Potamogeton clystocarpus |
Potamogeton vaseyi |
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little aguja pondweed |
potamot de Vasey, Vasey's pondweed |
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Rhizomes | absent. |
absent. |
Cauline stems | terete to slightly compressed, without spots, to 57 cm; glands white to gold, 0.2–0.3 mm diam. |
terete, without spots, 2–5 cm; glands absent. |
Turions | unknown. |
common, axillary, 0.5–2 cm × 0.5–1.2 mm, soft; leaves ± 2-ranked; outer leaves 2–3 per side, base not corrugate, apex acute; inner leaves undifferentiated or rolled into tight, hardened structure. |
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, or both submersed and floating, ± spirally arranged. |
Floating leaves | petioles continuous in color to apex, 5–25 mm; blade adaxially greenish brown, elliptic, spatulate, or obovate, 0.6–1.5 cm × 3–8 mm, base acute, apex obtuse; veins 5–9. |
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Submersed leaves | sessile, delicate; stipules persistent, inconspicuous, convolute, free from blade, green to brown, not ligulate, 0.4–1.2 cm, not fibrous, not shredding at tip, apex attenuate; blade light green, linear-filiform, not arcuate, 2–8 cm × 0.1–1 mm, bases slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, acute to almost bristle-tipped, lacunae present, rarely absent, 0–2 rows each side of midvein; veins 1(–3). |
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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, emersed; peduncles not dimorphic, terminal, ascending in flower, recurved in fruit, cylindric, 5–30 mm; spikes not dimorphic, cylindric or moniliform, 6–8 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, green to brown, obliquely round-obovoid, compressed, abaxially keeled, not laterally keeled, 1.5–2.5 × 1.2–1.6 mm; beak erect, 0.3–0.5 mm; sides without basal tubercles; embryo with 1 full spiral. |
2n | = 28. |
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Potamogeton clystocarpus |
Potamogeton vaseyi |
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Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting summer–fall. |
Habitat | Small streams | Quiet waters of lakes, ponds, and rivers |
Elevation | ca. 1800 m (ca. 5900 ft) | 50–500 m (200–1600 ft) |
Distribution |
TX |
CT; IA; IL; IN; MA; ME; MI; MN; NH; NJ; NY; OH; PA; RI; VT; WI; NB; ON; QC
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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.) |
All of the original material of Potamogeton lateralis Morong, including the collection designated as the lectotype, has been studied (C. B. Hellquist et al. 1988). Every specimen, was a mixed collection of P. pusillus and P. vaseyi. Based on the results of the study, P. lateralis is taxonomically nomenclaturally invalid and should be rejected. Potamogeton vaseyi is an uncommon species that has submersed leaves very similar to P. pusillus subsp. gemmiparus. Floating leaves apparently are present only when the species is fertile, and the species often grows intermixed with that subspecies. Collections are consequently often a mixture of the two taxa. Also, sterile collections of either taxon can easily be mistaken for the other. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 22. | FNA vol. 22. |
Parent taxa | ||
Sibling taxa | ||
Name authority | Fernald: Memoirs of the american academy of arts and science n.s. 17:79, plates 15, 30, fig. 5. (1932) | J. W. Robbins: in A. Gray, Manual of Botany of the Northern United States (ed. 5) 485. (1867) |
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