Potamogeton pusillus |
Potamogeton ogdenii |
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small pondweed |
Ogden's pondweed, potamot d'Ogden |
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Rhizomes | absent. |
absent. |
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Cauline stems | terete to slightly compressed, without spots, 18–150 cm; glands present on at least some nodes, green, gold, brown, or rarely white, to 0.5 mm diam. |
compressed-filiform, without spots, to 50 cm; glands green, golden brown to dark brown, 0.2–0.6 mm diam. |
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Turions | common, soft, lateral or terminal, 0.9–3.2 cm × 0.3–1.8 mm, soft; leaves ± 2-ranked; outer leaves 1–3 per side, base not corrugate, apex subulate to obtuse; inner leaves rolled into hardened fusiform structure. |
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. |
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Leaves | submersed, ± spirally arranged, sessile, delicate to coarse; stipules persistent, inconspicuous, connate or convolute, free from base of blade, brown to green or white, not ligulate, 0.31–0.92 cm, rarely appearing fibrous, not shredding at tip, apex obtuse; blade pale green to olive-green, rarely somewhat reddish, linear, not arcuate, 0.9–6.5 cm × 0.2–2.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, subulate to obtuse, lacunae absent or present, in 0–5 rows each side of midrib; veins 1–3(–5). |
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). |
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Inflorescences | unbranched, submersed or emersed; peduncles not dimorphic, axillary or terminal, erect, rarely recurved, filiform to slightly clavate, 0.5–6.2(–6.6) cm; spikes not dimorphic, capitate to cylindric, 1.5–10.1 mm. |
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. |
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Fruits | sessile, green to brown, ovoid to obovoid, turgid to concave, not abaxially or laterally keeled, 1.5–2.2 × 1.2–1.6 mm; beak erect, 0.1–0.6; sides without basal tubercles; embryo with less than 1 full spiral. |
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. |
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Chromosome number | unknownnot available. |
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Potamogeton pusillus |
Potamogeton ogdenii |
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Phenology | Flowering mid summer–fall. | |||||||||
Habitat | Alkaline waters of ponds and lakes | |||||||||
Elevation | 100–300 m [300–1000 ft] | |||||||||
Distribution |
AK; 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; MB; NB; NS; NT; NU; ON; PE; QC; SK; YT; nearly worldwide
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CT; MA; NY; VT; ON |
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Discussion | Three hybrids, Potamogeton perfoliatus × P. pusillus (= P. × mysticus Morong), P. friesii × P. pusillus (= P. × pusilliformis Fisher [P. × intermedius Fischer]), and P. obtusifolius × P. pusillus (= P. × saxonicus Hagström), have been described. Subspecies 3 (3 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
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Key |
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Source | FNA vol. 22. | FNA vol. 22. | ||||||||
Parent taxa | ||||||||||
Sibling taxa | ||||||||||
Subordinate taxa | ||||||||||
Name authority | Linnaeus: Sp. Pl. 1: 127. 1753 (as pusillum) | Hellquist & R. L. Hilton: Systematic Botany 8: 88, figs. 1–3, plates 1–2, figs. 1–3. (1983) | ||||||||
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