Stuckenia filiformis |
Stuckenia filiformis subsp. alpina |
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fineleaf pondweed, slender-leaf pondweed, thread-leaf false pondweed, thread-leaf pondweed, western pondweed |
fineleaf pondweed, potamot filiforme alpin, slender-leaf pondweed |
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Stems | freely branching proximally, sparsely branching distally, subterete, (10–)20–60(–100) cm. |
10–30 cm. |
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Leaves | length and width of those on main stem only slightly larger than those on branches; stipules with stipular sheaths often inflated on proximal portion of stem, 1–4(–9.5) cm, summit of midstem stipules tight to stem, ca. ± same width as stem, ligule 2–20 mm, distinct, especially on distal stipules; blade filiform or slenderly linear, 1–15 cm × 0.2–2(–3.7) mm, apex notched, blunt, or short-apiculate; veins 1–3. |
stipules persistent; those on proximal portion of stem tightly clasping or slightly enlarged, to 1 mm wide. |
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Inflorescences | peduncles terminal, erect, filiform to slender, 2–10(–15) cm; spikes cylindric to moniliform, 5–55 mm; verticels 2–6(–9). |
peduncles with flower and/or fruits adjacent or separated by less than 2 cm. |
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Fruits | dark brown, obovoid, 2–3 × 1.5–2.4 mm; beak inconspicuous. |
common. |
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2n | = 78. |
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Stuckenia filiformis |
Stuckenia filiformis subsp. alpina |
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Phenology | Flowering spring–early fall. | |||||||||
Habitat | Calcareous, saline, or brackish shallow to deep waters of ponds, lakes, streams, ditches, and coastal inshore waters | |||||||||
Elevation | 0–3280 m (0–10800 ft) | |||||||||
Distribution |
AK; AZ; CA; CO; IA; ID; ME; MI; MN; MT; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NS; NT; NU; ON; PE; QC; SK; YT; nearly worldwide
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AK; AZ; CA; CO; ID; ME; MI; MN; MT; ND; NE; NH; NJ; NM; NV; NY; OH; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Greenland; Asia |
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Discussion | Three distinct subspecies seemingly apparently occur in North America. They are separated mainly by the size of the plants and the peduncle characteristics. Stuckenia filiformis subsp. occidentalis typically grows in cold deep water, standing or with a strong current. This variety tends to become robust and is easily confused with Stuckenia vaginata and S. striata. Stuckenia filiformis subsp. alpina is a much smaller plant typically growing in standing waters. Stuckenia filiformis subsp. filiformis is restricted to the far north. In the intermountain region of western United States is a more robust form that is quite similar to S. filiformis subsp. alpina but although it has previously been recognized as Potamogeton [Stuckenia] filiformis var. macounii Morong (J. L. Reveal 1977b). Subspecies ca. 5 (3 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
No specimens have been seen from Maryland, but the subspecies is to be expected there. One hybrid, P. filiformis × P. pectinatus (= P. × suecicus K. Richter), with this species as a putative parent has been described under the genus Potamogeton. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 22. | FNA vol. 22. | ||||||||
Parent taxa | Potamogetonaceae > Stuckenia | Potamogetonaceae > Stuckenia > Stuckenia filiformis | ||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Synonyms | Potamogeton filiformis | Potamogeton marinus, Potamogeton borealis, Potamogeton filiformis var. alpinus, Potamogeton filiformis var. borealis, Potamogeton filiformis var. macounii, Potamogeton interior, Potamogeton marinus var. alpinus, Potamogeton marinus var. macounii | ||||||||
Name authority | (Persoon) Börner: Flora fur das deutsche Volk 713. (1912) | (Blytt) R. R. Haynes: Novon 8: 241. (1998) | ||||||||
Web links |