Potamogeton praelongus |
Potamogeton tennesseensis |
|
---|---|---|
long-stalk pondweed, potamot à longs pédoncules, white-stalk pondweed, white-stem pondweed |
Tennessee pondweed |
|
Cauline stems | terete, without spots, to 210 cm; nodal glands absent. |
terete, without spots, 10–35 cm; glands absent. |
Turions | absent. |
absent. |
Leaves | submersed, ± spirally arranged, sessile, lax; stipules persistent, conspicuous, convolute, free from blade, white to green, not ligulate, 3–8.1 cm, fibrous, shredding at apex; blade pale green, rarely olive green, linear-lanceolate, not arcuate, 0.8–2.8 cm × 11–46 mm, base clasping, without basal lobes, margins entire, rarely crispate, apex hoodlike, splitting when pressed, obtuse, lacunae absent; veins 11–33. |
both submersed and floating or floating absent, ± spirally arranged. |
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 | emersed, unbranched; peduncles not dimorphic, terminal or axillary, erect to spreading, cylindric, 9.5–53 cm; spikes not dimorphic, cylindric, 34–75 mm. |
unbranched, emersed; peduncle not dimorphic, axillary, ascending, cylindric, 3–8 cm; spikes not dimorphic, cylindric, 10–22 mm. |
Fruits | sessile, greenish brown, obovoid, turgid, abaxially keeled, occasionally laterally keeled, 4–5.7 × 3.2–4 mm, lateral keels when present without points; beak erect, 0.6–1 mm; sides without basal tubercles; embryo with 1 full spiral. |
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. |
Rhizome(s) | present. |
present. |
2n | = 52. |
|
Potamogeton praelongus |
Potamogeton tennesseensis |
|
Phenology | Flowering summer–fall. | Flowering mid spring–fall. |
Habitat | Neutral to alkaline waters of lakes, rivers, and streams | Slow- to fast-moving streams and rivers |
Elevation | Greenland; 100–3000 m (Greenland; 300–9800 ft) | 200–1000 m (700–3300 ft) |
Distribution |
AK; CA; CO; CT; IA; ID; IN; MA; ME; MI; MN; MT; NE; NH; NJ; NY; OR; PA; SD; UT; VT; WI; WY; AB; BC; MB; NB; NF; NS; NT; NU; ON; PE; QC; SK; YT; Mexico; Greenland; Eurasia
|
KY; MD; NC; OH; PA; TN; VA; WV |
Discussion | Potamogeton praelongus is one of the easiest pondweeds to identify with its submersed leaves only clasping the more or less zigzagged stem. The persistent, hugelarge, white stipules provide another clue to this species. Four hybrids, Potamogeton perfoliatus × P. praelongus (= P. × cognatus Ascherson & Graebner), P. alpinus × P. praelongus (= P. × griffithii A. Bennett), P. crispus × P. praelongus (= P. × undulatus Wolfgang ex Schultes & Schultes f.), and P. gramineus × P. praelongus (= P. × vilnensis Galinus), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | Potamogetonaceae > Potamogeton | Potamogetonaceae > Potamogeton |
Sibling taxa | ||
Name authority | Wulfen: Arch. Bot. (Leipzig) 3: 331. (1805) | Fernald: Rhodora 38: 167, plate 412. (1936) |
Web links |
|