2. Najas gracillima (A. Braun ex Engelm.) Magnus (slender naiad)

Pl. 110 a, b; Map 451

Stems 5–50 cm long. Leaves 0.5–3 cm long, 0.1–0.5 mm wide, ascending to spreading, minutely serrulate with 1‑celled teeth usually visible only with magnification, the tip acute to acuminate. Leaf bases abruptly broadened into stipular sheaths, the sheaths auriculate. Seeds 2.0–3.2 mm long, narrowly fusiform to cylindrical, curved to 1 side at the tip, the surface light brown, dull, finely pitted with 25–40 indistinct rows of more or less square pits. July–September.

Scattered in southern and eastern Missouri (eastern U.S. and Canada west to Minnesota, disjunct in California). Submerged aquatic in ponds, particularly in sinkhole ponds.