Potamogeton clystocarpus |
Potamogeton richardsonii |
|
---|---|---|
little aguja pondweed |
clasping-leaf pondweed, potamot de Richardson, Richardson's pondweed |
|
Cauline stems | terete to slightly compressed, without spots, to 57 cm; glands white to gold, 0.2–0.3 mm diam. |
terete, without spots, to 100 cm; nodal 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). |
submersed, ± spirally arranged, sessile, lax; stipules persistent, conspicuous, convolute, free from blade, white, not ligulate, 0.12–0.17 cm, fibrous, disintegrating to persistent fibers, even on proximal portion of stem, shredding at apex, apex obtuse; blade olive green, ovate-lanceolate to narrowly lanceolate, not arcuate, 1.6–13 cm × 5–28 mm, base rounded, without basal lobes, clasping, margins entire to crispate, apex not hoodlike, not splitting when pressed, acute to obtuse, lacunae absent; veins 3–35. |
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. |
emersed, unbranched; peduncles not dimorphic, terminal or axillary, erect to rarely recurved, clavate, 1.5–14.8 cm; spikes not dimorphic, cylindric, 13–37 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, obovoid, turgid to concave, not or rarely abaxially keeled, not laterally keeled, 2.2–4.2 × 1.7–2.9 mm; beak erect, 0.4–0.7 mm; sides without basal tubercles; embryo with 1 full spiral. |
Rhizome(s) | absent. |
present. |
2n | = 52. |
|
Potamogeton clystocarpus |
Potamogeton richardsonii |
|
Phenology | Flowering and fruiting spring–summer. | Flowering summer–fall. |
Habitat | Small streams | Alkaline waters of lakes, streams, and rivers |
Elevation | ca. 1800 m (ca. 5900 ft) | 0–3000 m (0–9800 ft) |
Distribution |
TX |
AK; CA; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NV; NY; OH; OR; PA; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NS; NT; ON; QC; SK; YT
|
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 richardsonii is quite similar to P. perfoliatus. Specific characteristics to separate the two species are the shape of the leaf blade apex, acute in P. richardsonii and obtuse in P. perfoliatus, and the condition of the stipules, disintegrating between the veins leaving fibrous strands in P. richardsonii, and the entire stipule, including the veins, disintegrating in P. perfoliatus. Two hybrids, Potamogeton gramineus × P. richardsonii (= P. × hagstroemii A. Bennett [as hagstromii]) and P. nodosus × P. richardsonii (= P. × rectifolius A. Bennett), have been described. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | P. perfoliatus var. richardsonii, P. perfoliatus subsp. richardsonii | |
Name authority | Fernald: Memoirs of the american academy of arts and science n.s. 17:79, plates 15, 30, fig. 5. (1932) | (A. Bennett) Rydberg: Bulletin of the Torrey Botanical Club 32: 599. (1905) |
Web links |
|