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Najas
See list of 4 species in this genusReferences: Hellquist and Crow (1980), Haynes (2000c).
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1a. Each margin of the leaf blade with 7–17 spinules [Fig. 131], these either minute and unicellular or larger and multicellular; apex of leaf sheath truncate or auriculate [Fig. 131]
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2a. Axis of seeds curved; style situated at center of seed apex; leaf blades usually recurved in age, the margins with multicellular teeth that are often visible to the unaided eye; staminate flowers 1.9–2.2 mm long
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2b. Axis of seeds straight; style situated off to one side of seed apex; leaf blades ascending to spreading, the margins with minute, unicellular teeth that usually require magnification to resolve; staminate flowers 1.5–2 mm long
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1b. Each margin of the leaf blade with 18–100 minute, unicellular spinules; apex of leaf sheath convexly tapering into base of blade (rarely truncate in N. guadalupensis)
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3a. Testa of seeds dull, minutely pitted and appearing so even at low magnification; seeds fusiform, widest at the middle; anthers 4-locular (rarely 1-locular); leaves 0.2–2.1 mm wide
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3b. Testa of seeds glossy, very minutely pitted and appearing ± smooth at low magnification; seeds narrow-obovoid to broad-obovoid, widest above the middle; anthers 1-locular; leaves 0.2–0.6 mm wide
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Each photo represents one species in this genus.