Northern Prairie Wildlife Research Center


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Aquatic and Wetland Vascular Plants of the Northern Great Plains

52. Hydrocharitaceae, the Frog's-bit Family

1. Elodea Michx. -- Waterweed

3. Elodea nuttallii (Planch.) St. John

Similar to E. canadensis but smaller and more delicate, the stems slender, terete, often freely branched. Lower leaves opposite and reduced, ovate-lanceolate; middle and upper leaves in whorls of 3 or occasionally 4, linear to linear-lanceolate, 6-13 mm long, (0.3)0.7-1.5 mm wide, acute or acute-apiculate at the apex. Spathes of male flowers borne in middle axils, sessile, ovoid, ca. 2 mm long, 2-parted but the lobes twisted together so that the spathe appears pointed; male flowers solitary and sessile in the spathe, breaking free and floating to the surface where the flower opens; sepals ovate, ca. 2 mm long, sometimes reddish; petals lacking or to 0.5 mm long, ovate-lanceolate; stamens 9, the inner 3 elevated on a common stalk. Spathes of female flowers borne in upper axils, narrowly cylindric but slightly broadened at the base and the bifid tip, 9-25 mm long; female flowers extended to the surface by a threadlike hypanthium to 9 cm long; sepals obovate, ca. 1 mm long; petals white, obovate, longer than the sepals; stigmas slender, shallowly bifid, slightly exceeding the sepals. Fruit narrowly ovoid to fusiform, 5-7 mm long; seeds cylindric, 3.5-4.5 mm long, pilose. Jun--Aug. Quiet water of streams and lakes; e and nc NE; (Que. to MN and NE, s to NC, MO, OK and NM; also ID). Anacharis occidentalis (Pursh) Victorin, A. nuttallii Planch.

Reports of this species for ND were based on misidentifications of E. canadensis. The same may be true for SD, even though E. nuttallii is perhaps to be expected in the se part of the state.

Previous Section -- Elodea longivaginata St. John
Return to Family -- Hydrocharitaceae - The Frog's-bit Family
Next Section -- Vallisneria americana Michx.

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