Potamogeton clystocarpus |
Potamogeton bicupulatus |
|
---|---|---|
little aguja pondweed |
snail-seed pondweed |
|
Rhizomes | absent. |
present. |
Cauline stems | terete to slightly compressed, without spots, to 57 cm; glands white to gold, 0.2–0.3 mm diam. |
compressed, without spots, 10–25 cm; glands absent. |
Turions | unknown. |
absent. |
Leaves | submersed, ± spirally arranged, sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, brown, not ligulate, to 0.62 cm, not fibrous, not shredding at tip, apex obtuse; blade green, linear, not arcuate, 3.2–7.8 cm × 0.7–1.7 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute, lacunae rarely absent, in 0–4 rows each side of midrib; veins 3(–5). |
both submersed and floating or floating absent, ± spirally arranged. |
Floating leaves | petiolate; petioles continuous in color to apex, 5–35 mm; blade adaxially light green, lanceolate-elliptic to broadly elliptic, 0.6–2.3(–2.8) cm × 1–11 mm, base tapering or rounded, apex acute to long tapering; veins 3–7. |
|
Submersed leaves | sessile, lax; stipules persistent to deliquescent, inconspicuous, convolute, adnate to blade for less than ½ stipule length, light green, ligulate, 0.2–1.2 cm, not fibrous, not shredding at tip, apex obtuse; blade light green to rarely brown, linear-setaceous, not arcuate, 1.5–11 cm × 0.1–0.4(–0.6) mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, tapering, lacunae absent; veins 1. |
|
Inflorescences | unbranched, emersed; peduncles not dimorphic, axillary or terminal, erect, cylindric, 3.2–4.8 cm; spike not dimorphic, capitate to cylindric, 5.5–7.5 mm. |
unbranched; peduncles dimorphic, submersed axillary, somewhat recurved, clavate, 1–10 mm, emersed axillary or terminal, erect to slightly recurved, slightly clavate, 3.5–22 mm; spikes dimorphic, submersed, globular to ellipsoid, 1.5–7 mm, emersed ellipsoid to cylindric, 3–14 mm. |
Fruits | sessile, brown to yellow-green, obovoid, compressed, abaxially and laterally keeled, 2–2.2 × 1.7–1.8 mm, lateral keels without points; beak erect, 0.5–0.6 mm; sides with 1–3 tubercules near base; embryo with 1 full spiral. |
sessile, greenish brown, somewhat orbicular, compressed, abaxially keeled, laterally keeled, 1.1–2.1 × 1.1–2 mm, lateral keel without points; beak absent; sides without basal tubercles; embryo with more than 1 full spiral. |
Potamogeton clystocarpus |
Potamogeton bicupulatus |
|
Phenology | Flowering and fruiting spring–summer. | Flowering early summer–fall. |
Habitat | Small streams | Acidic waters of ponds, lakes, and streams |
Elevation | ca. 1800 m (ca. 5900 ft) | 0–300 m (0–1000 ft) |
Distribution |
TX |
CT; DE; IN; MA; ME; MI; NH; NY; PA; RI; TN; VA; VT; WI; ON
|
Discussion | Potamogeton clystocarpus is an extremely limited species known from only one canyon in west Texas. Of conservation concern. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Potamogeton bicupulatus is an uncommon species of the acid lakes and streams of northeastern United States and southern Canada. It is the final third species we have with dimorphic inflorescences and embryos with more than one full spiral. It can be separated from the other two, Potamogeton spirillus and P. diversifolius, because it has very narrow submersed leaves without lacunae and fruits with lateral keels without sharp points. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | P. diversifolius var. trichophyllus | |
Name authority | Fernald: Memoirs of the american academy of arts and science n.s. 17:79, plates 15, 30, fig. 5. (1932) | Fernald: Memoirs of the american academy of arts and science 17: 112. (1932) |
Web links |