Stuckenia filiformis subsp. occidentalis
Stuckenia
potamot filiforme occidental, slender-leaf pondweed, western fineleaf pondweed, western pondweed
pondweed, potamot
20–100 cm.
terete, nodes without oil glands.
stipules disintegrating with age, those on proximal portion of stem inflated;
blade inflated; 0.2–5 mm wide.
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.
peduncles with flower and/or fruits adjacent or separated by less than 2 cm.
spikes, capitate or cylindric, submersed;
peduncles flexible, not projecting inflorescence above surface of water.
pistils 4.
often absent.
abaxially rounded, beaked or not, turgid;
embryo with less than 1 full coil.
= 13.
Stuckenia filiformis subsp. occidentalis
Stuckenia
In the Great Lakes region, the name Potamogeton [Stuckenia] vaginatus has often been misapplied to this taxon. The distribution of S. vaginatus is further to the north and west than the Great Lakes region, however. Stuckenia filiformis subsp. occidentaliis rarely produces fruit in the eastern portion of its range, while to the north and west it commonly fruits. This subspecies is very similar to Potamogeton rostratus Hagström ([the combination does not exist within the genus Stuckenia)] of Asia and may prove to be the same taxon. Both grow in similar habitats. The proximal stipules are much enlarged and inflated, and the leaves are generally wider than the other subspecies.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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.)
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 |
BC
MI Flora
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