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Key to Potamogeton, Key C: pondweeds with connate leaves and submersed leaves 10-58 mm wide
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https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&keyid=39495
3 Leaf apex boat-shaped (curved upward adaxially), splitting when pressed; stipules usually persistent, conspicuous; rhizomes with rusty-red spots; [n. PA northward] | |
4 Leaves orbicular to ovate, often lanceolate in soft water, 1-6 cm long, with 3-25 delicate veins; stipules deteriorating and deciduous (otherwise delicate and lacking fibers), absent on lower portions of stem | |
4 Leaves ovate-lanceolate to narrowly lanceolate, 1.6-13 cm long, with 3-35 coarse veins; stipules disintegrating to persistent fibers, even on lower portions of stem | |
5 Submersed leaves with petioles 1-13 cm long. | |
9 Submersed leaf blades typically reddish-green colored (especially upon drying), with 7 veins (sometimes with 6 additional obscure veins) and a conspicuous reticulate pattern along midvein; fruit stalked, turgid; [NJ and PA, northward] | |
9 Submersed leaf blades green or brownish-green, with 7-19 (P. illinoensis) or 3-9 conspicuous veins (P. gramineus), without a reticulate portion along midvein; fruit sessile, laterally compressed; if submersed leaves with < 7 veins, then leaves typically 1.5-4.5 cm long and and stipules acute; [collectively widespread]. | |