Stuckenia
Stuckenia striata
pondweed, potamot
broadleaf pondweed, Nevada-pondweed, striped pondweed
terete, nodes without oil glands.
branched distally, terete to 5-ridged, to 200 cm.
submersed, alternate, opaque, sessile, linear, channeled, turgid, acute at base acute, margins entire, apex obtuse to acute, veins 1–5;
stipules not tubular, adnate to base of leaf blades for 2/3 or more length of stipule, extending past adnation as free ligule.
length and width of those on main stem 2 times or more those on branches;
stipules with stipular sheaths not inflated, 1.2–3.4 cm, ligule 0.2–1.1 cm;
blade linear, 5–21 cm × 0.4–5.1 (–8.5) mm, apex apiculate, cuspidate, or rarely round;
veins 3–5.
spikes, capitate or cylindric, submersed;
peduncles flexible, not projecting inflorescence above surface of water.
peduncles axillary, rarely terminal, erect to ascending, cylindric, 1.2–5.2 cm;
spikes cylindric, rarely moniliform, 13–45 mm;
verticels 4–9.
pistils 4.
abaxially rounded, beaked or not, turgid;
embryo with less than 1 full coil.
brown to reddish brown, obovoid to oblanceoloid, 3–3.9 × 2.8–3 mm;
beak toward abaxial margin, erect or rarely recurved to apex, 0.2–0.3 mm.
apparently unknown.not available.
= 13.
Stuckenia
Stuckenia striata
The stipules of Stuckenia are adnate to the blade for two-thirds to nearly the entire length of the stipule. The few species of Potamogeton with adnate stipules have the adnation less than half the length of the stipule, in fact, less than 4 mm. Submersed leaves of Potamogeton are translucent, flat, and without grooves or channels, whereas those of Stuckenia are opaque, channeled, and turgid.
A proposal to elevate Potamogeton subgenus. Coleogeton to the generic level, retaining the name Coleogeton, was presented (D. H. Les and R. R. Haynes 1996). Potamogeton pectinatus Linnaeus was chosen as the nomenclatural type. The name Stuckenia had been previously published, however, and P. pectinatus cited (C. Börner 1912), making the generic name Coleogeton superfluous. Stuckenia is the correct name, and the appropriate specific combinations have been made (J. Holub 1997).
Species ca. 6 (4 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Stuckenia striata is widespread, although not common, in the western United States, extending southward into Argentina and Chile. Potamogeton latifolius [no combination in Stuckenia has been proposed] was accepted by R. F. Thorne (1993b). After examining specimens throughout the range and studying dozens of populations in the field, we have determined that the two names represent the same taxon. We are placing P. latifolius in synonymy.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaf apex acute, apiculate, cuspidate, rarely round; proximal stipular sheaths not inflated; stems abundantly branched, especially on distal portions; fruits distinctly beaked. | → 2 |
1. Leaf apex notched, obtuse, or round, rarely apiculate; proximal stipular sheaths often inflated; stems sparsely branched on distal portions; fruits without beak. | → 3 |
2. Leaves 0.4–1.5–3(–8.5) mm wide; leaf apex apiculate, cuspidate, or rarely round; plants from restricted range in western United States. | S. striata |
2. Leaves 0.2–1 mm wide; leaf apex acute to mucronate or apiculate; widespread throughout United States and Canada. | S. pectinata |
3. Stipules with distinct ligules to 20 mm, especially on distal stipules; summit of midstem stipules tight to stem, about the ± same width as stem; fruit 2–3 mm. | S. filiformis |
3. Stipules without ligules or these to 2 mm on distal stipules; summit of midstem stipules inflated at least 2 times width of stem; fruit 3–3.8 mm. | S. vaginata |
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