Potamogeton tennesseensis |
Potamogeton perfoliatus |
|
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Tennessee pondweed |
clasping-leaf pondweed, potamot perfolié |
|
Rhizomes | present. |
present. |
Cauline stems | terete, without spots, 10–35 cm; glands absent. |
terete, without spots, to 250 cm; nodal glands absent. |
Turions | absent. |
absent. |
Leaves | both submersed and floating or floating absent, ± spirally arranged. |
submersed, ± spirally arranged, sessile, lax; stipules deteriorating into fibers and deciduous, inconspicuous (absent on proximal portion of stem), convolute, free from blade, light brown to green, not ligulate, 3.5–6.5 cm, not fibrous, not shredding at apex; blade olive-green, broadly lanceolate, orbiculate, or ovate, not arcuate, 0.9–7.6(–9.7) cm × 7–40 mm, base rounded, without basal lobes, clasping, margins entire, often crispate, apex not hoodlike, not splitting when pressed, round, rarely acute; veins 3–25. |
Floating leaves | petiolate; petioles continuous in color to apex, 2.5–6 cm; blade greenish brown adaxially, lance-oblong, 2–4(–5.5) cm × 5–13 mm, base acute, apex acute; veins 9–23. |
|
Submersed leaves | sessile, lax; stipules persistent, inconspicuous, convolute, adnate to blade for ¼ or less stipule length, light brown to dark green, ligulate, 0.5–1.5 cm, not fibrous, not shredding at tip, apex acute; blade red-brown to dark green, linear-filiform, not arcuate, 2.5–10.5 cm × 0.2–1(–2) mm, base slightly tapering, not clasping, without basal lobes, margins entire, not crispate, apex not hoodlike, long tapering, lacunae abundant, broad, filling area between margin and midvein; veins 1–3. |
|
Inflorescences | unbranched, emersed; peduncle not dimorphic, axillary, ascending, cylindric, 3–8 cm; spikes not dimorphic, cylindric, 10–22 mm. |
unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect to rarely recurved, cylindric, 1–7.3 cm; spike not dimorphic, cylindric, 0.4–4.8 cm. |
Fruits | sessile, greenish brown, quadrate-orbicular, slightly compressed, abaxially keeled, laterally ridged, 2.5–3 × 2–2.5 mm; lateral ridges without points; beak present, erect, 0.5 mm; sides without basal tubercles; embryo with less than 1 full spiral. |
sessile, greenish brown to olive-green, obovoid, turgid or rarely concave, not abaxially or laterally keeled, 1.6–3 × 1.3–2.2 mm; beak erect, 0.4–0.6 mm; sides without basal tubercles; embryo with 1 full spiral. |
2n | = 52. |
|
Potamogeton tennesseensis |
Potamogeton perfoliatus |
|
Phenology | Flowering mid spring–fall. | Flowering summer–fall. |
Habitat | Slow- to fast-moving streams and rivers | Waters, often brackish, of lakes, streams, rivers, and bays |
Elevation | 200–1000 m (700–3300 ft) | 0–100 m (0–300 ft) |
Distribution |
KY; MD; NC; OH; PA; TN; VA; WV |
AL; CT; DC; DE; FL; LA; MA; MD; ME; NC; NH; NJ; NY; OH; PA; RI; VA; VT; NB; NL; NS; ON; PE; QC; SPM; Africa; Greenland; Eurasia; Central America (Guatemala); Australia
|
Discussion | No specimens have been seen from Maryland although the species is to be expected there. Of conservation concern. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. perfoliatus × P. pusillus (= P. × mysticus Morong), P. gramineus × P. perfoliatus (= P. × nitens Weber [P. × subnitens Hagström]), and P. alpinus × P. perfoliatus (= P. × prussicus Hagström), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | ||
Sibling taxa | ||
Name authority | Fernald: Rhodora 38: 167, plate 412. (1936) | Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum) |
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