Potamogeton praelongus |
Potamogeton diversifolius |
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long-stalk pondweed, potamot à longs pédoncules, white-stalk pondweed, white-stem pondweed |
diverse-leaf pondweed, Rafinesque's pondweed, water-thread pondweed |
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Cauline stems | terete, without spots, to 210 cm; nodal glands absent. |
compressed, 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, 0.7–0.8 cm; blade adaxially light green, obovate to elliptic, 0.8–1.6 cm × 3–8.5 mm, base acute, apex round to acute; veins 3–7. |
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Submersed leaves | sessile, lax; stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade ½ stipule length, light brown to red-brown, ligulate, 1.5–2.3 cm, not fibrous, not shredding at tip, apex obtuse; blade red-brown to light green, linear, often arcuate, 1–1.3 cm × 0.1 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, lacunae present, 1–2 rows each side midrib; veins 1. |
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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; peduncles dimorphic, submersed axillary, recurved, clavate, 3–5 mm, emersed axillary or terminal, erect to slightly recurved, clavate, 6–15 mm; spikes dimorphic, submersed capitate, 2–3 mm, emersed cylindric, 5–9.7 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, orbicular, compressed, abaxially winged, laterally winged, 1–1.5 × 0.9–2 mm, lateral wings with sharp points; beak present, erect, 0.1 mm; sides without basal tubercles; embryo with more than 1 full spiral. |
Rhizome(s) | present. |
present. |
2n | = 52. |
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Potamogeton praelongus |
Potamogeton diversifolius |
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Phenology | Flowering summer–fall. | Flowering and fruiting spring–fall. |
Habitat | Neutral to alkaline waters of lakes, rivers, and streams | Ponds, lakes, streams, and rivers |
Elevation | Greenland; 100–3000 m (Greenland; 300–9800 ft) | 5–2500 m (0–8200 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
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AL; AR; AZ; CA; CO; CT; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; MN; MO; MS; MT; NC; ND; NE; NJ; NV; NY; OH; OK; OR; PA; SC; SD; TN; TX; VA; VT; WI; WV; Mexico; Wyo
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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.) |
Potamogeton diversfolius is very likely the most common species of Potamogeton the genus in the southeastern United States. It has been separated into two species, P. diversifolius in the strict sense and P. capillaceus (M. L. Fernald 1932). The species has also been divided into two varieties, var. diversifolius and var. trichophyllous Morong (D. O S. Correll and M. C. Johnston 1970) . Potamogeton diversifolius var. trichophyllous actually is misapplied, as the name really refers to the more northern P. bicupulatus Fernald. We are following E. J. Klekowski Jr. and E. O. Beal (1965) in accepting only one taxon, as we have studied the species over much of its range and reached similar conclusions. (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. capillaceus | |
Name authority | Wulfen: Arch. Bot. (Leipzig) 3: 331. (1805) | Rafinesque: Medical Repository hexade 2, 5:354. (1808) |
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