Northern Prairie Wildlife Research Center
Aquatic and Wetland Vascular Plants of the Northern Great Plains
Elodea Michx. -- Waterweed
Stems slender, lax to rather rigid and brittle, sparingly to freely branched,
rooting from the lower nodes or sometimes free-floating. Leaves sessile,
crowded toward the apex, mostly in whorls of 3(4) or opposite and decussate,
the margins finely serrulate. Flowers minute, delicate, often lost in
collection, solitary in the upper leaf axils, subtended by a 2-lobed spathe,
usually extended to the water surface by a long, threadlike hypanthium or (in
male flowers of E. nuttallii) sessile and breaking free to float to the
surface; sepals 3; petals 3 or seldom absent; male flowers
containing 9 stamens; female flowers with 3 staminodes and 3 stigma lobes
protruding at the summit of the hypanthium, the stigmas entire or 2-lobed. Fruit
ovoid to cylindric, several-seeded.
St. John, H. 1965. Monograph of the genus Elodea. Part 4: The
species of the eastern and central North America. Rhodora 67:1-35,
||Middle and upper leaves in whorls of 3(4).
||Middle and upper leaves decussate.
||Leaves mostly (1)1.5-3(5) mm wide, obtuse-apiculate
at the apex; male flowers extended to the surface by a long, threadlike
hypanthium; sepals of female flowers 2-3 mm long.
||Leaves (0.3)0.7-1.5 mm wide, acute or acute-apiculate
at the apex; male flowers sessile inside the spathe, breaking free to
float to the surface at anthesis; sepals of female flowers ca. 1 mm
52. Hydrocharitaceae, the Frog's-bit Family
1. Elodea Michx. -- Waterweed
- 1. Elodea canadensis L. C. Rich. in
- 2. Elodea longivaginata St. John
- 3. Elodea nuttallii (Planch.) St.
Return to Family -- Hydrocharitaceae - The Frog's-bit
Return to Contents