Potamogeton tennesseensis |
Potamogeton spirillus |
|
---|---|---|
Tennessee pondweed |
northern snail-seed pondweed, potamot spirille, spiral pondweed |
|
Rhizomes | present. |
present. |
Cauline stems | terete, without spots, 10–35 cm; glands absent. |
compressed, without spots, 5–40 cm; glands absent. |
Turions | absent. |
absent. |
Leaves | both submersed and floating or floating absent, ± spirally arranged. |
both submersed and floating or floating absent, ± 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. |
petiolate; petioles continuous in color to apex, 5–25 mm; blade adaxially light green, oblong to obovate, 0.7–—3.5 cm × 2–13 mm, base tapered to rounded, apex obtuse, rounded; veins 5–15. |
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 to deliquescent, inconspicuous, convolute, adnate to blade for ½ stipule length, reddish brown to light green, ligulate, 2–12 mm, not fibrous, not shredding at tip, apex obtuse; blade red-brown to light green, linear, not arcuate, 0.8–8 cm × 0.5–2 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, obtuse to acute, lacunae present, a broad band each side of midvein; veins 1–3. |
Inflorescences | unbranched, emersed; peduncle not dimorphic, axillary, ascending, cylindric, 3–8 cm; spikes not dimorphic, cylindric, 10–22 mm. |
unbranched; peduncles dimorphic, submersed axillary, recurved, clavate, 0.5–3 mm, emersed axillary or terminal, erect to recurved, slightly clavate, 4–27 mm; spikes dimorphic, submersed capitate, 2–5 mm, emersed ellipsoid to cylindric, 4–13 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, somewhat orbicular, compressed, abaxially winged, laterally winged, 4–13 × 1.3–2.4 mm, lateral wing with blunt tips; beak absent; sides without basal tubercles; embryo with more than 1 full spiral. |
Potamogeton tennesseensis |
Potamogeton spirillus |
|
Phenology | Flowering mid spring–fall. | Flowering mid summer–late fall. |
Habitat | Slow- to fast-moving streams and rivers | Neutral to acidic waters of ponds, lakes, and streams |
Elevation | 200–1000 m (700–3300 ft) | 0–400 m (0–1300 ft) |
Distribution |
KY; MD; NC; OH; PA; TN; VA; WV |
CT; IA; MA; ME; MI; MN; NE; NH; NJ; NY; OH; PA; RI; VT; WI; MB; NB; NF; NS; ON; PE; QC
|
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.) |
The This is the firstone of three Potamogeton species in the flora area with dimorphic inflorescences. It can be separated from the other two species because its submersed leaf blades have broad lacunae, extending nearly from the midvein to the margin, and its fruits have lateral wings with blunt points along it. along them. (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) | Tuckerman: American Journal of Science, and Arts ser. 2, 6:228. (1848) |
Web links |