3. Stuckenia pamirica (Baagøe) Z. Kaplan, Folia Geobot. 43: 194. 2008.
长鞘菹草 chang qiao zu cao
Potamogeton pamiricus Baagøe, Vidensk. Meddel. Naturhist. Foren. Kjøbenhavn 1903: 182. 1903; P. recurvatus Hagström.
Plants perennial, submerged. Rhizomes terete, slender to robust. Stems terete, slender. Stipules partly fused with leaf base and sheathing stem; sheaths 1.8-5 cm, convolute, appearing as a short spiral when transversely dissected, usually dark green to blackish with creamy yellowish to whitish margins; ligule whitish, 1-2.3 cm, persistent; leaves sessile, dark green or mostly conspicuously dark brown to blackish when dried, older ones discolored, creamy whitish or grayish to bright white, blade occasionally recurved at top, linear, 7-26 cm × 0.3-1.7 mm, 3-veined, with air channels bordering midvein, apex obtuse. Spikes terminal, with 4-6 whorls of opposite flowers; peduncles 2.5-3.5 cm. Fruit obovoid, 3.5-4.2 × ca. 2 mm, abaxial keel obtuse, with a very short, verruciform or cusped beak.
Submersed in lakes. Qinghai, Xizang [Kyrgyzstan, Tajikistan].
The species here called Stuckenia pamirica was generally treated under the name Potamogeton recurvatus. The name P. pamiricus was widely misapplied to broad-leaved forms of S. filiformis, and for this reason, all records in the literature are doubtful.