Potamogeton praelongus |
Potamogeton clystocarpus |
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long-stalk pondweed, potamot à longs pédoncules, white-stalk pondweed, white-stem pondweed |
little aguja pondweed |
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Cauline stems | terete, without spots, to 210 cm; nodal glands absent. |
terete to slightly compressed, without spots, to 57 cm; glands white to gold, 0.2–0.3 mm diam. |
Turions | absent. |
unknown. |
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. |
submersed, ± spirally arranged, sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, brown, not ligulate, to 0.62 cm, not fibrous, not shredding at tip, apex obtuse; blade green, linear, not arcuate, 3.2–7.8 cm × 0.7–1.7 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, lacunae rarely absent, in 0–4 rows each side of midrib; veins 3(–5). |
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; peduncles not dimorphic, axillary or terminal, erect, cylindric, 3.2–4.8 cm; spike not dimorphic, capitate to cylindric, 5.5–7.5 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, brown to yellow-green, obovoid, compressed, abaxially and laterally keeled, 2–2.2 × 1.7–1.8 mm, lateral keels without points; beak erect, 0.5–0.6 mm; sides with 1–3 tubercules near base; embryo with 1 full spiral. |
Rhizome(s) | present. |
absent. |
2n | = 52. |
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Potamogeton praelongus |
Potamogeton clystocarpus |
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Phenology | Flowering summer–fall. | Flowering and fruiting spring–summer. |
Habitat | Neutral to alkaline waters of lakes, rivers, and streams | Small streams |
Elevation | Greenland; 100–3000 m (Greenland; 300–9800 ft) | ca. 1800 m (ca. 5900 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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TX |
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 clystocarpus is an extremely limited species known from only one canyon in west Texas. 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: Memoirs of the american academy of arts and science n.s. 17:79, plates 15, 30, fig. 5. (1932) |
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