Potamogeton bicupulatus |
Potamogeton perfoliatus |
|
---|---|---|
snail-seed pondweed |
clasping-leaf pondweed, potamot perfolié |
|
Rhizomes | present. |
present. |
Cauline stems | compressed, without spots, 10–25 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, 5–35 mm; blade adaxially light green, lanceolate-elliptic to broadly elliptic, 0.6–2.3(–2.8) cm × 1–11 mm, base tapering or rounded, apex acute to long tapering; veins 3–7. |
|
Submersed leaves | sessile, lax; stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade for less than ½ stipule length, light green, ligulate, 0.2–1.2 cm, not fibrous, not shredding at tip, apex obtuse; blade light green to rarely brown, linear-setaceous, not arcuate, 1.5–11 cm × 0.1–0.4(–0.6) mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, tapering, lacunae absent; veins 1. |
|
Inflorescences | unbranched; peduncles dimorphic, submersed axillary, somewhat recurved, clavate, 1–10 mm, emersed axillary or terminal, erect to slightly recurved, slightly clavate, 3.5–22 mm; spikes dimorphic, submersed, globular to ellipsoid, 1.5–7 mm, emersed ellipsoid to cylindric, 3–14 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, somewhat orbicular, compressed, abaxially keeled, laterally keeled, 1.1–2.1 × 1.1–2 mm, lateral keel without points; beak absent; sides without basal tubercles; embryo with more 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 bicupulatus |
Potamogeton perfoliatus |
|
Phenology | Flowering early summer–fall. | Flowering summer–fall. |
Habitat | Acidic waters of ponds, lakes, and streams | Waters, often brackish, of lakes, streams, rivers, and bays |
Elevation | 0–300 m (0–1000 ft) | 0–100 m (0–300 ft) |
Distribution |
CT; DE; IN; MA; ME; MI; NH; NY; PA; RI; TN; VA; VT; WI; ON
|
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 | Potamogeton bicupulatus is an uncommon species of the acid lakes and streams of northeastern United States and southern Canada. It is the final third species we have with dimorphic inflorescences and embryos with more than one full spiral. It can be separated from the other two, Potamogeton spirillus and P. diversifolius, because it has very narrow submersed leaves without lacunae and fruits with lateral keels without sharp points. (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 | Potamogetonaceae > Potamogeton | Potamogetonaceae > Potamogeton |
Sibling taxa | ||
Synonyms | P. diversifolius var. trichophyllus | |
Name authority | Fernald: Memoirs of the american academy of arts and science 17: 112. (1932) | Linnaeus: Sp. Pl. 1: 126. 1753 (as perfoliatum) |
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