Potamogeton diversifolius |
Potamogeton hillii |
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diverse-leaf pondweed, Rafinesque's pondweed, water-thread pondweed |
Hill's pondweed |
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Rhizomes | present. |
absent. |
Cauline stems | compressed, without spots, 10–35 cm; glands absent. |
slightly compressed, without spots, 30–60 cm; glands rare, when present, brown to green, 0.1–0.3 mm diam. |
Turions | absent. |
terminal, rare, 2.8–3 cm × 1.5–3 mm, soft; leaves ± 2-ranked; outer leaves 3–4 per side, base not corrugate, apex acute to apiculate; inner leaves undifferentiated. |
Leaves | both submersed and floating or floating absent, ± spirally arranged. |
submersed, ± spirally arranged, sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, white to light brown, not ligulate, 0.7–1.6 cm, slightly fibrous, rarely shredding at tip, apex obtuse; blade pale green to olive-green, linear, not arcuate, 2–6 cm × 0.6–2.5(–4) mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, apiculate to bristle-tipped or rarely blunt, lacunae in 1–2 rows each side of midrib; veins 3. |
Floating leaves | petiolate; petioles continuous in color to apex, 0.7–0.8 cm; blade adaxially light green, obovate to elliptic, 0.8–1.6 cm × 3–8.5 mm, base acute, apex round to acute; veins 3–7. |
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Submersed leaves | sessile, lax; stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade ½ stipule length, light brown to red-brown, ligulate, 1.5–2.3 cm, not fibrous, not shredding at tip, apex obtuse; blade red-brown to light green, linear, often arcuate, 1–1.3 cm × 0.1 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, lacunae present, 1–2 rows each side midrib; veins 1. |
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Inflorescences | unbranched; peduncles dimorphic, submersed axillary, recurved, clavate, 3–5 mm, emersed axillary or terminal, erect to slightly recurved, clavate, 6–15 mm; spikes dimorphic, submersed capitate, 2–3 mm, emersed cylindric, 5–9.7 mm. |
unbranched, emersed; peduncles not dimorphic, axillary and/or terminal, erect to ascending, rarely recurved, slightly clavate, 6–13.5 mm; spikes not dimorphic, globose, (2–) 4–7 mm. |
Fruits | sessile, greenish brown, orbicular, compressed, abaxially winged, laterally winged, 1–1.5 × 0.9–2 mm, lateral wings with sharp points; beak present, erect, 0.1 mm; sides without basal tubercles; embryo with more than 1 full spiral. |
brown to light greenish brown, ovoid to orbicular, turgid, sessile, abaxially and laterally keeled (3-keeled), 2.3–4 × 2–3.2 mm, lateral keels without points; beak erect, 0.3–0.7 mm; sides without basal tubercles; embryo with 1 full spiral. |
Chromosome number | unknownnot available. |
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Potamogeton diversifolius |
Potamogeton hillii |
|
Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting summer. |
Habitat | Ponds, lakes, streams, and rivers | Alkaline waters of marshes, ponds, lakes, and slow-moving streams |
Elevation | 5–2500 m (0–8200 ft) | 50–400 m (200–1300 ft) |
Distribution |
AL; AR; AZ; CA; CO; CT; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; MN; MO; MS; MT; NC; ND; NE; NJ; NV; NY; OH; OK; OR; PA; SC; SD; TN; TX; VA; VT; WI; WV; Mexico; Wyo
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CT; MA; MI; NY; OH; PA; VA; VT; WI; ON
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Discussion | Potamogeton diversfolius is very likely the most common species of Potamogeton the genus in the southeastern United States. It has been separated into two species, P. diversifolius in the strict sense and P. capillaceus (M. L. Fernald 1932). The species has also been divided into two varieties, var. diversifolius and var. trichophyllous Morong (D. O S. Correll and M. C. Johnston 1970) . Potamogeton diversifolius var. trichophyllous actually is misapplied, as the name really refers to the more northern P. bicupulatus Fernald. We are following E. J. Klekowski Jr. and E. O. Beal (1965) in accepting only one taxon, as we have studied the species over much of its range and reached similar conclusions. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Potamogeton hillii is an easily recognized species either in fruit or when sterile. The leaf blade has a bristle tip and five or fewer veins. Those characters combined with the usual absence of nodal glands will separate this species from all other North American linear-leaved species. Ecologically, it is consistently found in more alkaline waters than any other North American pondweed. A study of 35 localities established the mean to be 124.1 mg/l CaCO3 (C. B. Hellquist 1984). (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. capillaceus | P. porteri |
Name authority | Rafinesque: Medical Repository hexade 2, 5:354. (1808) | Morong: Botanical Gazette 6: 290, fig. 3. (1881) |
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