Potamogeton praelongus |
Potamogeton robbinsii |
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white-stalked pondweed, white-stemmed pondweed |
Robbins' pondweed |
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Stems | terete; to 210 cm; nodal glands absent. |
terete; to 100 cm; nodal glands absent. |
Leaves | submersed, sessile, attached at stem nodes, not attached to stipules; stipules 30– 81 mm, fibrous, shredding at tip; blades linear-lanceolate, 50–200 × 10–30 mm; base clasping but without basal lobes, rarely wavy; tip obtuse; veins 11–33. |
submersed, conspicuously 2-ranked, sessile; more or less sti?; blades attached to lower 25% of petiole; stipules ligulate, 0.5– 2 cm, fibrous, shredding at tip; tip obtuse; blades linear to lanceolate, 20–70(120) × 3–4(8) mm; base rounded, with basal lobes (auricles); margins minutely spinulose to serrulate; tip acute; lacunae absent; veins 20–60. |
Inflorescences | emersed; spikes cylindric, 34–75 mm; peduncles terminal or axillary; erect to spreading, 10–30 cm. |
often branched; peduncles axillary; erect, 30–50(70)mm; spikes moniliform, 7–20 mm. |
Fruits | sessile, obovoid; turgid, 4–5.7 × 3.2–4 mm; greenish brown, dorsally keeled, occasionally laterally keeled; beaks erect, 0.6–1 mm. |
stipitate, obliquely obovoid; turgid, 3–4(5) × 2(3.3)mm, brown, dorsally and laterally keeled; beaks erect, recurved at tip, 0.7–0.9 mm. |
Potamogeton praelongus |
Potamogeton robbinsii |
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Distribution | ||
Discussion | Neutral to alkaline waters of lakes and streams. 0–1900m. BW, Est. CA, ID; north to British Columbia, east to Newfoundland, south to Mexico; Eurasia. Native. This species hybridizes with P. alpinus, P. crispus and P. gramineus. |
Shallow to deep water of ponds, lakes and slow-flowing rivers. 50–2400 m. BW, Casc, WV. CA, ID, WA; north to AK, northeast to Nunavut, east to Prince Edward Island. Native. Potamogeton robbinsii is our only species with branched inflorescences and auriculate leaf blades. It flowers only rarely. |
Source | Flora of Oregon, volume 1, page 499 Nick Otting, Richard Brainerd, Barbara Wilson |
Flora of Oregon, volume 1, page 500 Nick Otting, Richard Brainerd, Barbara Wilson |
Sibling taxa | ||
Web links |
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