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Ogden's pondweed, potamot d'Ogden

northern snail-seed pondweed, potamot spirille, spiral pondweed

Rhizomes

absent.

present.

Cauline stems

compressed-filiform, without spots, to 50 cm;

glands green, golden brown to dark brown, 0.2–0.6 mm diam.

compressed, without spots, 5–40 cm;

glands absent.

Turions

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.

absent.

Leaves

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).

both submersed and floating or floating absent, ± spirally arranged.

Floating leaves

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 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;

peduncles not dimorphic, terminal or occasionally axillary, erect or rarely recurved, slightly clavate, 1–3 cm;

spikes not dimorphic, cylindric, 5–11 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, 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.

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.

Chromosome number

unknownnot available.

Potamogeton ogdenii

Potamogeton spirillus

Phenology Flowering mid summer–fall. Flowering mid summer–late fall.
Habitat Alkaline waters of ponds and lakes Neutral to acidic waters of ponds, lakes, and streams
Elevation 100–300 m (300–1000 ft) 0–400 m (0–1300 ft)
Distribution
from FNA
CT; MA; NY; VT; ON
from FNA
CT; IA; MA; ME; MI; MN; NE; NH; NJ; NY; OH; PA; RI; VT; WI; MB; NB; NF; NS; ON; PE; QC
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Discussion

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.)

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 Potamogetonaceae > Potamogeton Potamogetonaceae > Potamogeton
Sibling taxa
P. alpinus, P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. epihydrus, P. floridanus, P. foliosus, P. friesii, P. gramineus, P. groenlandicus, P. hillii, P. illinoensis, P. natans, P. nodosus, P. oakesianus, P. oblongus, P. obtusifolius, P. perfoliatus, P. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. spirillus, P. strictifolius, P. subsibiricus, P. tennesseensis, P. vaseyi, P. zosteriformis
P. alpinus, P. amplifolius, P. bicupulatus, P. clystocarpus, P. confervoides, P. crispus, P. diversifolius, P. epihydrus, P. floridanus, P. foliosus, P. friesii, P. gramineus, P. groenlandicus, P. hillii, P. illinoensis, P. natans, P. nodosus, P. oakesianus, P. oblongus, P. obtusifolius, P. ogdenii, P. perfoliatus, P. praelongus, P. pulcher, P. pusillus, P. richardsonii, P. robbinsii, P. strictifolius, P. subsibiricus, P. tennesseensis, P. vaseyi, P. zosteriformis
Name authority Hellquist & R. L. Hilton: Systematic Botany 8: 88, figs. 1–3, plates 1–2, figs. 1–3. (1983) Tuckerman: American Journal of Science, and Arts ser. 2, 6:228. (1848)
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