Free Floating Plants  

Species: Riccia fluitans L., slender riccia
Ricciocarpus natans L., purple-fringed riccia
Family: Ricciaceae

Slender riccia and purple-fringed riccia are small leaf-like plants that are found floating on still water, often with duckweeds (Lemna sp., Spirodela sp.) and watermeal (Wolffia spp.). Slender riccia is found in tangled masses just below the water surface. It is narrow and flattened with forked, ribbon-like branches. A few white, root-like structures sometimes appear on its underside. Purple-fringed riccia is a green, lumpy, fan-shaped plant with scalloped edges and numerous dangling purple root-like structures (rhizoids). It floats on the water surface unless stranded along shorelines.

Both of these plants are liverworts. Liverworts are different from most other plants described in this manual in that they lack vascular tissues for transporting water and nutrients within their bodies. They are small, many less than 2 cm, and lack stems, flowers, and roots. The name "liverwort" dates back to the ninth century when it was thought the liver-shaped plants might be useful in treating liver diseases.

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Leaf: Green, leaf-like plant body (thallus). Slender riccia: flat, branched, and ribbon-like, up to 2 cm long and 0.5-1 mm wide, growing in fibrous-looking clumps. Few or no white root-like structures. Purple-fringed riccia: approximately 1 cm long, fan-shaped grooved lobes with fluted or scalloped edges. Many brownish-purple root-like structures (rhizoids) on the underside of the thallus. The upper side has a roughened texture with many tiny bumps.

Stem: None.

Flower: None.

Fruit: None. Microscopic spores are produced in tiny spore-producing organs embedded within the thallus.

Root: Fine, root-like structures (rhizoids) absorb water and nutrients, and sometimes anchor the plants. Slender riccia: few if any, white rhizoids. Purple-fringed: numerous brownish purple rhizoids.

Propagation: Spores and budding (a new plant forms from a vegetative outgrowth of a mature plant).

Importance of plant: Food for ducks and birds; provides habitat for aquatic insects and invertebrates.

Distribution: Both occur nearly worldwide.

Habitat: Mostly floating in sheltered shallow water of ponds, pools, and swamps that tend to be warm or nutrient enriched. Sometimes stranded and anchored along shorelines. Often found growing with duckweeds (Lemna sp., Spirodela sp.) and Mexican water-fern (Azolla mexicana).

May be confused with: Duckweeds (Lemna sp., Spirodela sp.) and Mexican water-fern (Azolla mexicana). These species do not have the twice-branched, ribbon-like leaves of slender riccia, or the purple rhizoids of purple-fringed riccia.

Photographs: Closeup of Ricciocarpus natans

Line Drawings: Ricciocarpus natans, Riccia fluitans

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