Potamogeton vaseyi
Potamogeton confervoides
potamot de Vasey, Vasey's pondweed
alga pondweed, alga-like pondweed, potamot confervoide, Tuckerman's pondweed
absent.
obvious.
terete, without spots, 2–5 cm;
glands absent.
terete, without spots, 10–80 cm.
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.
present, in axils of old leaves and from disintegrating branches, fusiform, 0.7–2 cm, leaves spreading to ascending.
submersed, or both submersed and floating, ± spirally arranged.
submersed, ± spirally arranged, flaccid, sessile;
stipules deliquescent, inconspicuous, convolute, free from blade, pale green, not ligulate, 0.5–1.2 cm, not fibrous, not shredding at tip, apex obtuse;
blade pale green, linear, not arcuate, 1.8–6.5 cm × 0.1–0.5 mm, base slightly tapering, without basal lobes, not clasping, margins entire, not crispate, apex not hoodlike, extremely attenuate, bristly, lacunae present, each side of midvein to margins;
veins 1.
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.
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).
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.
unbranched, emersed;
peduncles not dimorphic, terminal, ascending, somewhat clavate, (3–)5–25 cm;
spikes not dimorphic, capitate, 5–12 mm.
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.
sessile, light green, round-obovoid or nearly orbicular, compressed, abaxially and laterally keeled, 2–3 × 1.7–2.8 mm, lateral keels without sharp point;
beak erect, 0.5 mm;
sides without basal tubercles;
embryo with less than 1 full spiral.
apparently unknown not available.
= 28.
Potamogeton vaseyi
Potamogeton confervoides
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.)
Potamogeton confervoides is most uncommon and found only in fairly acidic waters. It is easily recognized by its linear, bristly leaves and the unusually long peduncle that seems out of place on a plant with such fine leaves. The leaves are so fine that they almost appear as greenish colored hair in the water. When the plant is removed from the water, the leaves are extremely flaccid leaves and essentially collapse onto each other.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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