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Published In: Species Plantarum 2: 1015. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/23/2009)


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1. Najas L. (naiad, water nymph)

(Haynes, 1979)

Plants annual, monoecious (dioecious elsewhere). Stems diffuse, highly branching, rooting at the lower nodes. Leaves opposite or appearing whorled, filiform, the margins serrulate, sometimes obscurely so. Stipules fused to the leaf base, membranous, sheathing. Flowers 1–3 per leaf axil, minute, unisexual. Perianth reduced to 2 minute, membranous scales or usually absent in pistillate flowers. Staminate flowers with 1 stamen. Pistillate flowers with 1 pistil. Pistils with 1 locule and 1 short style that branches into 2–4 narrowly triangular branches. Fruits 1‑seeded, the outer coat very thin and more or less transparent, wearing away irregularly. Seeds narrowly elliptic to obovate, sometimes curved at the tip, the hard surface variously ornamented. Thirty‑five to 40 species, worldwide.

The species of Najas are important food for waterfowl, and the often dense mats formed by most species provide cover for young fish and other aquatic organisms.


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1 Seeds straight or nearly so, not curved at the tip (sometimes slightly curved in N. guadalupensis); leaf sheaths gradually broadened, not auriculate (3)
+ Seeds curved to 1 side at the tip; leaf sheaths abruptly broadened, auriculate (2)
2 (1) Leaves ascending to spreading, not becoming recurved, the teeth usually visible only with magnification; seed coats with 25–40 indistinct rows of more or less square, fine pits 2 Najas gracillima
+ Leaves becoming recurved in the growing season, the marginal teeth multicellular, usually readily visible without magnification; seed coats with 12–18 rows of dense, ladderlike pits that are short, broad, and rectangular 4 Najas minor
3 (1) Seeds 2.5–3.7 mm long, shiny, elliptic to narrowly obovate 1 Najas flexilis
+ Seeds 1.2–2.5 mm long, dull, narrowly fusiform 3 Najas guadalupensis
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