Potamogeton tennesseensis |
Potamogeton oakesianus |
|
---|---|---|
Tennessee pondweed |
Oakes' pondweed, potamot d'Oakes |
|
Rhizomes | present. |
present. |
Cauline stems | terete, without spots, 10–35 cm; glands absent. |
terete, with red spots, 7–75 cm; nodal glands absent. |
Turions | absent. |
absent. |
Leaves | both submersed and floating or floating absent, ± spirally arranged. |
both submersed and floating, ± 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. |
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, 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. |
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; peduncle not dimorphic, axillary, ascending, cylindric, 3–8 cm; spikes not dimorphic, cylindric, 10–22 mm. |
unbranched, emersed; peduncles not dimorphic, terminal, ascending to spreading, cylindric, 2.5–8 cm; spikes not dimorphic, cylindric, 10–35 mm. |
Fruits | 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. |
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. |
|
Potamogeton tennesseensis |
Potamogeton oakesianus |
|
Phenology | Flowering mid spring–fall. | Flowering summer–fall. |
Habitat | Slow- to fast-moving streams and rivers | Quiet acidic waters of bogs, ponds, and lakes |
Elevation | 200–1000 m (700–3300 ft) | 50–1500 m (200–4900 ft) |
Distribution |
KY; MD; NC; OH; PA; TN; VA; WV |
CT; MA; ME; MI; MN; MT; NH; NJ; NY; PA; RI; VA; VT; WI; WV; BC; NB; NL; NS; ON; QC; SPM
|
Discussion | 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.) |
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 | Fernald: Rhodora 38: 167, plate 412. (1936) | J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867) |
Web links |