Potamogeton ogdenii |
Potamogeton oakesianus |
|
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Ogden's pondweed, potamot d'Ogden |
Oakes' pondweed, potamot d'Oakes |
|
Rhizomes | absent. |
present. |
Cauline stems | compressed-filiform, without spots, to 50 cm; glands green, golden brown to dark brown, 0.2–0.6 mm diam. |
terete, with red spots, 7–75 cm; nodal glands absent. |
Turions | terminal or lateral, uncommon, 3.7–9.9 × 2.6–6 cm, soft to hard; leaves flattened with outer and inner leaves in same plane; outer leaves 1–2 per side, base not corrugate, apex apiculate; inner leaves undifferentiated or rolled into hardened, fusiform structure. |
absent. |
Leaves | submersed, ± spirally arranged, sessile, rigid; stipules persistent, inconspicuous, convolute, free from blade, brown or rarely white, not ligulate, 0.9–2.1 cm, slightly fibrous, partially shredding at tip, apex obtuse; blade somewhat reddish to olive-green, linear, not arcuate, 1.5–10 cm × 1.2–2.9 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, cuspidate to bristle-tipped, lacunae present or absent, in 0–3 rows each side of midvein; veins 3–9(–13). |
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 occasionally axillary, erect or rarely recurved, slightly clavate, 1–3 cm; spikes not dimorphic, cylindric, 5–11 mm. |
unbranched, emersed; peduncles not dimorphic, terminal, ascending to spreading, cylindric, 2.5–8 cm; spikes not dimorphic, cylindric, 10–35 mm. |
Fruits | sessile, dark green, orbicular, turgid, abaxial keel obscure, lateral keels obscure or absent, 2.5–3 × 2.2–3 mm, lateral keels if present without points; beak erect, 0.5 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 | unknownnot available. |
apparently unknown. |
Potamogeton ogdenii |
Potamogeton oakesianus |
|
Phenology | Flowering mid summer–fall. | Flowering summer–fall. |
Habitat | Alkaline waters of ponds and lakes | Quiet acidic waters of bogs, ponds, and lakes |
Elevation | 100–300 m (300–1000 ft) | 50–1500 m (200–4900 ft) |
Distribution |
CT; MA; NY; VT; ON |
CT; MA; ME; MI; MN; MT; NH; NJ; NY; PA; RI; VA; VT; WI; WV; BC; NB; NL; NS; ON; QC; SPM
|
Discussion | Potamogeton ogdenii is an extremely local species, probably known from fewer than a dozen localities. The species is herein reported for the first time from Canada, being known from that country by a single collection made in 1987. Of conservation concern. (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 | ||
Sibling taxa | ||
Name authority | Hellquist & R. L. Hilton: Systematic Botany 8: 88, figs. 1–3, plates 1–2, figs. 1–3. (1983) | J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867) |
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