Potamogeton perfoliatus |
Potamogeton spirillus |
|
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clasping-leaf pondweed, potamot perfolié |
northern snail-seed pondweed, potamot spirille, spiral pondweed |
|
Rhizomes | present. |
present. |
Cauline stems | terete, without spots, to 250 cm; nodal glands absent. |
compressed, without spots, 5–40 cm; glands absent. |
Turions | absent. |
absent. |
Leaves | 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. |
both submersed and floating or floating absent, ± spirally arranged. |
Floating leaves | petiolate; petioles continuous in color to apex, 5–25 mm; blade adaxially light green, oblong to obovate, 0.7–—3.5 cm × 2–13 mm, base tapered to rounded, apex obtuse, rounded; veins 5–15. |
|
Submersed leaves | sessile, lax; stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade for ½ stipule length, reddish brown to light green, ligulate, 2–12 mm, not fibrous, not shredding at tip, apex obtuse; blade red-brown to light green, linear, not arcuate, 0.8–8 cm × 0.5–2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse to acute, lacunae present, a broad band each side of midvein; veins 1–3. |
|
Inflorescences | 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. |
unbranched; peduncles dimorphic, submersed axillary, recurved, clavate, 0.5–3 mm, emersed axillary or terminal, erect to recurved, slightly clavate, 4–27 mm; spikes dimorphic, submersed capitate, 2–5 mm, emersed ellipsoid to cylindric, 4–13 mm. |
Fruits | 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. |
sessile, greenish brown, somewhat orbicular, compressed, abaxially winged, laterally winged, 4–13 × 1.3–2.4 mm, lateral wing with blunt tips; beak absent; sides without basal tubercles; embryo with more than 1 full spiral. |
2n | = 52. |
|
Potamogeton perfoliatus |
Potamogeton spirillus |
|
Phenology | Flowering summer–fall. | Flowering mid summer–late fall. |
Habitat | Waters, often brackish, of lakes, streams, rivers, and bays | Neutral to acidic waters of ponds, lakes, and streams |
Elevation | 0–100 m (0–300 ft) | 0–400 m (0–1300 ft) |
Distribution |
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
|
CT; IA; MA; ME; MI; MN; NE; NH; NJ; NY; OH; PA; RI; VT; WI; MB; NB; NF; NS; ON; PE; QC
|
Discussion | 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.) |
The This is the firstone of three Potamogeton species in the flora area with dimorphic inflorescences. It can be separated from the other two species because its submersed leaf blades have broad lacunae, extending nearly from the midvein to the margin, and its fruits have lateral wings with blunt points along it. along them. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | ||
Sibling taxa | ||
Name authority | Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum) | Tuckerman: American Journal of Science, and Arts ser. 2, 6:228. (1848) |
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