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Frog's-Bit Family

The frog's-bit or tape-grass family (Hydrocharitaceae) is a relatively small group of herbaceous, aquatic, monocotyledonous plants, occurring in fresh and marine waters. There are about 100 species in the frog's-bit family, distributed among 15 genera.

The flowers of members of this family are water pollinated, shedding their pollen into the water, which disperses it to the stigmatic surfaces of other flowers.

Several species in this family are native to North America. The elodea, or Canadian water-weed (Elodea canadensis), is a common aquatic plant in fertile, calcium-rich ponds, lakes, and other still waters. The elodea is a monoecious plant, meaning the male and female functions are carried out by different plants. The leaves of elodea occur opposite each other on the stem, or in whorls.

The tape-grass (Vallisneria americana) is also a native aquatic plant of non-acidic lakes and ponds. This species is also dioecious. The tape-grass has long, narrow, strap-like leaves, and it can form dense, perennial stands in still or slowly moving waters.

This family gets its common name from the frog's-bit (Limnobium spongia). This plant is a herb of marshes and calm waters of lakes and ponds. The frog's-bit is monoecious and has broad leaves with a well-defined petiole.

Species of plants in this family are commonly used as ornamental vegetation in fresh-water aquaria, and they are widely sold in pets shops for this purpose. These plants may also be used in horticultural ponds.

Some species in the frog's bit family have been introduced beyond their native range and have become serious weeds of ponds, lakes, and canals. The Canadian water-weed (Hydrilla vertricillata) is a problem in North America. An Argentinean water-weed (Elodea densa) has also become a pest after being introduced to North America, probably as plants that were discarded from aquaria.

Bill Freedman

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