Potamogeton friesii |
Potamogeton oakesianus |
|
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flat-stalk pondweed, Fries' pondweed, potamot de Fries |
Oakes' pondweed, potamot d'Oakes |
|
Rhizomes | absent. |
present. |
Cauline stems | compressed, without spots, 10–135 cm; glands green, greenish brown, or gold, to 0.7 mm diam. |
terete, with red spots, 7–75 cm; nodal glands absent. |
Turions | terminal or lateral, common, 1.5–5 cm × 1.5–4 mm, soft; leaves ± 4-ranked; outer leaves 2–3 per side, base corrugate, apex apiculate to acute; inner leaves reduced, arranged into fan-shaped structure and oriented at 90° angles to outer leaves. |
absent. |
Leaves | submersed, ± spirally arranged, delicate to rigid, sessile; stipules not persistent, inconspicuous, convolute, free from blade, white, not ligulate, 0.55–2.1 cm, fibrous, coarse, shredding at tip, apex obtuse; blade light green, rarely olive-green to.somewhat reddish, linear, not arcuate, 2.3–6.5 cm × 1.2–3.2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to apiculate, lacunae absent or 1 narrow row each side of midrib; veins 5–7(–9). |
both submersed and floating, ± spirally arranged. |
Floating leaves | petioles continuous in color to apex, 3.2–7.5 cm; blade adaxially light to dark green, lanceolate to elliptic or ovate, (1.5–)2–4(–5.5) cm × 10–20(–30) mm, base rounded or tapering, apex acute; veins (7–)9–19(–23). |
|
Submersed leaves | sessile, lax; stipules persistent, conspicuous, convolute, free from blade, whitish, not ligulate, 1–3 cm, delicately fibrous, not shredding at tip, apex obtuse; blade pale green, linear to phyllodial, not arcuate, 5–16 cm × (0.25–)0.3–1 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex acute, not hoodlike, lacunae absent, setaceous; veins 3. |
|
Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect or rarely recurved, slightly clavate, 1.2–4.1(–7) cm; spike not dimorphic, cylindric, 7–16 mm. |
unbranched, emersed; peduncles not dimorphic, terminal, ascending to spreading, cylindric, 2.5–8 cm; spikes not dimorphic, cylindric, 10–35 mm. |
Fruits | sessile, olive-green to brown, obovoid, turgid, not abaxially or laterally keeled, 1.8–2.5 × 1.2–2 mm; beak erect, 0.3–0.7 mm; sides without basal tubercles; embryo with 1 full spiral. |
sessile, greenish brown, obovoid, turgid, abaxially keeled, laterally keeled, 2.5–3.5(–3.7) × (1.6–)2–2.4 mm, lateral keels without points; beak erect, 0.4–0.8 mm; sides without basal tubercles; embryo with 1 full spiral. |
Chromosome number | apparently unknown. |
|
2n | = 26. |
|
Potamogeton friesii |
Potamogeton oakesianus |
|
Phenology | Flowering and fruiting summer–fall. | Flowering summer–fall. |
Habitat | Calcareous to brackish waters of lakes and slow-flowing streams | Quiet acidic waters of bogs, ponds, and lakes |
Elevation | 0–3100 m (0–10200 ft) | 50–1500 m (200–4900 ft) |
Distribution |
AK; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NY; OH; PA; RI; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NF; NS; NT; ON; PE; QC; SK; YT; Eurasia
|
CT; MA; ME; MI; MN; MT; NH; NJ; NY; PA; RI; VA; VT; WI; WV; BC; NB; NL; NS; ON; QC; SPM
|
Discussion | Potamogeton friesii is a fairly common linear-leaved species, especially of calcareous waters of lakes and streams of the upper Midwest. Whenever turions are present, the species is easily identified, as it is the only one with the outer leaves of the turions having corrugate bases and the inner leaves turned at right angles to the outer leaves. Two hybrids, Potamogeton friesii × P. pusillus (= P. × pusilliformis Fischer [P. × intermedius Fischer]) and P. friesii × P. obtusifolius (= P. × semifructus A. Bennett ex Ascherson & Graebner), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Potamogeton oakesianus, along with Potamogeton floridanus and P. natans, has floating leaves and phyllodial submersed leaves. The petioles of this species and of P. floridanus lack a short area of light-colored tissue immediately proximal to the blade. (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 | Ruprecht: Hist. Stirp. Fl. Petrop. 43. (1845) | J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867) |
Web links |