Potamogeton confervoides |
Potamogeton amplifolius |
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alga pondweed, alga-like pondweed, potamot confervoide, Tuckerman's pondweed |
big-leaf pondweed, broad-leaf pondweed, large-leaf pondweed, potamot à grandes feuilles |
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Rhizomes | obvious. |
present. |
Cauline stems | terete, without spots, 10–80 cm. |
terete, often rusty spotted, 6–110 cm; nodal glands absent. |
Turions | present, in axils of old leaves and from disintegrating branches, fusiform, 0.7–2 cm, leaves spreading to ascending. |
absent. |
Leaves | submersed, ± spirally arranged, flaccid, sessile; stipules deliquescent, inconspicuous, convolute, free from blade, pale green, not ligulate, 0.5–1.2 cm, not fibrous, not shredding at tip, apex obtuse; blade pale green, linear, not arcuate, 1.8–6.5 cm × 0.1–0.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, extremely attenuate, bristly, lacunae present, each side of midvein to margins; veins 1. |
both submersed and floating or floating absent, ± spirally arranged. |
Floating leaves | petioles continuous in color to apex, 2.3–22.6 cm; blade adaxially light green, lanceolate to round elliptic, 4.3–9.2 cm × 25–38 mcm, base rounded to cordate, apex acute to rounded; veins 27–49. |
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Submersed leaves | petiolate, lax; stipules persistent, conspicuous, convolute, free from blade, light brown, not ligulate, 1.5–11.7 cm, not fibrous, not shredding at tip, apex acute; petioles terete, 0.9–11.5 cm; blade light to dark green, ovate to oblanceolate, distinctly arcuate, 5–12.5 cm × 15–58 mm, base rounded to acute, without basal lobes, not clasping, margins entire, crispate, apex not hoodlike, acute to round-apiculate, lacunae absent; veins 19–49. |
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Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal, ascending, somewhat clavate, (3–)5–25 cm; spikes not dimorphic, capitate, 5–12 mm. |
unbranched, emersed; peduncles not dimorphic, terminal or axillary, erect, cylindric, 4.5–22.3 cm; spikes not dimorphic, cylindric, 34–65 mm. |
Fruits | sessile, light green, round-obovoid or nearly orbicular, compressed, abaxially and laterally keeled, 2–3 × 1.7–2.8 mm, lateral keels without sharp point; beak erect, 0.5 mm; sides without basal tubercles; embryo with less than 1 full spiral. |
sessile, reddish brown, obovoid, turgid, abaxially keeled, laterally ridged, 5–6.7 × 4.5–5.2 mm, lateral ridges without points; beak erect, 0.5–0.8 mm; sides without basal tubercles; embryo with full spiral. |
Chromosome number | apparently unknown not available. |
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2n | = 52. |
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Potamogeton confervoides |
Potamogeton amplifolius |
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Phenology | Flowering early–late summer. | Flowering summer–fall. |
Habitat | Acidic waters of bogs, ponds, and lakes, often at higher elevation in e portion of range | Waters of lakes, ponds, streams, and rivers |
Elevation | 0–1500 m (0–4900 ft) | 0–1900(–2900) m (0–6200(–9500) ft) |
Distribution |
CT; MA; ME; MI; NC; NH; NJ; NY; PA; RI; SC; VT; WI; NB; NL; NS; ON; QC; SPM; St Pierre
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AL; AR; CA; CT; GA; IA; ID; IL; IN; KS; MA; MD; ME; MI; MN; MO; MT; NC; NE; NH; NJ; NY; OH; OK; OR; PA; RI; SD; TN; VA; VT; WA; WI; WV; WY; BC; MB; NB; NF; NS; ON; QC; SK
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Discussion | Potamogeton confervoides is most uncommon and found only in fairly acidic waters. It is easily recognized by its linear, bristly leaves and the unusually long peduncle that seems out of place on a plant with such fine leaves. The leaves are so fine that they almost appear as greenish colored hair in the water. When the plant is removed from the water, the leaves are extremely flaccid leaves and essentially collapse onto each other. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
No specimens have been seen from Kentucky or Texas, but the species is to be expected there. Potamogeton amplifolius is common throughout much of North America. Its submersed leaves are larger than those of most other species of Potamogeton, are arcuate, and have more veins than do any other species. One hybrid, Potamogeton amplifolius × P. illinoensis (= P. × scoliophyllus Hagström), has been described. (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 | ||
Synonyms | P. tuckermanii | |
Name authority | Reichenbach: in H. G. L. Reichenbach et al., Icones florae germanicae et helveticae 7: 13. (1845) | Tuckerman: American Journal of Science, and Arts ser. 2, 6:225. (1848) |
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