Potamogeton alpinus
Potamogeton confervoides
alpine pondweed, northern pondweed, potamot alpin, reddish pondweed
alga pondweed, alga-like pondweed, potamot confervoide, Tuckerman's pondweed
terete, without spots, to 200 cm;
nodal glands absent.
terete, without spots, 10–80 cm.
absent.
present, in axils of old leaves and from disintegrating branches, fusiform, 0.7–2 cm, leaves spreading to ascending.
submersed and floating or floating absent, ± 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, 0.1–1.2 cm;
blade reddish green, elliptic or oblanceolate to obovate or oblong-linear, 4–7(–10) cm × 10–25(–40) mm, base gradually tapering into petiole, apex obtuse or acute;
veins (7–)9–13(–15).
sessile, lax;
stipules persistent, inconspicuous, convolute, free from blade, light brown to reddish, not ligulate, (1.2–)1.5–2.5(–4) cm, not fibrous, not shredding at tip, apex blunt;
blade reddish green, oblong-linear to linear-lanceolate, not arcuate, 4.5–18(–25) cm × 5–20 mm, base rounded, without basal lobes, slightly clasping, margins entire, not crispate, apex not hoodlike, obtuse or acute, lacunae in 0–6 rows each side of midvein;
veins 7–9.
unbranched, emersed;
peduncles not dimorphic, terminal or axillary, erect, cylindric, 3–10(–16) cm;
spikes not dimorphic, cylindric, 10–35 mm.
unbranched, emersed;
peduncles not dimorphic, terminal, ascending, somewhat clavate, (3–)5–25 cm;
spikes not dimorphic, capitate, 5–12 mm.
pedicellate, tawny olive-green, obovoid, plump, turgid, abaxially keeled, laterally keeled or not, (2.5–)3–3.5 × (1.7–)2–2.4 mm, lateral keels when present without points;
beak abaxially curved, 0.5–0.9 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.
present.
obvious.
= 52.
Potamogeton alpinus
Potamogeton confervoides
Plants of Potamogeton alpinus often are red whenever taken from the water, a feature that makes this species quite distinctive.
Two varieties, Potamogeton alpinus var. tenuifolius and var. subellipticus, have been recognized in North America, based mainly on submersed leaf shape. Plants bearing both leaf types have been observed in the same population; hence the varieties are not recognized.
Four hybrids, Potamogeton alpinus × P. nodosus (= P. ×subobtusus Hagström), P. alpinus × P. gramineus (= P. xnericius Hagström), P. alpinus × P. praelongus (= P. ×griffithii A. Bennett), and P. alpinus × P. perfoliatus (= P. ×prussicus Hagström), have been described.
(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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