with nearly worldwide distribution.

Habitat: Creekbeds, wetlands, seasonal pools, ditches, flood basins, and shores of lakes and streams. Adapted to fluctuating water levels and is tolerant of alkaline conditions.

May be confused with: Clovers (Trifolium spp.) have similar leaves, but have large compact flower heads. Clovers are never aquatic, although a few (e.g. T. wormskjoldii) may be found in wetlands. Wood sorrel (Oxalis oregana) also has similar leaves, but has leaflets of three rather than four. Wood sorrel is a forest species and typically not found in aquatic habitats. Another related species (Marsilea oligospora) also may be found in eastern Washington. It may be distinguished from pepperwort by detailed microscopic examination of the spore cases.

Photographs: Marsilea vestita

Line Drawings: None available 


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