Potamogeton nodosus |
Potamogeton vaseyi |
|
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loddon's pondweed, long-leaf pondweed, pondweed, potamot noeuex |
potamot de Vasey, Vasey's pondweed |
|
Rhizomes | present. |
absent. |
Cauline stems | terete, without spots, to 100 cm; nodal glands absent. |
terete, without spots, 2–5 cm; glands absent. |
Turions | absent. |
common, axillary, 0.5–2 cm × 0.5–1.2 mm, soft; leaves ± 2-ranked; outer leaves 2–3 per side, base not corrugate, apex acute; inner leaves undifferentiated or rolled into tight, hardened structure. |
Leaves | both submersed and floating, or floating absent, ± spirally arranged. |
submersed, or both submersed and floating, ± spirally arranged. |
Floating leaves | petioles 3.5–26 cm; blade adaxially light green, lenticular to elliptic, 3–11 cm × 15–45 mm, base cuneate to rounded, apex acute to rounded; veins 9–21. |
petioles continuous in color to apex, 5–25 mm; blade adaxially greenish brown, elliptic, spatulate, or obovate, 0.6–1.5 cm × 3–8 mm, base acute, apex obtuse; veins 5–9. |
Submersed leaves | petiolate, lax; stipules persistent to deliquescent, conspicuous, convolute, free from blade, light brown, not ligulate, 3–9 cm, not fibrous, not shredding at tip, apex round to acute; petioles 2–13 cm; blade light to dark green, linear-lanceolate to lance-elliptic, not arcuate, 9–20 cm × 10–35 mm, base acute, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, without sharp awl-like tip, lacunae in 2–5 rows each side of midrib; veins 7–15. |
sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, green to brown, not ligulate, 0.4–1.2 cm, not fibrous, not shredding at tip, apex attenuate; blade light green, linear-filiform, not arcuate, 2–8 cm × 0.1–1 mm, bases slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to almost bristle-tipped, lacunae present, rarely absent, 0–2 rows each side of midvein; veins 1(–3). |
Inflorescences | unbranched, emersed; peduncles not dimorphic, terminal, erect to ascending, cylindric, 3–15 cm; spikes not dimorphic, cylindric, 20–70 mm. |
unbranched, emersed; peduncles not dimorphic, terminal, ascending in flower, recurved in fruit, cylindric, 5–30 mm; spikes not dimorphic, cylindric or moniliform, 6–8 mm. |
Fruits | sessile, red to reddish brown, obovoid, abaxially keeled, laterally ridged, 2.7–4.3 × 2.5–3 mm, keel well developed, lateral ridges with blunt to sharp tips; beak erect; sides without basal tubercles; embryo with 1 full spiral. |
sessile, green to brown, obliquely round-obovoid, compressed, abaxially keeled, not laterally keeled, 1.5–2.5 × 1.2–1.6 mm; beak erect, 0.3–0.5 mm; sides without basal tubercles; embryo with 1 full spiral. |
2n | = 52. |
= 28. |
Potamogeton nodosus |
Potamogeton vaseyi |
|
Phenology | Flowering summer–fall. | Flowering and fruiting summer–fall. |
Habitat | Clear to turbid waters of lakes, streams, rivers, and sloughs | Quiet waters of lakes, ponds, and rivers |
Elevation | 0–3300 m (0–10800 ft) | 50–500 m (200–1600 ft) |
Distribution |
AL; AR; AZ; CA; CO; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; SD; TN; TX; UT; VA; VT; WA; WI; WV; WY; AB; BC; NB; ON; QC; SK; Mexico; Central America; South America; West Indies; Eurasia
|
CT; IA; IL; IN; MA; ME; MI; MN; NH; NJ; NY; OH; PA; RI; VT; WI; NB; ON; QC
|
Discussion | Six hybrids, Potamogeton gramineus × P. nodosus (= P. × argutulus Hagström), P. illinoensis × P. nodosus (= P. × faxonii Morong), P. nodosus × P. richardsonii (= P. × rectifolius A. Bennett), P. natans × P. nodosus (= P. × schreberi Fischer [P. × perplexus A. Bennett]), P. alpinus × P. nodosus (= P. × subotusus Hagström), and P. epihydrus × P. nodosus (= P. × subsessilis Hagström), have been described. Potamogeton nodosus is a common floating-leaved species throughout much of the United States and southern Canada. When both submersed and floating leaves are present, it is very easily recognized by the petioles of the submersed leaves being longer than 5 cm. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
All of the original material of Potamogeton lateralis Morong, including the collection designated as the lectotype, has been studied (C. B. Hellquist et al. 1988). Every specimen, was a mixed collection of P. pusillus and P. vaseyi. Based on the results of the study, P. lateralis is taxonomically nomenclaturally invalid and should be rejected. Potamogeton vaseyi is an uncommon species that has submersed leaves very similar to P. pusillus subsp. gemmiparus. Floating leaves apparently are present only when the species is fertile, and the species often grows intermixed with that subspecies. Collections are consequently often a mixture of the two taxa. Also, sterile collections of either taxon can easily be mistaken for the other. (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 | Poiret: in J. Lamarck et al., Encyclopedie Methodique. Botanique... Supplement 4(2): 5354. (1816) | J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867) |
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